8- Mutations And Genes Flashcards
1
Q
What is a mutation
A
Any change to the base sequence of dna
2
Q
When can mutations occur
A
Error during DNA replication
3
Q
What can increase rate of mutations
A
Mutagenic agents
4
Q
What are the 6 types of mutations
A
Substitution
Deletion
Addition
Duplication
Inversion
Translocation
5
Q
Substitution mutation
A
One of more bases are swapped for another
6
Q
Deletion mutation
A
One or more bases are removed
7
Q
Addition mutation
A
One of more bases are added
8
Q
Duplication mutation
A
One or more base are repeated
9
Q
Inversion mutation
A
A sequence of bases is revers3d
10
Q
Translocation mutation
A
A sequence of bases is moved form one location in. The genome to another
This could be movement within the same chromosome or movement to a differnt chromosome
11
Q
What determines the polypeptide
A
The order of dna bases in a gene
Determined the sequence of amino acids
12
Q
How does mutation in a gene. Effect a polypeptide
A
Sequence of amino acids change so polypeptide changes
13
Q
Why might a mutation in an enzyme stop it working
A
A change in amino acid sequence may change the final 3D shape of the protein . The active site may change so substrates are no longer complementary so can’t bind
14
Q
Explain how some mutations can cause genetic disorders
A
Inherited disorders caused by abnormal genes or chromosomes
Some mutations can increase the likelihood of developing certain cancers
15
Q
What is a hereditary mutation
A
If a gamete containing a mutation for a genetic disorder or a type of cancer is fertilised it will be present in the new fetus formed
16
Q
Why do not all mutation affect the order of amino acids
A
The degenerate nature of genetic code means that some amino acid are coded for by more than one dna triplet .
This means that not all types of mutation will always result in a change of amino acid sequences of the polypeptide
Eg. Some substitution will still code for the same amino acid and some inversion
17
Q
If a mutation doesn’t cause a change in amino acid order what is it called
A
A silent mutation
18
Q
What mutations cause a frame shift
A
Addition , deletion , duplication
19
Q
Why do Addition duplicated and deletions almost always change amino acid sequence
A
they change the number of bases present
This causes a frame shift
20
Q
Base triplets that follow on from the mutation are said to be …….. of the mutation
A
Downstream
21
Q
When do mutations occur
A
Spontaneously
Eg. When dna is misread during replication
22
Q
Examples of mutagenic agents
A
Ultra violet radiation
Ionising radiation
Some chemicals
Some viruses
23
Q
What 3 ways can mutagenic agents increase rate of mutations
A
Acting as a base
Altering vases
Changing the structure of dna
24
Q
What 3 ways can mutagenic agents increase rate of mutations
Acting as a base
Eg,
A
Chemicals called base analogs can substitute for a base during dna replication . Changing the base sequence in the new DNA
5-bromouracil is a base analog that can substitute for thymine. It can pair with guanine causing a substitution mutation in the new dna
25
What 3 ways can mutagenic agents increase rate of mutations
Altering bases
Eg,
Some chemicals can delete or alter bases
Eg, Alkylating agents can add an alkyl group to guanine which changes the structure so that is pairs with thymine
26
What 3 ways can mutagenic agents increase rate of mutations
Changing the structure of dna
Eg
Some types of radiation can change the structure of dna which.
Causes problems during dna replication
Eg, uv radiation can cause adjacent thymine bases to pair up togetehr
27
Mutations that occur in individual cells after fertilisation are called….
Acquired mutations
28
If an acquired mutation occurs in genes that control rate of cell division ( by mitosis) what can happen
Uncontrolled cell division
29
If a cell divides uncontrollably the results is a ….
Tumour
30
What is a tumour
A mass of abnormal cells
31
When are tumours cancer
Theme they invade and destroy surrounding tissue
32
What are the two types of gene that control cell division
Tumour suppressor genes
Proto-oncogenes
33
Mutations in tumour suppressor genes and proto-oncogenes cause ….
Cancer
34
What happens if a mutation occurs in a tumour suppressor gene
The gene can be inactivated
When functioning normally, tumour suppressor genes slow cell division by product of proteins that stop cell dividing or cause them to self distruct( apoptosis ;
If a mutation occurs in a tumour suppressor gene, the protein isn’t produced. The cells divide uncontrollably , resulting in a tumour
35
What happens if a mutation occurs in a proto-oncogene
The effect of the gene can be increased if a mutation occurs in the dna sequence
When functioning normally , proto-oncogenes stimulate cell division by producing proteins that make cells divide
If a mutation occurs in a proto-oncogene , the gene can become overactive. This stimulated the cells to divide uncontrollably resulting in a tumour
36
What is a mutated proto-oncogene called
Oncogene
37
What are the two types of tumours
Malignant
Benign
38
What is a malignant tumour
Cancers
They usually grow rapidly and invade and destroy surrounding tissues. Cells can break off the rumours and spread to other parts of the body in the blood stream or lymphatic system
39
What is a benign tumour
Non cancerous . They usually grow slower than malignant tumours, and a tee oftern cover in fibourous tissues that stop cells invading other tissues. Benign tumour are oftern harmless , but they can cause bloackages and put pressure on organs
40
Can benign tumours become malignant
Yes
41
How might tumour cells differ to normal cells
1) irregular shape
2)nucleus larger an darker, sometimes the cells have more than one nucleus
3) they don’t produce all proteins needed ot function correctly
4) they have differnt antigens on their surface
5: they don’t respond to growth regulating processes
6) they divide more frequently than normal cells
42
What is methylation
Adding a methyl (CH3) group onto something
43
What is methylating of DNA an important method of
Regulating gene expression - it can control whether or not a gene is transcribed and translated
44
When methylation is happening normally, what does it play a key role in
Many processes in the body
45
WhT is it called if methylation occurs to much
Hypermethylation
46
What is it called when methylation occurs to little
Hypomethylation
47
How can tumour growth be caused by hypermethylation
When tumour suppressor genes are hypermethylated, the genes are not transcribed - so the proteins they produce to slow down cell divison arnt made. Thus means that cells are able to divide uncontrollably by mitosis and tumours can develope
48
How can tumour growth be caused by hypomethylation
Hypomethylation of proto-oncogene chauses them to act as oncogenes - increasing the production of the proteins that encourages cell divison , this stimulated cells to divide uncontrollably which causes the formation of tumours
49
What can increased exposure to oestrogen over an extended period of time cause
Increase risk of developing breast cancer
50
What can u creased exposure to oestrogen be due to
starting menstruation earlier then usual t or menopause later
51
What are the 3 theory’s of how oestrogen can contribute to the development of some breast cancers
1) oestrogen can stimulate certain breast cells to divide and replicate. The facts that more cell divison are taking place naturally increase the chances of mutations occurring m and so increases the chance of cells becoming cancerous
2) This ability to stimulate division could also mean that if cells do become cancerous, their rapid replication could be further assisted by ostrogen, helping tumours to form quickly.
