Mutations And Gene Expression Flashcards
What are the 2 types of gene that control gene division and what do they do?
Tumour suppressor genes and proto-oncogenes
TSG- slow cell division by producing proteins that stop cells dividing or cause them to self-destruct
Proto-oncogenes- Stimulate cell division by producing cells that make cells divide
What will happen to TSG if there is a mutation in the DNA sequence
Inactivated.
The protein that stops cell division/ makes cells self-destruct, isn’t produced so cells divide uncontrollably so tumour
What will happen to proto-oncogene if a mutation occurs in the DNA sequence?
Produces a mutated proto-oncogene called an oncogene
If a mutation occurs, this may result in an overactive gene which stimulates the cells to divide uncontrollably so tumour forms.
Identify and describe BAD tumours
Malignant tumours are cancers.
Usually grow rapidly, invade and destroy surrounding tissue’s.
Cells can break off the tumour and spread to other areas of the body via bloodstream or lymphatic system
Describe HARMLESS tumours :
Benign cancers aren’t cancerous. Usually gore slower than M and are often covered in fibrous tissue that stops cells invading other tissue’s.
Often harmless but cause blockages and out pressure on organs.
Can become malignant.
How are tumours different to normal cells?
- irregular shape
- nucleus is larger and darker
- different antigens on their surface
- Don’t respond to growth regulating processes
- divide by mitosis more frequently
Oestrogen is a substance produced by the enzyme aromatase. In females, the main source of oestrogen is the ovaries but aromatase is produced by many other organs in the body, including the lungs. Oestrogen can stimulate the development of some lung tumours. In these tumours, binding of oestrogen to cell-surface receptors stimulates cell division.
Scientists investigated whether two drugs could prevent lung tumours in female mice. First, they removed the ovaries from these mice. They then injected the mice with a tumour-causing chemical found in tobacco twice a day for 4 weeks. The mice were then randomly allocated to one of four groups. Each group contained 10 mice.
- Group Q was given a placebo. This placebo did not contain either drug.
- Group R was given the drug anastrozole. This inhibits the enzyme aromatase.
- Group S was given the drug fulvestrant. This binds to oestrogen receptors.
- Group T was given both anastrozole and fulvestrant.
The mice were given these drugs each week during weeks 5−15 of the investigation.
(a) The scientists removed the ovaries from the mice for the investigation. They also gave the mice injections of the substrate of aromatase each day.
Explain why these steps were necessary.
Removes (main / largest) source of oestrogen / (different) mice produce different amounts of oestrogen
(Allows) oestrogen to be controlled / oestrogen to be made by aromatase only / only oestrogen made in lungs to be involved.
Oestrogen is a substance produced by the enzyme aromatase. In females, the main source of oestrogen is the ovaries but aromatase is produced by many other organs in the body, including the lungs. Oestrogen can stimulate the development of some lung tumours. In these tumours, binding of oestrogen to cell-surface receptors stimulates cell division.
Scientists investigated whether two drugs could prevent lung tumours in female mice. First, they removed the ovaries from these mice. They then injected the mice with a tumour-causing chemical found in tobacco twice a day for 4 weeks. The mice were then randomly allocated to one of four groups. Each group contained 10 mice.
- Group Q was given a placebo. This placebo did not contain either drug.
- Group R was given the drug anastrozole. This inhibits the enzyme aromatase.
- Group S was given the drug fulvestrant. This binds to oestrogen receptors.
- Group T was given both anastrozole and fulvestrant.
The mice were given these drugs each week during weeks 5−15 of the investigation.
The scientists predicted that fulvestrant would be more effective when given with anastrozole than when given alone.
Use the information provided to suggest why they predicted this.
- (Anastrozole) prevents / reduces oestrogen production;
2. (Fulvestrant) stops remaining oestrogen binding / less oestrogen binds to receptors.
The scientists used tumour area as an indicator of tumour size.
Explain why tumour area may not be the best indicator of tumour size and suggest a more reliable measurement.
