DNA & the Genome Flashcards
1
Q
What does the DNA helix consist of?
A
Pairs of bases and a sugar phosphate backbone
2
Q
Why is the double helix shape important?
A
It allows DNA to be copied
3
Q
DNA is a what stranded molecule?
A
Double stranded molecule
4
Q
What are the repeating units of DNA called?
A
Nucleotides
5
Q
What do nucleotides consist of?
A
Phosphate
Base
Deoxyribose sugar
6
Q
What element does deoxyribose sugar contain?
A
It contains 5 carbon atoms
7
Q
What are the four different bases called?
A
Adenine
Thymine
Cytosine
Guanine
8
Q
What is the base pair rule?
A
Adenine to thymine
Cytosine to guanine
9
Q
What bonds connect the bases pairs?
A
Weak hydrogen bonds
10
Q
What bonds connect the nucleotides together?
A
Strong Chemical bonds
11
Q
DNA is made up of what strands?
What does this mean?
A
Anti- parallel
It means the run in opposite directions from each other
12
Q
What are the two prime ends?
A
5’ prime
3’ prime
13
Q
What are prokaryotes?
A
Organisms which lack a true membrane-bound nucleus
14
Q
What are eukaryotes?
A
Are organisms which have a membrane bond nucleus which stores their genetic material.
15
Q
What organisms are considered prokaryotes?
A
Bacterial cells
16
Q
What organisms are eukaryotes?
A
Animal, plant and fungal cells
17
Q
Where is the DNA found in a prokaryote?
A
DNA is found in the cytoplasm as a large circular chromosome.
They also have smaller rings of DNA called plasmids
18
Q
Where is the DNA found in a eukaryote?
A
DNA is found tightly coiled into linear chromosomes in the nucleus.
Small circles of DNA can also be found in the mitochondria and chloroplasts.
19
Q
What do some yeast cells contain?
A
Plasmids
20
Q
How do chromosomes fit in the nucleus?
A
It is coiled up in proteins called histones
21
Q
What does DNA replication rely on?
A
It relies on complementary base pairings
22
Q
Why does DNA rely on complementary base pairs?
A
If a strand of DNA is to be copied, it can act as a template.
23
Q
DNA replication is a what controlled process?
A
Enzyme controlled process
24
Q
What two enzymes does DNA replication rely on?
A
DNA polymerase and DNA ligase
25
What do DNA polymerase do?
They catalyse the formation of the bond between the sugar of the nucleotide and the phosphate of the next.
26
What do DNA ligase do?
Joins fragments of DNA together
27
What prime end can the DNA polymerase add to?
3’ end
28
What can DNA polymerase not do?
The cannot start adding nucleotides on its own.
29
What are primers?
Primers are short sections of nucleotides which add to the DNA and the enzyme extends from them
30
In DNA replication what else is required to make a new strand of dna?
Free nucleotides
31
How is the leading strand copied?
Leading strand is made continuously
32
How is the lagging strand copied?
Lagging strand is made in fragments which are then joined together
33
Step one of DNA replication on the leading strand is?
DNA unwinds
34
Step two of DNA replication on the leading strand is?
Hydrogen bonds break and the DNA “unzips”
35
Step three of DNA replication on the leading strand is?
A primer binds to the dna
36
Step four of DNA replication on the leading strand is?
DNA polymerase adds to nucleotides to the 3’ end of the primer
37
Step five of dna replication on the leading strand is?
DNA polymerase catalyses the formation of a chemical bond between nucleotides
38
Step six of dna replication on the leading strand is?
DNA polymerase adds nucleotides to the 3’ end of the growing strand
39
Step seven of dna replication on the leading strand is?
This process is repeated until the entire molecule is replicated.
40
Why does the lagging strand have to be made in fragments?
Due to the leading strand being made continuously because the DNA polymerase constantly add to the 3’ end.
41
Step one of dna replication on the lagging strand is?
A primer binds to the dna once it is exposed
42
Step two of dna replication on the lagging strand is?
DNA polymerase adds nucleotides to the 3’ end of the primer
43
Step three of dna replication on the lagging strand is?
DNA polymerase adds nucleotides to the 3’ end of the growing strand
44
Step four of dna replication on the lagging strand?
DNA polymerase adds nucleotides to the 3’ end of the growing fragment.
A new primer is added to exposed dna.
45
Step five of dna replication on the lagging strand is?
DNA polymerase adds nucleotides to the 3’ end of the primer.
46
Step six of dna replication on the lagging strand?
DNA polymerase catalyses the formation of a chemical bond between nucleotides.
47
Step seven of dna replication on the lagging strand is?
DNA polymerase adds nucleotides to the 3’ end of the growing fragment until it reaches the previous one.