3) Other research suggests that ostrogen is actually able to introduce mutations directly into the DNA of certain breast cells, again increasing the chance of these cells becoming cancerous.
52
Where do all specialised cell come form
Stem cells
53
What are stem cells
Unspecialised cells that can develop into other types of cell
They divide to become new cells which then become specialised
54
T or f
All multicellular organism have some form of stem cells
T
55
Where are stem cells found
Embryo
Some adult tissue
56
What are stem cells found in the embryos for
Become all the specialised cells needed to form the fetus
57
What are stem cells found in some adult tissue for
they become specialised cells that need to be replaced
58
what is a totipotent cell
stem cells that can mature into any time of body cell in an organism
59
when are totipotent stem cells present in mammals
In the first few cell divisions of an embryo
60
After totipotent stem cells, the embryonic stem cells become …..
Pluripotent
61
What are pluripotent cells
They can still specialise into any cell in the body, but lose the ability to become the cells that make up the placenta
62
What 2 types of stem cells are present in adult mammals
Multi potent
Unipotent
63
What are multipotent stem cells
These are able to differentiate into a few differnt types of cells
Eg, red and white blood cells can be formed form them found in bone marrow
64
What are unipotent stem cells
these can only differentiate into one type of cell.
65
How do stem cells specialise
1) stem cells all contain the same genes - but during development not all of them are transcribed and translated
2) under the right conditions, come genes are expressed and other are switched of
3) mRNA is only transcribed form specific genes
4) the mRNA form these genes is then translated into proteins
5) these proteins modify the cell- they determine the cell structure and control cell processes ( including the expression of more genes , which produce more proteins )
6) changes to the cell produced by these proteins cause the cell to become specialised. These changes are difficult to reverse, so once a cell has specialised it stays specialised
66
Explain how stem cells specialise into red blood cells
Red blood cells are produce from a type of stem cells in the bone marrow
They contain lots of heamoglobin and no nucleolus
The stem cells produce a new cell in which th genes for haemoglobin production are expressed, other genes, such as those involved in removing the nucleus , are expressed too.
Many other genes are not exporessed, resulting in specialised RBc
67
What are the heart muscle cells that are up a lot of the tissue in out heart
Cardiomyocytes
68
What was the previous ideas about cardiomyoctes and why is this a problem
That they can’t divide to replicate themselves in mature mamamles
If heart becomes damaged, eg, by heart attack of cell worn out by age.
69
What does recent reasearch about cardiomyocytes show
They do have some regenerative capability
Soem scientists not think that old or damaged cardiomyocytes can be replaced by new cardiomyocytes derived form a small supply of unipotent stem cells in the heart.
Some research think that this process coal be occurring constantly
70
What are the 2 views on how quickly cardiomyocytes regenerate
1- some believe that it’s really slow process and that it’s possible that some cardiomyocytes are never replaces throughout a persons lifetime.
2- others think that it’s occurring more quickly so that every cardiomyocytes in the heart is replaced several times in a lifetime
71
Soem stem cell therapies already exist for some disease affecting,,…
Blood and immune system
72
Explain stem cell therapies for abnormal blood cells
Bone marrow contains stem cells that can become specialised to form any type of blood cell. Blood marrow transplant can be used to replace faulty bone marrow in patients that produce abnormal blood cell. The stem cells in the transplanted bone marrow divide and specialise to produce healthy blood cells
73
What have bone marrow transplants been used to treat
leukaemia
Lumphoma
Genetic disorders such as sickle cell anaemia and severe comined immunodeficiency (SCID)
74
what other diseases COULD stem cells treat
1) spinal cord injuries - stem cells could be used to replace demaage nerve tissue
2) heart disease and damage caused by heart attacks - stem cells could be used to replace damage heart tissue
3) bladder conditions. - stem cells cloud be used to grow while bladders, which are then implanted in patients to replace disease ones
4) respiratory diseases - donated windpipes can be stripped down to their simple collagen structure and then converted with tissues generated by stem cells. This can then be transplanted into patients
5) organ transplants - organs could be grown form stem cells to provide new organs for people on donor wiaiting lists
75
Potential benifits of stem cell therapies
1) save many lives - eg. People waiting for organ transplants die before. Donor organ becomes available. Stem cells could be used to grow organs for those people awaiting transplants
2) they could improve QOL for many people- eg, stem cells could be used to replace damaged cells in the eyes of people who are blind
76
What are the 3 main potential sources of human stem cells
adult stem cells
Embryonic stem cells
Induced pluripotent stem cells(IPS)
77
Where are adult stem cells obtained
From the body tissues of an adult
Eg. Adult tem cells are found in bone marrow
78
How are adult stem cells obtained
Relatively simple operation
With very little risk involved , but quite a lot of dicomfort
79
Negative of adult stem cells
Aren’t as flexible as embryonic stem cells - they can only specialise into a limited range of cells, not all body cell types ( they’re multi potent )
80
Where are embryonic stem cells obtained
From embryos at an early stage of development
81
How are embryonic stem cells obtained
Embryos Created in the lab using IVF
Once the embryos are approximately 4 to 5 days old, stem cells are removed form the, and rest of the embryo are destroyed
82
Positive of embryonic stem cells and what type of cell are they
Divide an unlimited number of times and develope into all types of body cells - pluripotent
83
How are iPS cell created
By scientists in the lab
The process involves ‘reprogramming’ specialised adult body cells so that they become pluripotent
The adult cells are made to express a series of transcription factors that are normally associated with pluripotent cells . The transcription factors cause adult body cells to express genes that are associated with pluripotency
84
What is a way of making transcription factors that cause adult body cell to express genes associated with pluripotency
Infecting them with specifically modified virus.
