Genetics semester 1 Flashcards
What are Mendels three laws?
- Segregation
- Independent assortment
- Dominance
Is a amoebe unicellular or multicellular?
Unicellular.
When mating types 1 and 2 meet what happens?
They form a plasmodium.
What do plasmodium eat?
Amoebe.
Does the plasmodium show the genotype or the phenotype?
Genotype.
Do the plasmodium have a type?
No.
What are aspergillus nidulans?
Asexual spores with one nuclei and a coloured pigment.
What colour is mycelium?
They are colourless.
Do conidia or mycleium have thread like hyphae?
Mycleium.
Where do the conidia get their colour from?
Through the colourless mycelium.
What two processes make up nuclear cell division?
Karykinesis and cytokinesis.
What is the definition of variance?
Tendency for offspring to differ from parents.
What is the definition of heredity?
Tendency of offspring to resemble parents.
What did Jennifer Dees experiment with mating type show?
That there is more than one allele per gene.
What is chimera?
When there is more than one genotype per zygote. This is naturally rare in humans.
What is the definition of totipotency?
Ability of a cell to give rise to a whole new organism.
What is cytogenetics?
The connection between the behaviour of chromosomes and the behaviour of genes.
What is a centromere?
The constriction on each chromosome.
How many identical cells does there need to be for it to be considered a clone.
More than 2.
There are 10^14 clone cells in the body with how many different morphogens?
200.
What are two consequences of mutations?
Apoptosis or cancer.
Do haploid or diploid organisms go through mutations?
Both.
Is AB/ ab described as cis or trans?
Cis.
Is Ab/Ba described as cis or trans?
Trans.
What are the ends of chromosomes called?
Telomeres.
What arm is (P)?
The short arm.
What arm is (Q)?
The long arm.
What is chromatin a mix of?
Protein and DNA.
What protolytic enzyme allows G banding?
Tripsin.
What is the stain called that G banding is involved in?
Giasma stain.
Which sex chromosome is smaller?
Y.
What type of proteins allow sister chromatid cohesion?
Glue proteins.
What happens at the end of the spindle fibres allowing them to shorten?
Depolymerisation.
What is euchrochromatin?
Loose DNA which is transcribed.
What is heterochromatin?
Tight DNA that is not transcribed.
What can prophase be separated into?
Prophase and prometaphase.
What is nordisjuction?
Failure of normal segregation.
What does the chiasma do?
Helps hold the bivalents together.
What disorder does XO show?
Turner syndrome.
What disorder does XXY show?
Sex klinefelter.
What is the genetic notation for a Down’s syndrome female?
47 XX +21
What is the notation for Cri Du Chat?
46 XX 5P-
What is the definition of heredity?
Transmission of characteristics from parents to offspring by the means of genes.
What does aneuploidy mean?
An incomplete set of genes. Either too many or not enough.
What type of aneuploidy is trisomic?
2n+1.
What type of aneuploidy is monosomic?
2n-1.
What type of aneuploidy is nuclisomic?
2n-2.
What type of aneuploidy is disomic?
n+1.
Duplication can be tandem or ______.
Insertional.
What happens in an inversion of DNA?
The segment is cut out, flipped and reversed.
In a paracentric inversion is the centromere inside or outside?
Paracentric- outside
Pericentric- inside.
How many chromosomes are there before and after mitosis?
46
There are 92 chromatids before and no chromatids after.
Is meiosis 1 or 2 a reduction division?
1.
Is meiosis 1 or 2 an equational division?
2.
When do bivalents form in meiosis?
Prophase 1.
What type of segregation happens in tetrads.
2:2 segregation.
Is Mendels law of independent assortment always true?
No.
What holds together tetrads?
Membrane sacs called ascus.
What type off cross over do you need to make a tetrad with a non parental diatype?
A double cross over.
What needs to be restrained to get ordered tetrads?
Meiosis.
For a tetrad to be all recombinant what needs to happen?
A four strand double cross over.
When there are no cross overs what type of segregation has occurred?
First division segregation.
When one cross over has occurred when type of segregation has happened?
Second degree segregation.
The probability of a cross over between two genes is roughly proportional too?
The distance between them.
What holds chromosomes together until anaphase 1?
Cross overs.
If a cross over is unlikely are there more parentals or recombinants in the progeny?
Parentals.
In tetrads if there is less NPD then P what can it show?
Linkage.
What does Mendels second law not apply too?
Linked genes.
What does the recombination frequency equal?
Recombinants/ total meiotic products x 100.
Why is the maximum combination frequency 50%?
Because if the genes lie far enough apart is it equally likely that they will be P or R.
What does a polymorphic population mean?
Two or more alleles are present at a significant frequency of more than one.
How do you calculate allele frequency?
)No. of allele A)/ 2N.
What 3 assumptions do you have to make for Hardy Weinburg to be true?
No mutation, no migration, random genetic drift.
What is the founders effect?
When a breeding female moves out of a population to make a new one, for example on the Galápagos Islands.
What does positive assortative mating involve?