48
Step eight of dna replication on the lagging strand is?
The primer is replaced by dna.
49
Step nine of dna replication on the lagging strand is?
DNA ligase joins the fragments together.
50
Step ten of dna replication on lagging strand is?
As the DNA unzips more, another fragment will be made and connected to the previous one.
51
What direction does the DNA polymerase add the nucleotides on the lagging strand?
3’ end to 5’ end direction
52
What direction does the DNA polymerase add the nucleotides on the leading strand?
3’ to 5’ end
53
How is dna replicates quickly?
To replicate dna quickly they may be many replication forks along the length of the dna.
54
What is the region of replication called?
Replication bubble
55
What is PCR?
Polymerase chain reaction is a method of amplifying a target sequence of DNA.
56
When is PCR used?
In forensics and diagnosis of disease
57
PCR involves three steps which result in what?
Exponential increase in the target sequence of dna
58
What else can PCR be used for?
Analyse extremely small amounts of sample dna.
or analysis of ancient DNA that is tens of thousands of years old
59
What does PCR permit?
Early diagnosis of malignant diseases.
60
What can PCR be able to diagnose?
The presence of aids virus
61
What is needed for PCR?
```
Template dna
Buffer
DNA (Taq) polymerase
Nucleotides
Primers
```
62
What happens to the section of dna which is being amplified in PCR?
Why?
The section of dna must be added to the reaction mixture.
This will act as a template copy.
63
What does the buffer in PCR do?
The buffer keeps the reaction mixture at the correct ph
64
What is the optimum temperature for polymerase enzyme?
Optimum temperature for polymerase enzymes are 37 c
65
What does PCR require polymerase to do?
Why?
Operate at high temperatures.
This means heat-tolerant DNA polymerase must be used
66
What are Taq Polymerase?
An enzyme which adds nucleotides to DNA.
67
Taq Polymerase are a what type of polymerase?
A special type of polymerase which is stable at high temperatures.
68
What is the optimum temperature for Taq polymerase?
Optimum temperature of 70 c
69
What is a primer?
A primer is a strand of DNA which serves as a starting point for polymerase.
70
How are DNA primers designed in the PCR process?
Designed to be complementary to the sequence to amplify a specific are of dna
71
Step 1 of PCR is?
The DNA molecule which is being amplified is first denatured.
It is heated to between 92 and 98 c
This breaks the hydrogen bonds between base pairs.
72
Step 2 of PCR is?
The solution is cooled to between 50 and 65 c to allow the primer to anneal to the single strands of DNA
73
Step 3 of PCR is?
The solution is heated to between 70 and 80 c to allow extension from the primer.
This process is usually repeated at least 30 times.
74
Step 4 of PCR is?
DNA duplex is heat-denatured
Two primers are annealed to the sequence once the solution is cooled
75
Step 5 for PCR is?
Heat-tolerant DNA polymerase then attaches to the primer and copies the templates, doubling the number of copies
76
Polymerase chain reaction allows DNA to be amplified in what?
Vitro
77
In vitro means what?
Out with a living organism
78
What does in vivid mean?
Carried out within an organism like dna replication
79
Once the DNA has been amplified using PCR what can be used next?
Electrophoresis
80
What is gel electrophoresis?
Gel electrophoresis separates macromolecules based on their size and electrical charge.
81
In gel electrophoresis what happens to the DNA fragments?
The dna fragments are stained then loaded into a gel.
82
Once the dna fragments have been loaded into a gel what happens next?
An electric current can be passed through the gel
The dna starts to move through the gel.
83
In gel electrophoresis why does the dna move towards the positive electrodes?
Dna moves towards the positive electrodes because it is negatively charged.
84
What do proteins contain?
Carbon
Hydrogen
Oxygen
Nitrogen
Sometimes sulphur
85
What do proteins consist of?
Chains of amino acids
86
What are amino acids linked by?
Peptide binds to form polypeptides
87
What can a polypeptide consist of?
Hundreds of amino acids linked together
88
How is the order of amino acids in a protein determined?
By the order of bases on the dna strand
89
What do polypeptide chains fold into to form?
Three dimensional shape of a protein
90
The three dimensional shape of a protein is held together by what bond?
Hydrogen bonds and other interactions between individual amino acids
91
A different structure of a protein causes for?
A different function
92
What is the function of an enzyme?
Speeds up the chemical reactions but remain unchanged by the process.
93
Why are enzymes important?
Vitally important to allow chemical reactions to take place at lower temperatures
94
What is the function of an antibody?
They are involved in the body’s immune system, attach onto invading pathogens and signal them for destruction.
95
What is the function hormones?
Chemical messengers which send messages from one part of the body to another.
96
What is the function of a structural protein?