The virus has the genes coding for fhe transcription factors within its DNA
When the virus infects rhe adult cell, these genes are passed into the adult cells DNA ,, meaning the cell is able to produce the transcription factors
85
Ethical issues surrounding embryonic stem cells
1) obtaining stem cells from embryos created by IVF rashes ethical issues as the procedure results in the destruction of an embryo that could become a fetus if placed in the womb
2) Some people believe that at the moment of fertilisation an individual is formed that has the right to life — so they believe that it's wrong to destroy embryos.
3( Some people have fewer objections to stem cells being obtained from egg cells that haven't been fertilised by sperm, but have been artificially activated to start dividing. This is because the cells couldn't survive past a few days and wouldn't produce a fetus if placed in a womb.
4)Some people think that scientists should only use adult stem cells because their production doesn't destroy an embryo. But adult stem cells can't develop into all the specialised cell types that embryonic stem cells can.
86
benifits of IPS
potential to be as flexible as embryonic stem cells
They’re obtained form adult tissues so arnt the same ethical issues as embryos
Possible to be made form patients own cells, so genetically identical to patients own cells
They could be used to grow some new tissues or and organ that the patients body wouldn’t reject
87
T or f
all the cells in an organism carry the same genes
Yes
88
If all cells in an organism carry the same genes
How come the structure and functions of differnt cells vary
Because not all genes in a cell are expressed
As differnt Genes are expressed, differnt proteins are made and these protien modify the cell
They determine the cell structure and control cell processes
89
The transcription of genes is controlled by protien molecules called ….
Transcription factors
90
Explain how transcription factors control which genes are expressed in eukaryotes
1. Transcription factors move from the cytoplasm to the nucleolus
2. In the nucleus they bind to specific DNA sites near the start of their target genes- the genes they control the expression of
3) they control the expression by controlling rate of transcription
91
What are the 2 types of transcription factors called
Activators
Repressors
92
What do activators (transcription factions) do
Stimulate or increase the rate of transcription
93
Give an example of activators ( transcription factors )
they help RNA polymerase bind to the strat of the target green and activate transcription
94
What do repressors ( transcription factors ) do
Inhibit or decrease the rate if transcription
95
Give an example of repressors ( transcription factors )
They bind to the start of the target gene , preventing RNA polymerase from, brining, stopping transcription
96
The expression of genes can also be affected by other molecules in the cell such as …..
Oestrogen
RNA interference
97
How does oestrogen affect transcription
1) oestrogen is a steroid hormone fhat can affect transcription by binding to a transcription factor called oestrogen receptor, forming an oestrogen-oestrogen receptor complex
2) the complex moved from the cytoplasm into the nucleolus where it binds to specific DNA sites near the start of the target gene
3) the complex can act as an activator of transcription, eg, helping RNA polymerase bind the the start if the target gene
98
What is RNAi (in eukaryotes)
Where small , double stranded RNA Molecules stop mRNA from target genes being translated into proteins,
99
What are the molecules involved in RNAi
siRNA ( small interfering RNA)
miRNA ( microRNA)
100
How does RNAi work in eukaryotes
1) once mRNA has been transcribed p, it leave the ncuelous form the cytoplasm
2) in the cytoplasm, double stranded siRNA associates with several protiens and unwinds. a single strand then bind to target mRNA. The base sequence of the siRNA is complementary to the base sequence in section of the target mRNA.
3) the proteins associated with the siRNA cut the mRNA into fragments - so that is can no longer be translated. The fragments then move into a processing body which contains ‘tools’ to degrade them
101
What is the siRNA equivalent in plants
miRNA
102
Explain miRNA in mammals
in mammals the MI RNA isn’t usually fully complementary to the target mRNA
. This makes it less specific than SI RNA and so it may target more than one mRNA molecule
like siRNA it associates with proteins and binds to target mRNA in the cytoplasm
instead of the proteins associated with miRNA cutting mRNA into fragments, the miRNA protein complex physically block the translation of the target mRNA
the mRNA is moved into a processing body where it can either be stored or degraded when it stored it can be returned and translated at another time
103
siRNA or miRNA
In mamamls
In which one can the mRNA be stored
miRNA
104
In eukaryotes, what can epigenetic control determine
Whether a gene is switched on or off
105
How does epigenetic control work
Through attachment or removal of chemical groups to or form DNA or histone proteins
106
What are the chemical groups that are attached or removed from DNA or histones called _ through epigenetic control
Epigenetic marks
107
Do epigenetic marks alter the base sequence of DNA
No
108
What do epigenetic marks alter
how easy it is for the enzyme and other proteins needed for transcription to interact with and transcribe the DNA
109
What do epigenetic changes to gene expression plat a role in
Lots of normal cellular processes
also can occur in response to change in the environment
110
Organisms inherit their DNA base sequences from their….