Choosing a mate if they have the same phenotype as you.
What does positive assortative mating occurs what to do you end up with more off?
More homozygous in the population.
Allele frequency is not changed.
What does negative assortative mating ( avoiding choosing a mate with similar characteristics as yourself) increase?
The frequency of heterozygous in a population.
When will natural selection not act against an allele?
When it has no effect on the phenotype.
What can transient polymorphism be followed by?
Fixation of an old or new allele.
What is pleiotropy?
When one gene affects more than one phenotype.
What are the three types of dominance?
Simple, incomplete and over dominance.
What does Darwinian fitness show (W)?
The ability for an individual to pass on a gene.
What is S?
The selection coefficient.
What equation relates W and S?
W = 1-S.
If selection is acting against a recessive allele what genotype will increase in the next generation?
Homozygous dominant.
What happens as allele frequency decreases?
Selection is less efficient.
What equals the percentage of A in the homozygote?
The frequency of the recessive allele.
What can selection against an allele be balanced by?
Mutation to that allele.
There is a high frequency of the allele for cystic fibrosis. Why is this believed to be the case?
It is thought that in the past there was a heterozygous advantage for a increased resistance to cholera in mice and an increased resistance to tb in humans.
How many people carry cystic fibrosis?
1 in 22.
What happens mutagenesis?
A wrong base is incorporated into the replication fork. This happens in S phase.
What is an independent mutant?
A mutant which has arised from a independent mutation event.
How do you determine how many mutations a mutant carries?
Cross with a wild type.
What ratio is found when there is one mutant?
1:1.
What ratio is found when there are more than one mutant?
1:3 or 3:1. That downers on wether having one mutant shows the mutant phenotype.
What does allied mutants mean?
Mutants are on the same gene.
What does non alleleic mutants mean?
Mutants are on a different gene.
What two tests can you use to test for allelism?
Recombination or complementation test.
In the test of recombination do allelic or non allelic mutants give rise to a wild type?
Non allelic.
What genes could you mistake for allelic in the recombination test?
Genes which are closely linked.
How are genes with related functions often organised throughout the genome?
They are spread out.
In the complementation test what do you look at?
The diploid phenotype.
In the complementation test what will allelic mutants give rise to?
A mutant diploid.
In the complementation test what will non allelic mutants give rise to?
A wild type diploid.
For complementation to work what do all mutants have to be?
Recessive.
What is a complementation group?
A set of mutants that fail to compleat each other, therefore identifies a gene.
Apart from diploids, what else can the complementation test be used on?
Heterokaryons (cells with more than one haploid nucleus, such as fungi.)
Why does it not matter in a heterokaryon that the WT are in different nuclei?
Protein synthesis occurs in the cytoplasm.
What order is the birth order shown as on a human pedigree?
Left to right.
What is a proposituts/ proband/ proposita?
An individual which brought that human pedigree to attention.
What is penetrance?
Proportion of individuals with a particular genotype which the corresponding phenotype.
What is expressivity?
The extent that individual with a particular genotype shows the corresponding phenotype.
On a probability tree do you follow genotypes or phenotypes?
Phenotypes.
What is a physical map based on?
Gene sequence directly.
What is a linkage group?
A set of gene loci that are known to lie on the same chromosome.
What two steps does mapping a gene involve?
- Assignment to a linkage group.
2. Determining the position within a linkage group.
Why can’t a normal cross be used to show linkage?
As for 15/16 of the progeny the exact genotype may not be known.
What does a test cross involve?
A double heterozygous parent and a homozygous recessive parent.
What do test crosses allow you to do?
Work out the recombination frequency and with it construct a linkage map.
Note in haploids you can directly look at mitotic products.
How are cytological maps made?
Visualising DNA to check for any visible mutations.
What can a linkage of 50% also show?
That genes lie on different chromosomes.
What is the purpose of a three point cross?
To determine the relative map position if three genes which lie in a single linkage group.
What is a double cross over?
When a group is mistaken as parental with respect to the flanking makers.
What is a cM equivalent too?
I cross over per 100 gametes.
What is the equation for map distance?
(SC1 + SC2 + 2DCO) / 100
Do double cross overs cause the map distance to be over or underestimate the distance of the flanking markers?
Overestimate.
What’s the best way to estimate map distance?
The sum of the intermediate RFs.
Up until what percentage is there a linear relationship between cM and RF? Why?
10%
As at small distances there is less chance of generating double cross overs.
What class is always the largest class when looking at constructing a three point cross?
The parental.
What class is the smallest class when constructing a three point cross?
The DCO class.
What is interference?
The occurs be of one crossover may effect the chance of another cross over near by.
How can you show interference?
By looking at the actual number of DCO and calculating the expected amount of double cross overs with the product rule. The numbers will not add up as the events are not independent.
What is the coefficient of coincidence?
Observed DCO/ Expected DCO.
If the coefficient of coincidence is 0 what does this show?
High interference / cross overs are very close together.
What is the equation for interference?
1- coefficient of coincidence.