- Tumours may be different depths / area does not take depth into account / tumours are 3-D / are not 2-D
- Should (Measure) tumour volume / mass / weight.
The scientists repeated the investigation but this time they did not give the drugs until week 9.
Suggest why they gave the drugs at week 9, rather than at week 5.
- Allows tumours to grow / develop / form;
Neutral: gives drug more time to work.
- (So) can investigate treatment rather than prevention (of tumours) / when tumour / cancer is more advanced
Another group of scientists is currently using these drugs in human trials. However, the control group is not being given a placebo.
Suggest why a placebo is not being given and what is being given to this group instead.
- Unethical (not to treat patients) / may increase probability of patients dying / getting more ill;
- Use normal cancer drugs / treatment.
A mutation of a tumour suppressor gene can result in the formation of a tumour.
Explain how.
- (Tumour suppressor) gene inactivated / not able to control / slow down cell division;
Ignore: references to growth
- Rate of cell division too fast / out of control.
Not all mutations result in a change to the amino acid sequence of the encoded polypeptide.
Explain why.
- (Genetic) code degenerate;
2. Mutation in intron.
Some cancer cells have a receptor protein in their cell-surface membrane that binds
to a hormone called growth factor. This stimulates the cancer cells to divide.
Scientists have produced a monoclonal antibody that stops this stimulation.
Use your knowledge of monoclonal antibodies to suggest how this antibody stops the growth of a tumour.
- Antibody has specific tertiary structure
- Complementary (shape / fit) to receptor protein / GF
- Prevents GF binding (to receptor).
Explain how the methylation of tumour suppressor genes can lead to cancer.
- Methylation prevents transcription of gene;
- Protein not produced that prevents cell division / causes cell death / apoptosis;
- No control of mitosis.
The doctors compared median survival times for patients in each group.
How would you find the median survival time for a group of patients?
- Rank all STs (survival times) in ascending order;
2. Find value with same number (of people) above and below.
In many trials of new drugs, a control group of patients is given a placebo that does not contain any drug.
The control group in this investigation had been treated with dacarbazine. Suggest why they had not been given a placebo.
Not ethical to fail to treat cancer.
MM is caused by a faulty receptor protein in cell-surface membranes. Cells in MM tumours can be destroyed by the immune system.
Suggest why they can be destroyed by the immune system.
- Faulty protein recognised as an antigen / as a ‘foreign’ protein;
- T cells will bind to faulty protein / to (this) ‘foreign’ protein;
- (Sensitised) T cells will stimulate clonal selection of B cells;
- (Resulting in) release of antibodies against faulty protein.
Alzheimer’s disease (AD) is a non-reversi
number of years. At the start of 2014 the number of Americans with AD was
estimated to be 5.4 million. Every 30 seconds another person in America
develops AD.
5 In the brain of a person with AD there is a lower concentration of acetylcholine.
This affects communication between nerve cells and initially results in memory
loss and confusion. Some of the symptoms of AD that are associated with
communication between nerve cells are reduced by taking the drug donepezil.
Donepezil inhibits the enzyme acetylcholinesterase.
10 A gene mutation called E280A found on chromosome 14 causes early-onset AD
at a mean age of 49 years. The age at which the E280A mutation is expressed
to cause AD varies.
Yaramul is a town in a historically isolated region of the Andes Mountains. The
population of this town has the highest frequency of the E280A mutation in the
15 world. The origin of the E280A mutation in this population has been traced back
to a common ancestor in the 17th century. Natural selection has not reduced
the frequency of the E280A mutation in the population.
This autosomal dominant mutation involves a change in triplet 280 from GAA to
GCA. Scientists analysed chromosome 14 from 102 individuals from Yaramul.
20 They recorded a sample size of 204 and detected 75 E280A mutations but only
74 potential AD cases. The scientists identified individuals with the mutation by
whole genome sequencing. They had decided that a DNA probe would not be a
suitable method to detect the E280A mutation.
