T8

Question 1

mutations importance

Answer 1

provides genetic variation to allow for natural selection to occur
- mutation occurs in germline then it will be passed on to next generation

Question 2

effects of mutation

Answer 2

synoymous mutations cause no change in phenotype even though the amino acid sequence different as the same protein is being coded for - unseen

non synoymous mutations - do cause a change in phenotype and protein when a change to amino acid
- usually bad but sometimes good

• mutations can affect regulation sequence, the structure of a protein, or could be silent if in non coding regions or introns

Question 3

deleterious mutations

Answer 3

mutations that negatively affect the fitness when affecting the phenotype
- mutations with bigger effects are more likely to be deleterious
- mutations with smaller effects less likely

Question 4

graphs and mutations

Answer 4

if draw a circle on a graph with two traits that show the highest fitness phenotype and where the population currently is, that gives the circumference for mutations that can be positive
- if mutation moves phenotype into the circle and closer to highest fitness then it is good
- if mutation moves phenotype out of the circle then it is bad

Question 5

circle and mutations on the graph

Answer 5

if a small circle then that shows the population has been evolving in the same environment of a while so harder for mutations to have a positive effect

however if a change to the environment then the current population is less adapted so a bigger circle as they are further away from highest fitness so more likely that mutations will be a positive and bigger drive for natural selection

Question 6

randomness and mutations

Answer 6

mutations are random
- they will occur independent of how useful it is to the environment - mutations are not directed

does not mean that every mutation has an equal likely hood of occuring

Question 7

early measures of genetic diversity

Answer 7

these relied on mutations with obvious phenotypic effects butttt
- molecule biology has changed these views as now able to study protein structure which showed that there is much more variation than we thought

Question 8

neutral mutations and maintaining variation

Answer 8

majority of variation is due to neutral mutations
- mutations that have no effect on phenotype or fitness
- so they are unaffected by natural selection and determined randomly
- meaning that alleles can persist in population for a long time, giving variation

variation is maintained in this sense because selection cannot act to remove it

Question 9

mildly deleterious mutations and maintaining variation

Answer 9

some variation is accounted by this
- these reduce fitness by a small amount
- variation maintained by mutation-selection balance
- selection is weak when mutations have small effects as relative fitness is still quite high

example
- if a perfect population arises and DNA mutations occur then these mutations will be deleterious as the population was already well-adapted

so selection acts to remove these as they decrease fitness but as only mildly bad effects, the selection occurs slowly until reachs an equilibrium where the rate of new mutations is the same as those selected out

variation is maintained because selection is inefficient at removing the mildly bad mutations

Question 10

disruptive selection and maintaining variation

Answer 10

disruptive selection leads to diverse types of traits existing in same population
- so this means lots of variation

Question 11

frequency dependent selection

Answer 11

the fitness of the genotype depends on its frequency in a population

the fitness of each gene decreases as they become more common as there is more competition between those with the same alleles

Question 12

what does frequency dependent selection mean for a population

Answer 12

this means that there is usually a cycle of flucation of alleles in a population to maintain the variation

Question 13

heterzyogte advantage

Answer 13

this is where the heterozygote is the fittest
Aa is maintained in a population

Question 14

genetic variation between population

Answer 14

looks at the forces for this

Question 15

local adaption

Answer 15

the environment varies from place to place

the fittest phenotype in an place varies

local adaption acts to maintain genetic variation between populations as different alleles are fixed in different population

to prove this - the adaption the populations have are best fittest for their environment only

Question 16

random diverage

Answer 16

this is the absence of natural selection

the frequency of neutral alleles is determined by genetic drift

because these are random processes, then they will act independently in populations, maintaining variation

Question 17

migration

Answer 17

movement of one population to another - gene flow between them and carrying alleles between population
- this leads to the populations homogenising and becoming more genetically similar

it reduces genetic diversity between populations but may increase genetic diversity within a population as new alleles brought in

Question 18

gene flow

Answer 18

it counteracts divergence and randomness