Parents
111
What happens to epigenetic marks on DNA between generations
Most are removed
But some escape the removal process and are passed on to offspring
112
Some epigenetic marks on dna arnt removed between generations
What does this mean fir the offspring
The expression of some genes in the offspring can be affected by environmental changes that affect their parents or grandparents
113
What two ways can genes be switched of in epigenetic control
Increased methylation
Decreased acetylation of histones
114
What is methylation of DNA
When a methyl group is attached to the dna coding for a gene
115
Where does the methyl group always attach in methylation of DNA
The CpG site
116
What is a CpG site
Where cytosine and guanine bases are next to each other in the DNA
117
How does methylation effect DNA
Changes the structure so that the transcriptional machinery (enzymes, protines ect ) can’t interact with the gene - so the gene is not expressed
118
What makes up chromomes
DNA wraps around histones to from chromatin which makes up chromomes
119
Chromatin can be a highly or less condensed. What does this effect
How condensed it is affects the accessibility of the DNA and whether or not us can be transcribed
120
How can histones be epigenetically modified
By the addition or removal of acetyl groups
121
Give 2 examples of epigenetic marks
acetyl groups
Methyl group
122
What happens when histones are acetylated
The chromatin is less condensed
This means that the transcriptional machinery can access the DNA allowing genes ot be transcribed
123
What happens when acetyl groups are removed from the histones
The chromatin becomes highly condensed and genes in the DNA can’t be transcribed because the transcriptional machinery can’t physically access them
124
What enzymes are responsible for removing the acetyl groups
Histone deacetylase (HDAC)
125
What are epigenetics
Changes involve inheritable , reverisble changes to DNA that effect whether genes are transcribed or not
126
What do histones do
Structural support for dna
Can be modified by acetylation to regulate gene expression
127
Does methylated DNA cause more or less expression amd why
Less and more tightly packed
128
What is an acetyl group
COCH3
129
What is euchromatin
And what’s it caused by
Acetylation
Regions with high transcriptional activity are loosely packed
130
What is heterochromatin caused by
Methylation
regions of low or no transcriptional activity are densely packed
131
What feature makes epigenetic changes good targets for new drugs to combat diseases
They are reversible
132
Increased methylation can lead to a gene being switched off
How can drugs be used in this scenarios
Drugs that stop methylation can sometimes be used to treat disease caused this way
Eg. Azacitidine is used in chemotherapy for types of cancer that are caused by increased methylation of tumour suppressor genes
133
Decreased acetylation of histone can lead to genes being switched off
How can drugs play a part in this
HDAC inhivitorcdrugs
Can be used to treat disease that are caused in this way
These work by inhibiting the activity of histone deacetylade ( HDAC) enzyme, which are responsible for removing the acetyl group form histones. Without the activity of HDAC enzymes, the gene remains acetylated and the proteins they code for can be transcribed
134
What is the problem with developing drugs to counteract epigenetic changes
these changes take place normally in a lot of cell, so the drugs need to be as specific as possible
135
What is the phenotype of an organism the result of
The organisms genotype and the interaction of its genotype with the environment
136
How is overeating an example of beinf effected by genes and environment
Environment - increased ability of food
Gene- later discovered food consumption increased dopamine levels , once enough dopanime was released people would stop eating. Reasearch discovered that people with one particals allele has 30% fewer dopamine receptors. People with this more likely to overeat
137
What studies are usefull when tryin g to determine what’s due to environmental factors and what’s due to genetic factors
Twin studies
138
How are twin studies useful to determine influenced on phenotype
Twins are genetically identical so any differnce in phenotype must be due to environemtnal factors. If a characteristic is very similar in identical twins , genetics probably plays as the most important role, but if a characteristic is differnt between the twins the environemnt must have a larger influence
139
How can cancers be caused genetically
Some cancers are linked with specific inherited alleles. If you inherit that allele your more likely o get that type of cancer
140
How can cancer be caused environmentally
Exposure to radiation , lifestyle choices such as smoking , increased alcohol consumption and a high fat diet have all been linked to an increase chance of developing some cancers
141
What is cancer a mutation in
Proto-oncogenes
tumour suppressor genes
142
Why is it usefull if specific cancer causing mutations are known in terms of prevention
With the example of breast cancer
Then it’s possible to screen for the mutation in a persons DNA - can screen for BRCA1 tumour suppressor gene wich increases chance of breast cancer
Knowing. About increases risks means that preventative steps can be taken to reduce it
For example a woman may have a mastectomy or be screened for breast cancer more often to increase chances of an early diagnosis
knwoung about specific mutations also means more sensitive tests can be developed which can
Lead to earlier and more accurate diagnosis
143
Why is it usefull if specific cancer causing mutations are known in terms of treatment
Useful in developing drugs that effectively target them .
Some cancer causing mutations require more aggressive treatment than others so understanding how the mutation that causes them works can help produce the best treatment plant.
Gene therapy may also be able to retreat cancer caused by some mutations.
144
What is a genome
The entire set of DNA, including all the gene in an organism
145
what allowed us to sequence the genomes of a variety of organisms form bacteria to humans
Improvements in technology
146
Gene sequencing methods only work on …..