(a) Assuming no one with AD died in 2014, calculate the annual percentage increase in AD cases in America for 2014 (lines 2–4).
Correct answer of 19.4 / 19.41%
OR
19.47 / 19.5% = 2 marks;
“loss and confusion. Some of the symptoms of AD that are associated with
communication between nerve cells are reduced by taking the drug donepezil.
Donepezil inhibits the enzyme acetylcholinesterase.”
Explain how donepezil could improve communication between nerve cells (lines 7–9).
- Less / no acetylcholine broken down;
- Acetylcholine attaches to receptors;
- (More) Na+ enter to reach threshold / for depolarisation / action potential / impuls
“Yaramul is a town in a historically isolated region of the Andes Mountains. The
population of this town has the highest frequency of the E280A mutation in the
15 world. The origin of the E280A mutation in this population has been traced back”
Suggest and explain two reasons why there is a high frequency of the E280A mutation in Yaramul
- Isolated so inbreeding / low genetic diversity / small gene pool;
- Allele inherited (through generations) from (common) ancestor
“to a common ancestor in the 17th century. Natural selection has not reduced
the frequency of the E280A mutation in the population.”
Explain why natural selection has not reduced the frequency of the E280A mutation in the population
- AD / symptoms develops late / at 49;
2. Have already reproduced
“at a mean age of 49 years. The age at which the E280A mutation is expressed
to cause AD varies.”
The age at which the E280A mutation is expressed to cause AD can vary (lines 11–12).
Suggest and explain one reason for this.
- Epigenetics / environment / named factor e.g. stress, alcohol, toxins, diet, exercise, smoking;
- methylation (of genes)
OR
acetylation (of histones)
One scientific study which analysed chromosome 14 involved 102 individuals. The scientists recorded a sample size of 204. In this sample they detected 75 E280A mutations but only 74 potential AD cases (lines 19–21).
Suggest explanations for the figures the scientists recorded.
- One person was homozygous dominant / has two dominant alleles = 2 marks;
- For one mark has two alleles / chromosomes
“whole genome sequencing. They had decided that a DNA probe would not be a
suitable method to detect the E280A mutation”
Suggest why a DNA probe for the mutated triplet was not considered a suitable method for detection of the E280A mutation
- (GCA / triplet) is common / found in other places;
- Would not know if it was the mutation / allele / gene
OR
Produces ‘false positives’
Scientists have investigated the use of different types of stem cell to treat damage to the heart after a myocardial infarction. During a myocardial infarction, a number of different cell types in the heart die. This includes cardiomyocytes which are heart-muscle cells.
Embryonic pluripotent stem cells (ESCs) can divide and differentiate into a wide range of different cell types.
(a) Using the information given, suggest one reason why ESCs might be suitable to treat damage to the heart.
(ESCs) can replace any type of (heart) cell;
ESCs have not yet been used to treat people who have had a myocardial infarction. This is because of concern that the use of ESCs might lead to more harm to the person. One way that ESCs might lead to more harm is by differentiating into the wrong types of cells.
Suggest one other way that putting ESCs into a person’s heart might lead to more harm to the person.
- Might divide out of control;
2. Leading to tumour / cance
Suggest how the growth of new blood vessels into damaged heart tissues could increase the rate of repair of tissues.
- Greater blood supply (to damaged areas);
- Bringing more oxygen / glucose for respiration;
- Brings more amino acids for protein synthesis;
- For cell repair / mitosis / division
The scientists used an optical microscope to measure the number of capillaries in thin sections cut from samples of heart muscle.
Describe the method they would have used to find the mean number of capillaries per mm2.
- Measure diameter of field of view and calculate area;
- Using micrometer slide and eyepiece graticule;
Accept descriptions
- Count number of capillaries in large number of fields of view and calculate mean;
- Select fields of view randomly
“Plants require phosphate ions that they get from soil. These ions are often in poor supply and this results in poor growth of the plants.”