Do mitochondrial genes for Mendelian inheritance?
No.
What is Anisogomy?
Gametes are dimorphic.
What is isogamy?
Gametes are morphologically identical.
Is isogamy is maternal inheritance followed?
Almost always but is called uniparental.
How big is the human mitochondrial genome?
17kb.
What is encode for by mitochondrial DNA?
Genes for protein synthesis machinery and genes for subunits of the mitrochondrial electron transport chain.
What is LHON?
Leber’s Heredity Optic Neuropathy / a disease caused by mutations in mitrochondrial DNA.
What is heteroplasmon?
A cell with more than one genotype. Often due to mutation.
What is a homoplasmon?
A cell with one genotype. All cytoplasmic genomes are the same.
In a heteroplasmon do you need the wild type genotype of the mitochondrial DNA to be alive?
Yes.
How long is M phase?
30-45 minutes.
How long is S phase?
6-8 hours.
How long is G1?
6-8 hours.
How long is G2?
4-6 hours.
What is the MTOC?
Microtubule organising centre.
What is the animal MTOC composed off?
2 centrioles and tubulin subunits. It is a double structure.
When so the spindles attach to the centromeres?
When the nuclear envelope breaks down.
What is the metaphase plate?
It represents chromosomes on the equator of the spindle.
What is disjunction?
When anaphase separates chromosomes.
Where are kinetochore proteins found?
At the centromere.
What enzyme breaks down sister chromatid cohesion?
Separase.
What is present at the centromere to prevent separase from acting?
Shugoshin.
What does the kinetochore interact with?
Ends of microtubulin in the spindle.
What end do microtubules grow from?
Positive end.
What do the astral microtubules do?
Anchor the spindles and MTOC to the cell cortex.
What ends are present at the MTOC?
Negative.
What happens to the kinetochore microtubules in anaphase one?
Motor proteins move towards the negative end causing depolymerisation and shortening.
What happens to the polar microtubules in anaphase 2?
They lengthen due to polymerisation at the negative end. Motor proteins move towards the positive ends.
What happens to the astral microtubules in anaphase 2?
The polar ends extend and they shorten. Motor proteins cause depolymerisation at the positive end.
What type of microtubule does the centromere attach to?
Kinetochore microtubule.
What is a conditional mutant?
A mutant than can only progress through one of two conditions. If it can progress through both then it is WT.
What did Hartwell discover?
CDC.
What temperature is permissive/ non restrictive?
Low.
What temperature is non permissive/ restrictive?
High.
What is a selective technique?
A technique where only one phenotype can survive- the best technique to use.
What technique did Hatwell use?
The screening technique with velvet replica planting.
What two temperatures did Hartwell use?
23 and 36.
What does a asynchronous population contain?
Cells at all stages of the cell cycle.
What does CDC28 do?
Play a key role in the initial decision of if the cell should proceed through the cycle.
What organism did Nurse use to isolate CDC?
S. Pombe.
What does CDC2 control?
G2 progressing into M.
What corresponding gene to CDC28/ CDC2 is found in humans?
CDK1.
What did Hunt discover?
Cyclins.
When is cycling synthesised?
Continuously.
When is cycling destroyed?
During mitosis.
CDC28, CDC2 and CDK1 are all what?
Cycling dependant protein kinases.
What does progression through the cell cycle dependant on?
Cycling availability.
What cyclin dependant kinase is found in yeast?
CDC28. It does however have more than one cyclin.
Do mammals have multiple cyclin dependant kinases?
Yes. They also have multiple cyclins.
When is mitotic cyclin at critical concentration?
At the end of G2.
When CDK and cyclin form the active complex what do they do?
Carry our phosphorylation activities including targeting protein degradation.
How does the cyclin/CDK complex become active?
It is phosphorylated by other kinases.
How are the 2 inhibitory phosphates removed?
Phosphatase activity from the active form of CDK/cyclin.
How many activating phosphates are associated with CDK/ cyclin complex?
One.
What type of feedback does the CDK/cyclin complex use?
Positive.
How is the anaphase promoting complex switched on?
It is phosphorylated by the CDK/cyclin complex.
What does the anaphase promoting complex do?
Promotes separase activity by targeting securin for degradation.
What is separase complexes with?
Securin.
How can you activate separase?
Degrade securin.
What is APG?
A ubiquitin ligase. It targets other proteins to be destroyed.
What does G1 CDK/cyclin do?
Decides if the cell should leave G1 and enter S phase.
What activates EF2 transcription factor?
G1 CDK/cyclin.
What is EF2 normally bound to?
Rb protein.
How is rb destroyed?
It is directly phosphorylated by G1 CDK/cyclin.
What are checkpoints also known as?
Transition points.
What checkpoint commits the cell to completing the cycle?
G1 checkpoint.
When is DNA damage permanently incorporated into the genome?
Once it has gone through a phase and passed the replication fork.
What does the G2 checkpoint check?
If the cell is ready to divide.
What does the metaphase checkpoint check?
If all the chromosomes are attached to the spindle.