Have a role in support can be found as an important component of the cell membrane as well as a major component of hair, nails and skin
97
What is RNA?
RNA is similar to DNA but has a few key differences
98
What do RNA nucleotides contain?
A ribose sugar
Phosphate
Base
99
RNA uses what as a partner for adenine?
Uracil
100
RNA is a what strand molecule?
Single strand molecule
101
What are the three types of RNA?
Messenger RNA (mRNA)
Transfer RNA (tRNA)
Ribosomal RNA (rRNA)
102
What does mRNA do?
Carries a copy of the code from the DNA in the nucleus to the ribosome in the cytoplasm
103
How is mRNA made?
mRNA is made using code contained in the DNA by a process called transcription
104
What is tRNA?
Carries specific amino acids to the ribosome where they can be linked together in the correct order using the code on the mRNA
105
What is the process tRNA is involved in called?
Translation
106
What is the ribosome?
The site of protein synthesis
107
What is the ribosome made from?
Protein and ribosomal RNA forming a complex
108
What is Transcription?
The first step in protein synthesis
It is when the genetic code on the DNA is used to determine the base sequence on the mRNA
109
Step one of Transcription is?
The dna containing the gene to be transcribed is identified
110
Step two of Transcription is?
RNA polymerase unwinds the DNA and breakdown the hydrogen bonds between the bases causing the strands to separate and expose their bases.
111
Step three of Transcription is?
Free RNA nucleotides find and align with their complementary nucleotide in the open chain by hydrogen bonds
112
step four of Transcription is?
A strong chemical bond forms between the sugar of one RNA nucleotide and the phosphate of the next. Using RNA polymerase.
113
Step five of Transcription is?
This process continues along the length of the gene.
114
Step six of Transcription is?
The weak hydrogen bonds between the DNA and RNA bases break allowing the mRNA to separate from the DNA.
115
Step 7 of Transcription is?
The mRNA moves away from the DNA.
The weak hydrogen bonds between the two dna strands reunite and the molecule winds up into a double helix again.
116
What are the two different segments of genes?
Introns And Exons
117
What are introns?
Introns are non-coding regions of the gene which are removed from the primary mRNA transcript.
118
What are Exons?
Exons are coding regions which are joined together to form a mature mRNA in a process called splicing.
119
What happens to Exons during splicing?
The order of Exons is unchanged during splicing
120
What does nature mRNA only contain?
Exons only
121
What happens to mature mRNA during transcription?
Mature mRNA then moves through pores in the nuclear membrane and carries a copy of the DNA code to the ribosome
122
What is tRNA’s function in translation?
TRNA only exposes one of its triplets this known as the anticodon
123
What does tRNA also have?
An amino acid binding site.
124
What are groups of three bases on mRNA called?
Groups of three bases on MRNA are known as codons.
125
What are the three exposed bases on tRNA?
Anticodons
126
Groups of three bases code for what?
Code for one amino acid
127
What will every protein in translation start with?
Methionine amino acid AUG
128
What are stop codons?
Codons which signal the end of an amino acid.
129
During translation what are the codons on the mRNA used to determine?
Determine sequence of amino acids in the protein.
130
tRNA molecules have what?
Complementary sequences called anticodons
131
tRNA anticodons bases pairs with mRNA why?
tRNA anticodons base pair with mRNA codons temporarily to determine the order of amino acids in the protein
132
Step 1 for translation is?
Each anticodon corresponds to a specific amino acid.
tRNA molecule picks up the appropriate amino acid and aligns it with its corresponding codon on the mRNA at a ribosome.
133
Step two of translation is?
Peptide bonds from between adjacent amino acids
tRNA molecules continue to align their anticodons to the complementary codons on the mRNA.
134
Step three of translation is?
Chain of polypeptide (protein) is released into the cytoplasm
135
What do polypeptide bonds do?
Link amino acids together as the polypeptide chain forms.
136
What happens to the polypeptide chain when completed?
When completed the polypeptide chain is released from the ribosome.
137
What happens when the polypeptide chain is released from the ribosome?
It folds and binds to other polypeptide chains, results in the formation of a mature protein
138
How many times does can tRNA be used?
A tRNA molecule can be used many times to carry its specific amino acid molecule.
139
The mRNA molecule in translation is usually what?
Re-used to produce more identical polypeptide chains.
140
What is a codon?
A codon is a triplet of bases found on mRNA
141
What is an anticodon?
An anticodon is a triplet of bases found on tRNA
142
What is each anticodon specific to?
Each anticodon is specific to one amino acid
143
What do tRNA molecules help determine?
The order of amino acids in the protein which is being produced.
144
What can one gene do?
Give rise to many different types of protein
145
What are the two main processes that allow the production of many proteins from one gene?
Alternative splicing
Post- translational modification
146
What is splicing?