Suggest and explain two reasons why a poor supply of phosphate ions results in poor growth of plants
- (Required to) make ATP / glucose phosphate, so less respiration / less energy for growth;
- (Required to) make nucleotides, so less DNA / mRNA / tRNA for cell division / production of protein (for growth);
- (Required to) make RuBP / NADP, so less CO2 fixed / reduced into sugar;
- (Required to) make phospholipids for membrane
“Plants can defend themselves by producing defensive enzymes that destroy pathogens such as bacteria.”
Suggest how defensive enzymes produced by plants destroy bacteria
- Hydrolyse;
Accept digest
- murein / glycoprotein (in cell wall);
“Some plants express the genes for defensive enzymes in response to signal proteins secreted by other plants that are being attacked by a pathogen. These signal proteins can be released into the air.”
The signal proteins secreted into the air by a plant being attacked by a pathogen act as stimuli leading to the expression of genes for defensive enzymes in other plants (lines 9–12).
Suggest how they lead to the expression of these genes
- Bind to receptor (on target plant);
- Acts as / leads to production of a transcription factor;
- (Which) binds to promoter
“Some plants express the genes for defensive enzymes in response to signal proteins secreted by other plants that are being attacked by a pathogen. These signal proteins can be released into the air.”
“Scientists have discovered that tomato plants increase production of defensive enzymes if plants next to them become infected with a pathogen. These tomato plants were connected by a mycorrhizal network that can carry signal proteins between them.”
Suggest and explain the advantage to tomato plants of transmitting signal proteins through mycorrhizal networks, rather than releasing them into the air (
Direct plant-to-plant transmission;
- (So) localised response
OR
faster response
Define what is meant by epigenetics.
- Heritable changes in gene function;
2. Without changes to the base sequence of DNA;
Does oestrogen bind to DNA? PROTEIN?
Do methyl groups bind to DNA? PROTEIN?
Do acetyl groups bind to DNA?PROTEIN?
Oestrogen- protein
Methyl- DNA
Acetyl- protein
Explain how increased methylation could lead to cancer.
- Methyl groups (could be) added to (both copies of) a tumour suppressor gene;
- The transcription of tumour suppressor genes is inhibited;
- Leading to uncontrolled cell division
Give one way in which benign tumours differ from malignant tumours.
Cells of benign tumours cannot spread to other parts of the body / metastasise;
OR
Cells of benign tumours cannot invade neighbouring tissues.
What does degenerate mean?
More than one codon codes for a single amino acid
) HIV attaches to a specific protein receptor on helper T cells. A low percentage of people have a mutation of the CCR5 gene which codes for this protein receptor. This mutation results in a non-functional protein receptor.
Explain how this mutation can result in the production of a non-functional protein receptor.
- Change in DNA base/nucleotide (sequence);
Accept: mutation in DNA base (sequence).
Accept: deletion/substitution/addition of a DNA base/nucleotide. - Change in amino acid (sequence)/primary structure;
Reject: different amino acid formed.
Ignore: change in code for amino acid. - Alters (position of) hydrogen/ionic/disulfide bonds;
- Change in tertiary structure (of receptor);
Explain what is meant by an allele
different form of a gene;
Explain how DNA replicates.
hydrogen bonds broken;
semi-conservative replication / both strands used (as templates);
nucleotides line up complementary / specific base pairing / A and T / C and G;
DNA polymerase
Explain why a mutation involving the deletion of a base may have a greater effect than one involving substitution of one base for another.
) deletion causes frame shift / alters base sequence (from point of mutation);
changes many amino acids / sequence of amino acids (from this point);
substitution alters one codon / triplet / one amino acid altered / code
degenerate / same amino acid coded for;
Lysozyme is an enzyme consisting of a single polypeptide chain of 129 amino acids.
(a) What is the minimum number of nucleotide bases needed to code for this enzyme?
387
Give two factors which might increase the frequency at which a mutation in DNA occurs.