Fragments of dna
147
What do you need to do if you want to sequence the entire genome of an organism
Chop into smaller pieces first
the smaller pieces are sequences and then put back in order to give the sequence of the whole
genome
148
When was the human genome project competed and what do they do
2003
Mappend the entire sequence of the human genome for the first time
149
What is a proteome
all the proteins that are made by an organism
150
How much non coding dna do simple organisms like bacteria have
Not much
151
why is it easy to determine proteome from dna sequence of simple organisms genome
They don’t have much non coding dna
152
Why would it be useful to know the proteome of a bacteria
Identifying protien antigens on the surface of disease causing bacteria can help develop vaccines to prevent these diseases
153
Why is it harder to translate the genome of complex organisms
They have large sections of non coding DNA
contain complex regulatory genes which determine when the genes that sore for particular proteins should be switch3d on and off
This makes it difficult to translate their genome unit their proteome Because it’s harder to find the buts that code for proteins among the non coding and regulatory dna
154
Exmplaim how sequencing methods have been updated
In thepast, many sequencing methods were labour intensive, expensive and could only be done on a small scale. Not they are oftern automated, more cost effective and can be done on a very large scale
155
What is an example of an updated sequencing technique
Pyrosequecning is recently developed technique that can sequence around 400 million bases in a10 hour period
156
What is a proteome
All the proteins that are expressed
157
cant we transfer knowledge of the genome to the proteome in more complex organisms?
WhyContain introns so we don’t know which parts are coding and which arnt
158
How could knowing the genome help under a stand evolutionary relationships
Q sequence genomes and cross compare, the more separated on the evolutionary tree the less similar the ge
159
How could knowing the genome help with personalised medicine
identify disease before they start showing, Taylor medical care to specific patients, sequence genome allows us to identify where a mutation occurs in a gene in order to target with specific drugs ( this will be different from patients to patients), finding severe immune problems in a baby
160
how could understanding the genome improve agriculture
understanding genome means altering for the benefit of crops
161
Ethical conservations of the genome project
Having Someone’s genome opens up options of exploiting someone’s genome. Such as cloning, designing babies , would be only available to the rich , playing ‘god ‘ in religious arguments
However, positively could scan for genetic diseases which could be removed before birth
162
Gene definition
Section of DNA that codes for a specific protein / characteristic
163
What 3 ways can fragments of can be produced
Reverse transcriptase
Restriction enzymes
Gene machine
164
Where are restriction enzymes from
Bactria
Most likely evolved as a defence against viruses that infect bacteria
165
What 2 ways do restriction enzymes cut dna
Blunt ends
Sticky ends
166
How could a restriction enzyme cut DNA in a sticky end
an end with a bit of DNA that is single stranded.
in order to do this the restriction site must be palindromic , ie the sequence of bases must be the same forward on one strand and backwards on the complimentary strand
167
What feature of DNA allows gene technology to work
DNA sequences are universal so allows gene technology to work
( all organisms are coded for by the same 4 base Paris )
168
b. Why might producing a DNA fragment using reverse transcriptase be advantageous compared to using restriction enzymes?
in general fragments from a eukaryotic. Cell and is made by cutting NDA with restriction enzymes it will contain introns and exons. If it is places into prokaryotic cells to transform them they cannot splice the RNA to removed the introns. If the gene fragment is made using reverse transcriptase there will not be any introns
169
A Gene machine can produce small lengths of DNA called….
Oligonucleptides
170
What does recombinant DNA technology involve
transferring a fragment of DNA from one organism to another
171
Why can transferred DNA fragment from one organism to another work
Genetic code is universal, and because transcription and translation mechanisms are pretty similar too. So the transferred DNA can be used to produce a protein in the cell of the recipient organism.
172
Does recipient and donor organisms of DNA fragment, need to be form the same species
No
173
What are organisms that contain transferred DNA are known as
Transgenic organisms
174
In order to transfer a gene form one organism to another what do you need to do first
Get to a DNA fragment containing the gene your interested in
175
Why is mRNA of a gene easier to obtain than DNA of a gene
Most cells only contain two copies of each genes making it difficult to obtain a DNA fragment contained th etraget gene . But they contain many mRNA molecules wich are complete art to the gene , so mRNA is easier to obtain
176
How can mRNA be used in the reverse transcriptase method to get a dna fragment
1) the mRNA molecule can be used as templates to make lots of dna. Reverse transcriptase enzyme makes dna form an rna template. This is called complimentary DNA
2) mRNA is first isolated, then mixed with free DNA nucleotides and reverse transcriptase. The reverse transcriptase use the mRNA as a template to synthesise a new stand of cDNA , the free dna nueclotides are joined up with DNA polymerase
177
what do some dna have that restriction endonucelase enzymes utilise
Some sections of DNAhave palindromic sequecnes of nucleosides, these sequecnes consist of antiparralel base pairs ( base pairs that read the same in opposite directions)
178
What does restriction endonuclease do
recognise specific palindromic sequecnes ( known as recognition sequences and cut ( digest( the DNA in these places
179
Why do different restriction endonuclease cut at differnt specific recognition sequence nes
Beacuse the shape of the recognition sequences is complementary to the enzyme active site
180
If recognition sequecnes are present at either side of the DNA fragment you want , what can you do
Use restriction endonuclease to separate it from the rest of the DNA
181
How is restriction endonuclease enzyme do
The DNA sample is incubated with the specific restriction endonuclease wich cuts dna fragments out via a hydrolysis reaction
182
Sometimes the cut of restriction endonuclease enzymes leaves sticky ends, what are sticky ends
Small tails of unpaired bases at each end of fragments
183
What can sticky ends be used to do after creating fragments with restriction endonuclease enzymes
Sticky ends can be used to bind ( anneal) the DNA fragment to another piece of DNA that had sticky ends with complemaryy sequecnes
184
What does the gene machine do
fragments of DNA can be synthesied from scratch , without the need of a pre existing DNA template .