Splicing is the process which joins Exons together to for a mature mRNA.
147
What is alternative splicing?
During alternative splicing different sections of the mRNA transcript are treated as Exons and introns.
148
What happens during alternative splicing?
Many different mature mRNA transcripts are produced from the same primary mRNA transcript.
Therefore may different proteins can be made.
149
What happens after translation?
The polypeptide chain folds to form its final shape and gives its function.
150
What else can happen after translation?
Post-translational modifications may also occur to the polypeptide chain.
151
What is post translational modification?
Changes which take place to the polypeptide chain after translation has taken place.
152
Post translation modification includes what?
Cleavage
| Molecular addition
153
What is cleavage?
Removal of part of a polypeptide chain
154
What is molecular addition?
Adding components to protein
155
What happens in some cases of polypeptide chains?
Sometimes some polypeptide chains may need to be cleaved before the protein will be fully functional.
156
What is an example of a polypeptide chain being cleaved?
Trypsinogen
Trypsin is an enzyme made from trypsinogen which breaks down proteins
157
How is trypsinogen produced?
Produced by transcription and translation of the trypsin gene.
158
Trypsinogen is a what if trypsin?
Inactive form
159
How does trypsinogen become active?
It becomes active trypsin after cleavage if parts of its polypeptide chain
160
What are some examples of molecular addition?
Carbohydrates or phosphate groups
161
What is Mucin?
What does it have?
Mucin is a glycoproteins found in mucus
This protein has a carbohydrate added
162
When will Mucin be fully functional?
Mucin is fully functional when carbohydrate has been added
163
What is another example of molecular addition?
Addition of phosphate
164
What does the enzyme glycogen phosphorylase produce?
Glucose from glycogen
165
How do you turn glycogen phosphorylase active?
It becomes active by the addition of a phosphate
166
What is differentiation?
Differentiation is a process by which unspecialised cells become specialised for a specific function
167
What happens to a zygote in terms of differentiation?
Zygote undergoes differentiation which results in groups of cells that have become specialised to preform different functions.
168
What happens during differentiation?
Many essential genes remain switched on
Some genes for specific characteristics are turned on
Some unnecessary genes are switched off
169
What are some differentiation cells?
```
Muscle cells
Heart cells
Fat cells
Blood cells
Nervous cells
```
170
In animals growth can what?
Occur all over their bodies
171
In plants growth is what?
Restricted to regions called meristems.
172
Where can meristems be found?
Can be found at the tip of the shoot in plants surrounded by young leaves
173
Where else can meristems be found?
Near the end of the roots
174
Near the root of a plant how are meristems protected?
They are protected by a group of cells called the root cap
175
What takes place in the meristem?
What does it produce?
Cell division
Non specialised cells
176
What do non specialised cells in plants have the potential to do?
Become any type of plant cell
177
What does cell division at the meristem allow?
Allows plants to grow
178
What happens to the cells produced at the meristem?
They can differentiate into all the different types of cells found in a plant
179
What are stem cells and where are the found?
What can they do?
Stem cells are unspecialised cells and are found in animals.
They can become any type of body cell
180
What are some examples of cells stem cells can become?
Skins cells
Muscle cells
Blood cells
181
What can stem cells continue to do?
To divide or can differentiate into specialised cells of more or more type.
182
What are the two main types of stem cells?
Embryonic stem cells
Adult stem cells
183
Where are embryonic stem cells found?
Stem cells are found in embryos
184
Where are adult stem cells found?
Found throughout the body
Can be found in children as well as adults
185
What happens in the very early embryo?
Embryonic stem cells differentiate into all the cell types that make up the organism.
186
What happens to tissue stem cells (adult stem cells)?
Tissue stem cells replenish differentiated cells that need to be replaced and give rise to a more limited range of cell types
187
An example of an adult stem cell is?
Hematopoietic stem cells
188
What does stem cell research provide?
Information on how cell processes such as cell growth, differentiation and gene regulation work.
189
What type of stem cells are being sued in stem cell research right now?
Mice or human stem cells
190
Adult stem cells that are used in medicine?
Bone marrow
Skin
Heart muscle
Bladder
191
What is the use of bone marrow stem cells?
Can develop into all the types of cell found in blood and can be used to treat leukaemia a cancer caused by abnormal blood cells.
192
Use of skin cells are?
Growing a new layer of skin which can be used to treat burn victims.
193
What is the use of heart muscles cells?
Repairing damaged heart muscle after a heart attack
194
Use of bladder stem cells are?
Building a new bladder in lab for a patient whose bladder has been damaged by injury or disease.
195
What is believed of stem cells?
Stem cells could be directed to differentiate into any type of cell and replace damaged or diseased ones.
196
What do stem cells have the potential to cure?