) high energy radiation / X rays / ultraviolet light / gamma rays;
high energy particles / alpha particles / beta particles;
named chemical mutagens e.g. benzene / caffeine / pesticide /
mustard gas / tobacco tar / free radicals;
(two named examples of any of the above = 2 marks)
length of time of exposure (to a mutagen);
dosage (of mutagen);
Give two characteristic features of stem cells
Will replace themselves / keep dividing / replicate;
Undifferentiated / can differentiate / develop into other cells / totipotent / multipotent / pluripotent;
The doctors mixed the stem cells with viruses. The viruses had been genetically modified to contain alleles of a gene producing full immunity. The doctors then injected this mixture into the child’s bone marrow.
The viruses that the doctors used had RNA as their genetic material. When these viruses infect cells, they pass their RNA and two viral enzymes into the host cells.
(b) One of the viral enzymes makes a DNA copy of the virus RNA. Name this enzyme.
Reverse transcriptase
The other viral enzyme is called integrase. Integrase inserts the DNA copy anywhere in the DNA of the host cell. It may even insert the DNA copy in one of the host cell’s genes.
(c) (i) The insertion of the DNA copy in one of the host cell’s genes may cause the cell to make a non-functional protein. Explain how
) Alters base / nucleotide sequence / causes frame shift;
Different sequence of amino acids in polypeptide / protein / primary structure alters the tertiary structure
Some of the children in the trial developed cancer. How might the insertion of the DNA have caused cancer?
) Affects tumour suppressor gene;
Inactivates (tumour suppressor) gene;
Rate of cell division increased / tumour cells continue to divide
Transcriptional factors are important in the synthesis of particular proteins.
Describe how.
- Bind to DNA/gene;
- At specific region/base sequence/promoter sequence;
- Stimulate transcription / prevents transcription / turn on gene / turn off gene
The siRNA-protein complex attaches to an mRNA molecule coding for a particular protein (step 2). Explain what causes the siRNA to attach only to one sort of mRNA molecule.
Has complementary base sequence
Describe and explain how expression of the target gene is affected by siRNA
- No longer able to make specific protein / cannot make
whole protein / mRNA cannot be translated; - Because mRNA has been cut into pieces;
Oestrogen is a hormone that affects transcription. It forms a complex with a receptor in the cytoplasm of target cells. Explain how an activated oestrogen receptor affects the target cell
) (Receptor/transcription factor) binds to promoter;
Stimulates RNA polymerase/enzyme X;
Transcribes gene/increase transcription
Oestrogen only affects target cells. Explain why oestrogen does not affect other cells in the body
Similar shape to oestrogen;
Binds receptor/prevents oestrogen binding;
Receptor not activated/will not attach to promoter/no transcription
A mutation in the base sequence of the DNA that codes for the toxin would change the base sequence of the mRNA.
Explain how a change in the base sequence of the mRNA could lead to a change in the tertiary structure of the toxin.
…………………………………………………………………………………………………………
) Different primary structure / amino acid sequence / amino acid coded for
The black mamba’s toxin kills prey by preventing their breathing. It does this by inhibiting the enzyme acetylcholinesterase at neuromuscular junctions. Explain how this prevents breathing.
) 1. Acetylcholine not broken down / stays bound to receptor;
- Na+ ions (continue to) enter / (continued) depolarisation / Na+ channels
(kept) open / action potentials / impulses fired (continuously); - (Intercostal) muscles stay contracted / cannot relax;
What name is used for the non-coding sections of a gene?
introns
Gene mutations occur spontaneously.
(i) During which part of the cell cycle are gene mutations most likely to occur?
) Interphase
Gene mutations occur spontaneously.
(i) During which part of the cell cycle are gene mutations most likely to occur?
……………………………………………………………………………………………….
(1)
(ii) Suggest an explanation for your answer.
