Mutations

Question 1

what is a mutation in general terms?

Answer 1

ultimate source of variation
the change in structure of a gene which results in a variant form which may be transmitted to subsequent generations caused by alteration of base units/genes

Question 2

why do we need mutations?

Answer 2

without every genetic locus would fix and there would be no evolution so no variation
without all individuals would be genetically identical

Question 3

what are point mutations?

Answer 3

synonymous - silent - don’t change final product
nonsynonymous - miscense - changes a codon
nonsense - stop
read through

Question 4

how is sickle cell anaemia caused by mutations?

Answer 4

point mutations - single base substitution in HbB gene

sickle cells occur bc the HbB molecules from the mutated gene stick together - form chains

Question 5

symptoms of sickle cell anaemia?

Answer 5

breathlessness, fatigue, extreme pain and vulnerability to disease

Question 6

what is caused by insertion and deletion mutations and how?

Answer 6

cystic fibrosis - deltaF508 mutation
mutation causes abnormal folding and fast degradation
increased water retention in cells and cascade effects on body - including thicker mucous membranes - obstruction of airways and infection

Question 7

what is a frameshift mutation and ORF?

Answer 7

DNA has 6 possible reading frames

ORF - open reading frame - the part between the start and stop codons that can be translated

Question 8

what happens when you have indels without the coding sequence?

Answer 8

1. RNA polymerase can’t bind if the core promoter is deleted - no transcription
2. regulatory sequence deleted so transcription factors can’t bind so uncontrolled transcription

Question 9

what are chromosomal mutations?

Answer 9

a change in the number or structure of chromosomes

can move genes around - one end to another or one chromosome to another

Question 10

how does deletion work?

Answer 10

loss of all or part of a chromosome caused by (unrepaired) breaks in the chromosome
e.g intellectual disability - symptoms caused by disruption of neuronal migration - most cases not inherited but occurs during gamete formation

Question 11

how does duplication work?

Answer 11

provides extra copy of all/part of chromosome - errors in DNA replication/repair

Question 12

why is duplication good?

Answer 12

major mechanism for generation of new genetic material - evolutionary innovation - redundancy means reduced selection pressures on the second copy

Question 13

what is polyploidy an example of?

Answer 13

whole genome duplication

its when there is 2 or more sets of homologous chromosomes

Question 14

what causes polyploidy?

Answer 14

problems in gamete formation

Question 15

what is polyploidy speciation?

Answer 15

when the polyploid plant is not compatible with the ‘parent’ plant

Question 16

what is translocation?

Answer 16

when one part of one chromosome breaks off and attaches to another

Question 17

what disease is caused by translocation?

Answer 17

downs - trisomy 21 - 3 copies of the 23rd chromosome

Question 18

what is inversion?

Answer 18

when the direction of parts of a chromosome are reversed - found as fixed differences between species or segragating within populations of the same species
recombination reduced

Question 19

what is inversion key in?

Answer 19

supergene formation
tight clusters of two or more genetic loci - each locus affects a different trait
certain allele for one locus then becomes linked to a certain allele of a second locus
this gives integrated control of complex phenotypes and then segragtes within a species

Question 20

what is shown in swallowtail butterflies?

Answer 20

batesian mimicry

Question 21

what did fisher predict with Batesian mimicry?

Answer 21

that imitating would require both strong selection and specific trait combos

Question 22

what is dsx?

Answer 22

a transcription factor which regulates somatic sexual differentitation across insects
ensures femaleness genes are switched on and male genes off
three forms - two in wings

Question 23

what was the goal of fishers ‘geometric model of adaptation?

Answer 23

predict whether any random mutation will be adaptive given its effect size
smaller mutations have higher chance of being advantageous

Question 24

what did motoo kimura think

Answer 24

Fisher - probability that a mutation of a given size will be advantageous
but thought fisher had overlooked
- probability of mutation being fixed
- mutations of small effect are less likely to be fixed
derived the distribution of sizes among mutations ‘used’ in adaption

Question 25

what did motoo kirmura conclude?

Answer 25

mutations of intermediate phenotypic effect are the most likely to play a role in adaptation

Question 26

what was the overall conclusion of fishers model?

Answer 26

mutations of large effect are more likely when the current trait is far away from the optimum