Potential to cure Parkinson’s disease, Alzheimer’s disease, MS or cardiac disease
197
What are the ethical issues surrounding stem cell research and medicine?
The distraction of embryos
The development of techniques which are similar to cloning
198
What are the laws that keep stem cell research tightly regulated?
Human fertilisation and embryology act and human reproductive cloning act.
199
Why are stem cell regulations put in place?
To ensure that all practices involving stem cells are ethical
200
What is a genome?
A genome of an organism is its entire hereditary information encoded in its DNA
201
How is the entire hereditary information organised in humans?
It is organised into 46 chromosomes
202
What is genome made up of?
A genome is made up of genes which carry instructions for making all the proteins and other DNA sequences that do not code for proteins.
203
What does a genome contain?
Coding and non-coding sequences
204
What do most eukaryotic genomes consist of?
Non coding sequences
205
What are the several functions of non-coding sequences in genomes?
Regulations transcription
Transcription of RNA
No known function
206
What are the non-coding sections of dna which are use to regulate transcription do?
They can bind proteins which promote or prevent transcription of a gene
207
What do some sections of DNA do?
Get transcribed into RNA but not translated
208
What are the three types of RNA that are not translated into proteins?
tRNA
rRNA
Non-translated forms of RNA
209
What are RNA fragments?
rNA fragments are small sections that are not translated which are involved in splicing and other processes such as post transcriptional regulation of genes.
210
large sections of the genome are still what?
Large sections of the genome are still unknown
211
What is a mutation?
Mutations are changes in the dna that can result in no protein or an altered protein being synthesised.
212
Mutations occur when?
Mutations are spontaneous and usually randomly occurs and at low frequencies
213
What can mutations affect?
May affect just one base of an organisms DNA or could affect the structure or number of whole chromosomes.
214
When is an individual know as a mutant?
When the change in the genotype affects the phenotype of an organism
215
What are some examples of mutagenic agents?
Radiation and chemicals
216
Examples of radiation that causes mutations?
UV radiation, x-rays and gamma rays
217
Examples of chemicals that cause radiation?
Bromine
Mustard gas
Nicotine
Tar
218
What is a single gene mutation?
Single gene mutations involve the alteration of a DNA nucleotide sequence as a result of the:
Substitution
Insertion
Deletion
Of a nucleotide
219
In order for a protein to work properly what must happen?
The protein must have the correct order of amino acids which is determined by the DNA base sequence
220
What is a substitution mutation?
A substitution mutation means one base is substituted for another and a wrong amino acid may be inserted into a protein
Usually these changes are minor but they can cause major problems in some cases I.e sickle cell anaemia
221
What is an insertion mutations?
Insertion means a certain number of nucleotides are inserted into a DNA molecule and all the subsequent triplets are read incorrectly
The protein which is made will therefore probably have many different amino acids and may not work at all.
222
What is a deletion mutation?
A deletion mutation means a certain number of nucleotides are removed from the DNA molecule and all the subsequent triplets are read incorrectly.
The protein which is made will therefore probably have many different amino acids and may not work at all.
223
What does a protein require?
It requires the correct sequence of amino acids to function correctly.
224
What happens if the base of a gene is disrupted?
If the base of a gene is disrupted the amino acid sequence may be disrupted as well
225
What are the effects of a substitution mutation?
Missense
Nonsense
Splice site mutation
226
What is a missense?
Results in one amino acids being changed for another.
This may results in a non-functional protein or have little effect on the protein.
227
What is a nonsense?
A nonsense mutation results in a premature stop codon being produced which results in a shorter protein
228
What is a splice site mutation?
Splice site mutations result in some introns being retained and/ or some Exons not being included in the mature transcript.
229
What do splice site mutations alter?
It alters post-transcriptional processing
230
What effects do nucleotide insertion and deletion mutations result in?
They result in frame-shift mutations which usually have greater effects than substitutions, especially if 1 or 2 bases are inserted or deleted
231
What do frame-shift mutations do to mRNA codons?
They cause all of the codons and all of the amino acids after the mutation to be changed. This has a major effect on the structure of the protein produced.
232
What do mutations bring source to?
New variation in living things
233
What do mutations create?
New alleles
234
What do new alleles give rise to?
Give rise to variation with a population
235
What does variation within a population make possible?
Makes it possible for a population to revolve over time in response to change environmental conditions.
236
How do mutations in chromosomes happen?
When one of more chromosomes breaks
237
What are the broken ends of a mutated chromosome described as?
Broken ends are sticky and can join to another broken end
238
What do changes in chromosomes structure involve?
They involve the number or sequence of genes on a chromosome being altered
239
What are the four types of chromosome changes?
Duplication
Deletion
Inversion
Translocation
240
What is a duplication chromosomal mutation?