This data has contains the necessary information to produce a DNA fragment
185
When using a gene machine do the DNA sequecnes being made have to exist naturally
No
186
How does the gene machine work
The sequence that is required is designed ( if one doesn’t already exist (
The first nucleotide un the sequence is fixed to come sort of support ( eg, a bead)
Nucleotides are added step by step in the correct order, in a cycle of processes that include adding protecting groups. Protecting groups make sure that the nucleotides are joined at the right points, to prevent unwanted branching
Short sections of DNA called oligonucleotides roughly 20 nucleotides long are produced . Once these are complete they are broken off from the support and all the protecting groups are removed, the oligonucelotides can then be joined together to make longer DNA fragments
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Once you have isolated your DNA fragments, what do you need to do
Amplify it so you gave sufficient quantity to work with
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How you amplify dna fragments
In vivo cloning
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What is in vivo cloning
Where copies of the DNA fragment are made inside a living organism
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What are the basic steps of amplifing DNA fragments in vivo cloning
1) the dna fragment is inserted into a vector
2) the vector transfers the dna fragments into host cells
3) identifying transformed host cell
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What is a vector
Something that’s used to transfer dna into a cell
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Examples of vectors that dna fragments can be inserted into
Plasmids or bacteriophages
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What are bacteriophages
Viruses that infect bacteria
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How are dna fragments inserted into a vector
1) the vector dna is cut ions using the same restriction endonuclease that was used to isolate the dna fragment. So the sticky ends if the vector are complementary to the sticky ends of the dna fragment containing the gene
2) the vector dna and dna fragment ar mixed together with dna ligase. Joining sticky ends of dna fragment to sticky end of vector dna
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What does dna ligase do
Joins the sticky end of the dna fragment ot the sticky end of the vector dna
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What is the name of the process of joining dna fragment sticky end to vector dna sticky end using dna ligase
Ligation
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what is the name of dna that is a combination of bases in dna ( vector and fragment dna(
Recombinant dna
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Once the dna fragment is inserted into the vector what does the vector do
Transfer the dna fragment into the host cell
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Vector to host cell ( dna fragment )
What happed if a plasmid vector is used
Host cells have to be persuaded to take in the plasmid vector and its dna
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Vector to host cell ( dna fragment )
What happed if a bacteriophage vector is used
The bacteriophages will infect the host bacteria by injecting its DNA into it . The phage dna then integrates into the bacterial dna
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The host cell that takes up the vectors containing the genes of interest are said to be….
Transformed
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Why do you have to identify which cells have been transformed
Only around 5% will take up the vector and it’s dna
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What can be used to identify transformed cells
Marker genes
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How can marker genes be used to identify transformed cells
Marker genes can be inserted into vectors at the same time as the gene to be cloned. So any transformed host cell will contain the gene to be cloned and the marker cell
Host cells grown in agar plate . Each divides and replicates its dna, transformed cells will produce colonies where all the cells contain the cloned gene and marker gene
The marker gene can code for antibiotic resistance - host cells are brown on agar plate containing the specific antibiotic , so only transformed cells that have the marker gene will survive and grow
Identifies transformed cells are allowed to grow more producing lots of copies of cloned gene
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The marker gene can code for antibiotic resistance - host cells are brown on agar plate containing the specific antibiotic , so only transformed cells that have the marker gene will survive and grow
What else could be used to identify transformed cells
Marker gene could code for fluorescence, when the agar plate is placed under vu light only transformed cells with fluoresce
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What do you need to do if you want the transformed host cell to produce the protein coded for by the dna fragment
Make sure the vector contains specific promoter and terminator region
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What are promotor and terminator regions
Promotor regions are DNA sequecnes that tell and enzyme rna polymerase when to start producing mRNA, terminator regions tell it when to stop
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Why does a transformed host cell need a vector containing the specific promotor and terminator region in order to produce use the protien coded for by the dna fragment
Without the promotor region the dna fragment won’t be transcribed by the host cell and a protien won’t be made
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Promotor and terminator regions might be present in vector dna or…..
They may have to be added in along. With the fragment
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Aside from in vivo how else can dna fragments be amplified
In vitro cloning
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What is in vitro cloning
this is where copies of the Dan fragment are made outside the living organism using the polymerase chain reaction
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What does PCR stand for and what can it be used to do
Polymerase chain reaction
Used to make millions of copies of a fragment of dna in just a few hours
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explain the stages of PCR
1) a reaction mixture is set up that contains the dna sample, free nuceleotides, primers and dna polymerase.
2) dna mixture is heated to 95 °c to break the hydrogen bonds between the 2 dna strands
3) the mixture is then cooled to between 50 and 65 °, so that the primers can bind to the strands
4) the reaction mixture is heated to 72° so DNA polymerase can work
5) dna polymerase lines up free dna nucleotides a
Outside each template strand specific base pairing means new complemenary strands are formed
6) two new copies of the fragment of dna are formed and one cycle of PCR is complete
7) cycle stars again , mixture to 95 , this time all 4 strands (2 origional and 2 new) are used as templates
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What is a primer
Short pieces of dna that are complementary to the bases at the start of the fragment you want
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how many DNA fragments are produced in each PCR cycle
Each is doubled
So
1st = 4
2nd = 8
3rd = 16
Ect
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What type of DNA polymerase is used in PCR
Taq DNA polymerase
(Taq is an enzyme extracted from extremophiles)
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What is the name of the stage in PCR that primers are added
Annealing stag e
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What is the name of the stage in PCR where free nuecloptide are lined up and used to make complementary strands
Extension stage
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Microorganisms plants and animals can all by transformed using recombinant DNA technology. What is the general term for thsi
Genetic engineering
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Transformed organisms are made using …
With the same tech as ….