) DNA / gene replication / synthesis occurs / longest stage
What are the 2 main ways of controlling gene expression
- prevent transcription
- destroy MRNA before translation
Give and outline 2 ways that transcription and translation can be regulated
- Via transcriptional factors- bind to promoter regions upstream from a gene and stimulate gene expression by helping RNA polymerase to bind
- RNA interference-involves cutting up MRNA
Describe how TF are involved in transciprion
- TF are need to bind to DNA’s promoter region just behind the gene for transcription
- TF are complimentary to the DNA
- TF move from the cytoplasm TO nucleus if cell recieves message
- When TF binds to DNA transcription is initiated (rna polymerase binds) and MRNA is made
- TF that activate transcription are ACTIVATORS
How can TF prevent gene expression
- By binding upstream of the target gene and preventing RNA polymerase from binding aka REPRESSORS
- If the shape of the TF prevents TF binding to the DNA upstream of the gene (DNA BS CAN’T BIND TO DNA) and so can’t bind so transcription is inhibited
How can oestrogen initiate the transcription of target genes
- ostreogen is a steroid hormone that can affect transcription by binding to a TF called an OESTROGEN RECEPTOR, forming an oestrogen-oestrogen receptor complex
- The complex moves from CYTOPLASM TO NUCLEUS where bonds to SPECIFIC DNA SITES near start of the target gene
- Complex acts as an activator of transcription by helping RNA poly. Bind to the target gene
- Complex can also Prevent escpression by acting as a REPRESSORS so prevent rna polymerase binding
- What the complex does depends on cell and target gene
How can RNA interference (RNAi) prevent gene expression
- Cut up MRNA before it can be translated using small double-stranded sections of RNA called siRNA
- In cytoplasm, siRNA associates with several proteins and unwinds and 1 strand binds to the target MRNA.
- Base seq. of the siRNA is complimentary to the base sequence in sections of the target mRNA
- Protein cut MRNA into fragments so can’t be translates and move into processing body (tools to degrade)
- Similar in plants
-
Why is RNA interference less efficient in controlling gene exression than eg transcription factors?
MRNA already synthesised and used energy
How can RNA interference be used by cells to defend against viruses
siRNA complimentary to viral MRNA can be produced which prevents translation of viral proteins
How can RNA interference be applied IRL?
- Identify functions of genes in cells or simple organisms by silencing the gene and observing the effects
- Genetically modifying crops by silencing undesribale genes
- Treating patients to silencing cancer ces or other g few netix disease or in antiviral therapies
What are epigenetics
A heritable change in gene function/expression/activity without changing the DNA base sequences which can be caused by the environment resulting in a change of phenotype
How does increased methylation affect DNA?
- Methyl groups added to cytosine bases
- Prevents transcription factors from binding to promoter regions of DNA.
- Attracts proteins that condense chromatin (DNA-histone complex) so prevent transcription as RNA polymerase can’t bind
How does decreased acetylation affect histones?
- Histones become more positively charged. attracts phosphate groups on DNA as phosphate is negatively charged
- Causes chromatin to condense so TF and RNA polymerase cant bind
Summarise the affects of increased methylation AND decreased acetylation of causing cancer
Increased methylation INHIBITS TSGs so tumours form.
Decreased acetylation INHIBIT proto-oncogenes so inhibit tumour formation
Introns VS exons
Introns are non-coding sections of DNA, exons are
What can cause silent/neural mutations
- mutations in the introns
- mutations changing the tertiary structure of the protein has no major effect on the organism
What is a translocation mutation and does this have a significant effect
- One group or seq of bases moved from one location to another- may be on the same chromosome or on another
- May Lead to signif effects on phenotype because on different genes on different chromosomes
What causes mutations
- spontaneous error in DNA replication
- chemical mutagens- benzene, alcohol. asbestos. tobacco
- Ionising radiation- UV, x-ray, alpha, beta
Explain how a substitution mutation would lead to the formation of a non-functioning protein
- A change in the amino acid seq leads to a change in hydrogen bonds in the tertiary structure, so the substrate is no longer complementary to the enzyme’s active site
The faulty allele that causes EVC syndrome is the result of a mutation of a gene called EVC which leads to the production of a protein that has one amino acid missing. Suggest how a mutation can lead to the production of a protein that has one amino acid missing.