Where a section of a chromosome is added from its homologous partner.
241
How does a duplication chromosomal mutation work?
A segment of genes that may have been deleted from its homologous partner, becomes attached to one end of the chromosome or becomes inserted somewhere along its length.
242
What can a duplication chromosomal mutation occasionally result in?
Can occasionally result in the duplication of an entire gene
243
If an entire gene is duplicated what can happen to it?
The second copy of the gene is free from selection pressures which allows it to undergo point mutations that produce new DNA sequences without affecting the function of the original gene.
244
What is the gene mutation thought to be important?
Gene duplication is thought to be an important driving force in evolution
245
What is a deletion chromosomal mutation?
This is where a chromosome breaks in two places and the segment in between becomes detached. The two remaining ends then join up which results in a shorter chromosome which lacks certain genes.
246
What effect does deletion chromosomal mutations have?
They normally have drastic effects on the organisms involved
247
What is an inversion chromosomal mutation?
Inversion is where a section of chromosomes is reversed
This is where a chromosome breaks in two place releasing a section which turns around then joins back up again. This reverses the normal sequence of genes in the affected section of chromosome.
248
What is translocation?
Where a section of a chromosome is added to a chromosome that is not its homologous partner
249
What are the two types of translocation?
Reciprocal translocation
Non-reciprocal translocation
250
What is reciprocal translocation?
It occurs when chromosomal segments are exchanged between two non-homologous chromosomes and is the most typical type of translocation.
251
What is non-reciprocal translocation?
A one-way transfer of a chromosomal segment to another chromosome
252
What is evolution?
Evolution is the changes in organisms over generation as result of genomic variations.
253
What is the key process in evolution?
Inheritance
254
What are the two main ways of transferring genetic material from one organism to another?
Vertical gene transfer
Horizontal gene transfer
255
What is vertical gene transfer?
Where genes are transferred from a parent to offspring
256
What type of organism does vertical gene transfer occur in?
Eukaryotes and prokaryotes
257
What is vertical gene transfer resulted from?
Sexual or asexual reproduction
258
What happens in sexual reproduction in terms of gene transfer?
Genetically diverse parents produce offspring showing genetic variation
259
What happens in asexual reproduction in terms of gene transfer?
A single parent produces offspring with the same genome
260
What is horizontal gene transfer?
Where genes are transferred between individuals in the same generation
261
What is horizontal gene transfer resulted from?
It occurs from prokaryotes
262
What does horizontal gene transfer result?
Faster evolutionary changes than in organism that only use vertical transfer as it allows new genetic sequences to be transferred between prokaryotes very quickly.
Allowing rapid evolution of prokaryotes
263
Why is horizontal gene transfer risky?
It’s risky strategy as they are no guarantees the transferred genetic material will give an advantage
264
What does genetic transfer between species do?
It may confer some advantages
265
What happens once a sequence is transferred horizontally?
It may be passed on vertically to the next generation
266
What can eukaryotes not do in reference to gene transfer?
Carry out horizontal inheritance
However they can revive horizontally from bacteria and viruses
267
What is natural selection?
Natural selection is the one non-random increase in frequency of DNA sequences that increase survival and the non-random reduction in frequency of deleterious DNA sequences.
268
What does natural selection eliminates?
It eliminates less well adapted organisms, usually preventing their growth or killing them.
269
What happens to certain characteristics during natural selection?
The become more or less common in a population due to factors within the environment
270
Step one of natural selection is?
Mutations change genotypes which leads to phenotype changes
271
Step two of natural selection is?
Natural selection pressures acts on phenotypes
272
Step three of natural selection is?
Extinction of organisms with phenotypes which have reduced selective advantage
273
Step four of natural selection is?
Competition leads to survival or organisms with phenotypes with selective advantages
274
Step five of natural selection is?
Breeding leads to increase in frequency of mutations which gave selective advantage
275
What can cause the change in phenotype frequency?
Stabilising selection
Directional selection
Disruptive selection
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What is stabilising selection?
In stabilising selection the average phenotype is selected for and the extreme of the phenotype range are selected against
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What is directional selection?
In directional selection one extreme of the phenotype range is selected for?
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What is disruptive selection?
In disruptive selection two or more phenotypes are selected for
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What is a species?
A group of organism capable of interbreeding and producing fertile offspring and which does not normally breed with other groups
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What is speciation?
The generation of new biological species by evolution as a result of isolation mutations and selection.
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How does a species remain one species?
As long as a population has the opportunity to interbreed and exchange genes, they remain one species
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How does a population of one species revolve into more then one?
It evolves into more then one species if groups within the population become isolated by barriers that prevent exchange of genes
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What are the three main stages of speciation?