Recombinant DNA technology
In vivo cloning
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How can transformed plants in produced
A gene that codes for a desirable protien is inserted into a plasmid. The plasmid is added to a bacterium and the bacterium is used as a vector to get the gene into the plant cell. If the right promotor region has been added along with the gene the transformed cell will be able to produce the desired protein
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How can a microorganisms be transformed
Eg, foreign DNA can be inserted into microorganisms to produce lots of usefull protins
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How can an animal be transformed
A gene that codes for a particular desirable protein can be inserted into an early animal embryo or into an egg cell of a female. If the gene is inserted into a very early embryo all the body cells of the resulting transformed animal will end to containing the gene
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What would happen if you insert a gene that codes for a desirable protein into an egg cell
When the female reproduces all the cell of her offspring will contain the gene
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What can the promotor regions that are only activated in specific cell types be used to control
Exactly which of an animal body cells the protien is produced It
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Why might you only want proteins produced in certain cells,
Can be harvested more easily
It produced in the wrong cells could cause damage to the organism
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3 ways transformed organisms could be used
Agriculture
Industry
Medicine
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How can transformed organism be used in agriculture
Higher yield or more nutritious
(So reduce risk of famine and malnutrition)
Pest resistance so fewer pesticides needed, therefore reducing costs and environmental problems associated with pesticides
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What is an example of transformed rice
Golden rice
Contains one gene from a Maisie plant and one for, a soil bacterium. It’s being used to reduce vitamin A deficiency’s
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How are transformed organisms used in industry
Industrial process oftern use biological catalysts. Can be produced by transformed organisms, so can be produced in large quantities, less money
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How are transformed organisms used in medicine
Many drugs and vaccines are produced by transferred organisms, using recombinant DNA technology. They can be quickly, cheaply and in large quantities.
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What are some conserns about using recombinant dna technology in agriculture
Farmers might plant one type of tranfmored crop ( monoculture) thus could make whole crop vunerable to same disease as genetically identical
Monocultures reduce biodiversity
Possibility of superweeds, weeds resistant to herbicides ( could occur is transomfred crops interbreed with wild plants ) then there could be an uncontrolled spread of recombinant DNA with unknown consequences
Organic farmers could have their crops contaminated by wind blown seeds form nearby genetically modified crops. So can’t sell crops as organic and mag lose income
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What are some conserns about using recombinant dna technology in industry
A few large biotech companies control genetic eneginneds. As the use of this technology grows these companies become bigger and may force small companies out of business
Some people think they won’t have a choice about whether to consume food made using genetically engineered organisms
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What are some conserns about using recombinant dna technology in medicine
Companies who own genetic engineering technology may limit the use of technologies that could be saving lives
Some worry this tech could be used unethically ( eg, designer babies)
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How could DNA technology create ownership issues
Some debate on who own genetic material. Is it the donor. Ot the researcher
Large corporations own patents to seeds. They can charge high prices for farmers to purchase
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Why does recombinant DNA technology have many potential humanitarianism benifits
1) agriculture crops could be produced that help reduce the risk of famine and malnutrition
2) transmfored crops could be used to make useful pharmaceutical products which could make drugs available to more people
3) medicines could be produced more cheaply so more can afford the,
4) potential to be used in gene therapy and to treat human diseases
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What is gene therapy
Altering the defective genes inside cells to treat genetic disorders and cancer
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How does genes technology work if the defective gene is caused by 2 mutated recessive alleles
You can add the a working dominant allele to make your for them
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How does genes technology work if the defective gene is caused by a domineering alleal
You can silence the dominant allele
( eg by sticking a bit of DNA in the middle of the allele so it doesn’t work anymore)
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What do both processes of gene therapy involve
Inserting a DNA fragment into the persons original DNA
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How do you get the new allele inside the cell in gene therapy
The allele is inserted into the cell using vectors
Differnt vectors can be used
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What are the 2 type of gene therapy called
Somatic therapy
Germ line therapy
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What is somatic therapy
This involved altering the alleles in the body cells, particularly th cells that are most affected by the disorder,
Eg. It would target the cells lining the lungs in CF
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Does somatic therapy mean offspring would not inherit the disease
No
Somatic therapy doesn’t affect the sex cells so any offspring would inherit the disease
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What is germ line therapy
Involved altering the alleals in the sex cells. So every cells of any offspring produced form these cells will be affected by the gene therapy and they won’t suffer from the disease
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What are some ethical issues with gene therapy
Some people are worried that the technology could be used in ways other than for medical treatment, such as for treating the cosmetic effects of ageing.
Potential to do more harm than good
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What can DNA probs be used for
Locating specific alleles of a gene or to see if a persons DNA contains a mutated Allen that causes a genetic disorder
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What are DNA probs
Show strands of DNA. They have a specific base sequence that’s complementary to the base sequence of part of a target allele
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What does hybridise mean
Bind
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How does a DNA probe work
The DNA probe will bind ( hibridise) to the target allele is its present in the sample, of DNA
A dna probs also has a leble attached to that it can be detected
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What types of labels can be attached to DNA Probs
Radioactive
Fluorescent
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How can a DNA probs be used in electrophoresis
A sample of DNA is digested into fragments using restriction enzymes and separated using electrophoresis
The separated dna fragments are then transferred to a nylon membrane and incubated with fluorescently labelled dna probs
If the allele is present the dna probs will hybridise to it
The memebrane is then exposed to uv light and if the gene is present there will be a fluorescent band.