3 bases lost
Suggest how the production of a protein with one amino acid missing may lead to a genetic disorder such as EvC syndrome
The tertiary structure changes, so the enzyme is non-functional
Describe what is cancer?
- Result of mutations in genes that control mitosis
- Results in uncontrollable division of cells and therefore the formation of a tumour
- Tumours can be benign or malignant
Characteristics (4) of benign tumours
- can grow large but at a slow rate
- non-malignant so can’t spread
- surrounded by a capsule and contain adhesion molecules so compact and can be removed by surgery
- localised
Characteristics (4) of malignant tumours
- grow largely
- have the ability to spread to other parts of the body via MESTASIS
- develop their own blood supply
- can be life-threatening and often need supplementary treatment e.g chemotherapy
Describe what oncogenes are
- mutated versions of proto-oncogenes
- encode proteins involved in DNA replication and mitosis
- can be permanently switched on causing excessive cell division and tumour formation
- hypomethylation increases expression as chromatin will be less condensed
Describe tumour suppressor genes
- encode proteins that inhibit cell division and cause apoptosis
- if a mutation occurs, apoptosis is inhibited and cell division is stimulated leading to uncontrollable cell division and tumour formation
- hypermethylation leads to increased expression as chromatin is condensed so the gene’s transcription is limited
Explain how the methylation of TSGs can lead to cancer
increased methylation prevents transcription of TSGs so the protein that inhibits cell division isn’t produced so the mitosis isn’t controllable
Describe what stem cells are
- undifferentiated cells that continually divide and become specialised
- types include totipotent, pluripotent ,multipotent and unipotent
what are totipotent stem cells
- stem cells that can differentiate into any type of body cell-during development these totipotent stem cells can only translate part of their DNA, resulting in specialisation
- only occur for a limited time in early mammalian embryos
describe what pluripotent stem cells are and what are the issues surrounding using pluripotent stem cells
- found in embryos
- can divide unlimited times and into almost any type of cell
- used in treating human disorders e.r re-growth of damaged skin cells
- stem cells can continue to divide so could form tumours
- destruction of embryo
- should humans be cloned etc
Describe multipotent and unipotent stem cells
- found in mature mammals
- multipotent= differentiate into limited number if cells e.g bone marrow have WBC AND RBC
- unipotent= only differentiate into one type of cell e.g. cardiomyocytes
Describe what iPS cells are and what are its pros
-created from adult unipotent cells (somatic)
-treated with transcription factors to switch on genes that induce pluripotency (undifferentiated)
………………………….
-PROS:
don’t cause embryonic destruction, self-renewal so divide indefinitely, used in medical treatment instead of embryonic stem cells
papaya plants reproduce sexually by means of seeds. Papaya plants grown from seeds are very variable in their yield. Explain why
crossing over during meiosis and the random fertilisation of gametes
explain the advantage of growing papaya plants from tissue culture rather than from seeds
will be genetically identical
what is a genome
- full set of genes in each cell
- can be sequenced
what do sequencing projects do
- read the genomes of a variety of organisms
- determining the genome of simple organisms allows the sequence of the proteins that are encoded
what are useful applications of sequencing projects
- identification of potential antigens to use in vaccines
- allows genome-wide comparison between different species, allowing the determination of evolutionary relationships
- beneficial to medical research as genome comparisons between individuals can allow the development of personalized medications
what are proteomes
the full range of proteins that can be encoded by the genome
whats the significance between the human genome project
The HGP determined the sequence of bases in a human genome.
- used ins screening of abnormal/mutated sequences allowing the identification of disorders before the symptoms arise
- pre-implantation screening
How can you calculate the number of DNA fragments prod by a given number of cycles
2(X)
X= number of cycles