Isolation by a barrier
Mutations
Natural selection
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Stages speciation are?
Step 1
One species exists which interbreeds and shares the same gene pool
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Step two of speciation is?
Isolation
The population becomes isolated by a barrier into two sub-populations, this means they no longer interbreed
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Step three of speciation is?
Mutations
Mutations occur at random, different mutations occur in each of the sub-populations causing new variation
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Step four for speciation is?
Natural selection
Natural selection acts on each sub-group in a different way due to different selection pressures
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Once the steps of speciation happens what happens next?
Over a long period of time the gene pools in the two sub populations become so altered that the groups cannot interbreed
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What happens if the isolation barrier is removed?
The population cannot interbreed therefore speciation has occurred
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What are the two types of speciation?
Allopatric speciation
| Sympatric speciation
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What is allopatric speciation?
The gene flow between two or more populations is prevented by a geographical barrier.
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What are geographical barriers?
What are some examples of geographical barriers?
Physical barriers on earth
River
Mountains
Deserts
Sea/ocean
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Step one of allopatric speciation is?
Large interbreeding population
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Step two of allopatric speciation is?
Isolation of population
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Step three of allopatric speciation is?
Separate populations mutate randomly giving rise to new variation
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Step four of allopatric speciation is?
Natural selection favours mutants
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Step five of allopatric speciation is?
Over a long period of time natural selection increases frequency of new alleles
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Step six of allopatric speciation is?
Speciation has occurred
Species A and B cannot interbreed even if barrier is removed
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What is sympatric speciation?
The population live in close proximity in the same environment but still become genetically isolated
Sympatric speciation is the evolution of new species in populations that live in the same geographic area
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What are two barriers in sympatric speciation?
Behavioural and ecological
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What is a ecological barrier?
Is a barrier that is caused by changes in abiotic factors and food availability
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What is a behavioural barrier?
Barrier which is caused by populations becoming sexually receptive at different times of the year or having different breeding patterns or rituals
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Step one of sympatric speciation is?
Large interbreeding population sharing the same ecological niche
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Step two of sympatric speciation is?
Alternative ecological niche spears. Some members of the population start to exploit the new niche
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Step three of sympatric speciation is?
Two populations now exploit different resources and no longer interbreed.
Behaviour has become an isolation barrier
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Step four of sympatric speciation is?
Mutants better adapted to exploit the new resources appear and successfully breed
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Step five of sympatric speciation is?
Natural selection favours the new mutants and eventually over a period of time two genetically distinct species are formed which can no longer interbreed.
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What is a genome?
A complete set of genetic material is a genome
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What is genomics?
The study of genomes and involves sequencing an organisms DNA
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To study the genome what must be found out?
The order of the bases along the entire length of an organisms DNA
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What must scientists first determine before studying genomics?
The entire DNA sequence of the organism being studied
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What can the entire DNA sequence of an organism be used for?
Sequence an individual gene or whole genome
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How is the DNA sequence analysed?
The information of the order of bases is analysed using computer technology and statistical analysis
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What is bioinformatics?
The fusion of molecular biology with computer technology and statistical analysis
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What does bioinformatics allow an organism to do?
Allows an organisms genome to be mapped and the information analysed very quickly
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What can the information contained within the genome be used to discover?
Evolutionary relationships
Patterns of inheritance
Personalised medicine
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What are the examples of genomics being able to determine the genome of a range of organisms?
Disease causing organisms
Pest species
Species that are important model organisms
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What is an example of a disease causing organism?
Pathogens- bacteria or viruses
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What is any example of pest species?
Mosquitoes
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What does it mean by a species that are important model organisms?
An organism that posses genes equivalent to human genes and can be easily studied in a lab
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Step one of genomic sequencing is?
A restriction endonuclease (restriction enzyme) is an enzyme that recognises specific short sequences of DNA nucleotides called restriction sites.
These enzymes will then ‘cut’ the DNA at every point where these sequences appear
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Step two of genomic sequencing is?
A portion of dna with an unknown base sequence is chosen to be sequenced
Many copies of this DNA’s strand are synthesised using PCR.
In order to make dna strands that are complementary to these template strands, all the ingredients needed for synthesis are added to the preparation.
DNA polymerase, primer and four types of DNA nucleotides.
In addition the preparation receives a supply of modified nucleotides each tagged with different fluorescent dye
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What is section two of step two of genomic sequencing?
Every so often during the synthesis process a molecule of modified nucleotides just happens to be take up instead of a normal one.
When a modified nucleotide is incorporated into the new dna strand it brings the synthesis of that strand to a halt because a modified nucleotide does not allow a subsequent nucleotide to become bonded to it.
Provided that the process is carried out on a large enough scale the synthesis of a complementary strand will have been stopped at every possible nucleotide position on the DNA template
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Step three of genomic sequencing is?