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aside from electrophoresis, what can dna probes be a part of
DNA microarray
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What is a DNA microarray
A glass slide with microscopic spots of differnt DNA Probes attached to it in rows
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How does DNA microarray work
A sample of fluorescently labels human dna is washed over the array
If the labelled human dna contains any dna sequecnes that match any of the probs it will stick to the array
The array is washed to remove any that hasn’t stuck
The array is then visualised under uv light - any labelled dna attached o a probe will shoe up
So may spots that fluoresces mean that persons dna contain that specific allele
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How do you produce a dna probs
Sequence the allele that you want to screen for. You then use PCr to produce multiple complementary copies of part of the allele
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Uses of screeninf using dna Probes
Help identity inherited conditions so treatment can begin as soon as possible
Help determine how a pateint will respond to a particular drug
Help identify health risks, such as risks of developing certain cancers. If a person new avput these risk they may make differnt lifestyle choices to reduce the risk
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What is genetic counciling
Advising patients and their relatives about the risk of genetic disorders
involves advising people about screening ( such as history of cancer)
Screeninf can identify if someone js a carrier of a mutated allele, the type of mutation and the most effective treatment
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How can screening be used in personalised medicine
Your gene determines how your body responds to certain drugs. Differnt people respond to the same drug in differnt ways - which makes certain drugs more effective for some people than others
Medicines that are tailored to an individuals dna, the theory that if doctors have your genetic information they can predict how you will respond to differnt drugs and only prescribe the ones that will be most effective
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What does VNTR stand for
Variable number tandem repeats
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What is a VNTR
Base sequence that doesn’t code for proteins and repeat next to each other over and over
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Are the number of times the sequecnes of VNTR the same for each person
No
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What is genetic fingerprinting
the number of times a sequence is repeated ( VNTR) AT differnt places can be compared between individuals
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what’s the probability of two individuals having the same genetic fingerprint and why
Very low as low chance of two individuals having the same number VNTR at each place there found in dna
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What technique makes a genetic fingerprint
Electrophoresis
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Explain how to make a genetic fingerprint
1) sample of dna obtained
2) PCR used to make copies of the areas of dna that contain VNTRs , primers are used that bind to either side of these repeats and so whole repeate is amplified
3) end up with DNA fragments where length corresponds to number of repeats that each person has at each specific position
4) fluorescent tag added to fragment so they can be viewed under uv light
5) dna fragemnts under go electrohoresus
6) the dna fragments are views as bands under uv light
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Describe electrophoresis
1) dna mixture placed into wells in a slab of gel and covered in a buffer solution that conducts electricity. An electrical current is passed through gel - dna fragemnts are negativley chmaged so move towards the positive electrode at the far end of the gel
2) small dna fragemnts move faster and travel further through the gel so dna fragemnts sperate according to size
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What 2 uses do genetic fingerprinting have
Determining genetic relationships
Determining genetic variability within a population
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How does genetic fingerprinting help determine genetic relationships
We inherit VNTRs based on our parents
Half from each
So more bands on genetic fingerprints that match the more closely related two people are
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How does genetic variability help determine genetic variability within a population
The greater the number of bands that don’t match on a genetic fingerprint, the more genetically different people are. So you can compare rh number of repeats at several places in the genome for a population to find out how genetically varied a population.
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How is genetic fingerprinting using in forensic science
Compare samples of dna form crime scenes
To samples of dna from possible suspects which could link them to the crime scene
1) dna is isolated from all the collected samples , each sample is replicated using PCr
2) PCr products are run on electrophoresis gel and compared to see a match
3) if samples match links a person to a crime scene
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How can genetic fingerprinting be used in medical diagnosis
can be used to diagnose genetic disorders and cancer. It’s used when the specific mutation isn’t known or where several mutation could have caused the disorder, becasue it identifies broader, altered genetic patterns
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why would you use genetic fingerprinting on animals and plants
To prevent interbreeding which would decrease the gene pool
Interbreeding can lead to an increase risk of genetic disorders leading t o health or reproductibuty problems . So genetic fingerprinting used to see how closely related individuals are .
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Morst recombinant human proteins are generated using eukaryotic cells (e.g., yeast or cultured animal cells) instead of prokaryotic cells
Why?
because eukaryotic cells can perform the post-translational modifications (facilitated by the Golgi apparatus and/or specific enzymes) necessary to produce functional human proteins.
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What are VNTRs
Short, repetitive sequences of DNA that vary greatly amping individuals
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What is genetic fingerprinting
A technique that identifies unique patterns in an individuals dna by analysing VNTRs
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What is a DNA prone
A short dingle stranded sequence of DNA or RNA that is complementary to a target gene or allele used to locate specific sequecnes in a genome
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Use of wells in electrophoresis
Created so you can add dna samples to the wellsn
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What are DNA standards in electrophoresis
Set fragments of DNA
( we know how long each one is )
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What is the solution in electrophoresis
Salt solution / buffer
Free moving charged particles So they conduct electricity
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Why do you need electrodes in electrophoresis s
charges help separate the dna
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What is the overall process for electrophoresis
is extracted from a sample.
2. Restriction Enzyme Digestion: cut DNA into fragments using restriction enzymDNAes that target sequences near VNTRs.
3. VNTR regions are amplified using PCR.
4. DNA fragments are separated using gel electrophoresis.
5. A specific pattern of bands is visualized using radioactive/fluorescent probes.
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What is the hybridisation process
1. Denature target DNA to separate strands.
2. Introduce labelled DNA probes.
3. Allow probes to hybridize (bind) to complementary sequences.
4. Detect bound probes through their labels, indicating the presence of specific alleles.
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what are some applications of hybridisation of dna probes
• Screening for Heritable Conditions: Detect alleles associated with genetic diseases.
• Drug Response Prediction: Identify genetic markers that influence individual responses to medications.