The mixture of dna fragments of various lengths is separated using electrophoresis. In this process the smallest fragment travel the furthest distance.
Identity and sequencing of nucleotides as indicated by the fluorescent dyes, is then read for the complementary DNA using this separation.
From this information, the sequence of the bases in the original DNA can be deduced
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Step four in genomic sequencing is?
Process has been automated by linking the detection of the four fluorescent dyes to a computer. As those are monitored, the computer working as an automated sequencing analyser process les the information and rapidly displays the sequence of bases in the dna sample as a series of peaks
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What is the genome shotgun approach?
Once the sequence has been determined the pieces have to be put back together.
This is done by computer analysis of the sequences looking for sections that over-lap
Computer analyses all areas of overlap between dna fragments in a sample and is able to compile a complete genome based in these overlaps
Die to fragments all having DNA sequenced this procedure enables scientists to determine the sequence of bases for individual genes and for entire genomes.
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What does comparative genomics compare the sequenced genome of?
Members of the same species
Members of different species
Cancerous versus normal cells
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What does comparing genomes of members of the same species allow?
Allows scientists to discover which genetic sequences cause illness
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What does comparing genomes of members of the different species allow?
Whether they have important genetic sequences in common
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What does comparing genomes of members of cancerous cells v non-cancerous cells of the same individual allows?
Scientists to investigate the specific ‘driver’ mutation that causes a healthy cell to divide uncontrollably and form a tumour
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What happened when scientists compared genomes from different species?
They noted that many parts of the genome are highly conserved
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What does concerned mean?
Identical or almost identical
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Why are the concerned regions of dna useful?
They are useful in determining evolutionary relationships. The greater the number of conserved DNA sequences species have in common the more closely related they are
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What is an SNP?
An SNP is a single nucleotide polymorphism. Cause by a variation in DNA sequence that affects a single base pair in a dna chain.
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What do SNP’s do?
They are one of the way in which genomes are found to differ from one another
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The use of bioinformatics helps with SNP’s how?
It has enabled scientists to catalogue more than a million SNP’s and and specify their exact locations in human genome.
Believing that the SNP map will help them identify and understand the workings of genes associated with disease
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What are SNP’s regarded as and what can the aid with?
They are regarded as valuable tool in research
May aid in the development of future treatment for genetic disorders
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What is polygenetics?
The study of evolutionary history and relationships
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What does polygenetics use?
Genome sequence data to deduce evolutionary relationships which indicate how closely related different species are
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What would the sequence of closely related species look like?
Closely related species are found to have very similar genomes in the sequence of their nucleotide bases.
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What would the sequence of distantly related species look like?
They are found to have genomes that are less similar in the sequence of their nucleotide bases
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What is a phylogenetic tree?
A diagram that shows the evolutionary relationships
The closer two species are on the tree the more closely related they are to each other
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What is sequence divergence?
A group of closely related living things acquire its own set of mutations which gradually alter their genome
If group gives rise to two groups they become more and more different from one another and eventually diverge.
Changes occur in each groups genome that are distinct from those occurring in the groups genome
The more different the base sequenced two genomes the more distantly related the two group must be.
This information can be used to estimate the time since the groups diverged
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What does it mean if you can trace a common ancestor of two species relatively recently?
This means the species diverged recently and can be described as closely related
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What can infer with evolutionary relatedness?
Can be inferred by the number of changes to the genome when comparing the two species
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What are molecular clocks?
Are used to show when species diverged during evolution
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What do molecular clocks assume?
A constant mutation rate and show difference in DNA sequence or amino acid sequences
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What does the difference In sequence data between species indicate?
Indicates the time of divergence from common ancestor
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The comparison of rRNA sequence provides evidence of three domains of life
What are they?
Bacteria- traditional prokaryote
Archaea- most prokaryotes that inhabit extreme environments such as hot spring and salt lakes
Eukaryotes- animal, plants, fungi
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What does personalised genomics involve?
What can the information predict?
Sequencing individuals genome and analysis if it using bioinformatic tools
The likelihood of developing certain diseases
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What is the ultimate goal of personalised genomics?
What does this mean?
Produce personalised medicine (pharmacogenetics)
It means giving patients drugs which suit their exact metabolism based on their genomics
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Pharmacogenetics refer to what?
Genetic differences in metabolic pathways which can affect individual responses to drugs
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What is hoped analysing a persons genome will do?
Most suitable drug and the correct dosage can be prescribed
This would increase the success of treatment and reduce any side effects
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What is hoped pharmacogenetics will do in the future?
Help inform someone if their genetic predisposition of any sort of disease
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What are the ethical issues for pharmacogenetics?
The main issue is who has the right to see the information
