The Genetic Basis of Evolution

Question 1

What is meant by a gene?

Answer 1

it is a section of DNA composed of a regulatory and transcribing region

Question 2

What effect does a gene have on the phenotype?

Answer 2

it is the segregating and heritable determinant of the phenotype

Question 3

What is meant by a loci?

Answer 3

position on the chromosome

Question 4

What is meant by an allele?

Answer 4

a different version of a gene

Question 5

What are the two versions of an allele?

Answer 5

dominant and recessive

Question 6

How do you work out allele frequency?

Answer 6

(2×Homozygotes + Heterozygotes) / total

Question 7

What is meant by a genotype?

Answer 7

the genetic makeup of an individual, it describes the gene frequencies

Question 8

When alleles are rare what genotype are they typically found in?

Answer 8

heterozygous

Question 9

What is the missing axis label?

Answer 9

proportion of allele copies that occur in heterozygotes

Question 10

What is the missing axis label?

Answer 10

Allele frequency

Question 11

What is meant by phenotype?

Answer 11

the physical/behavioural characteristics of an individual

Question 12

What influences a phenotype?

Answer 12

genes and environment

Question 13

What is meant by a gamete?

Answer 13

the germline cells which combine with the gamete from the opposite sex in fertilisation to produce a zygote

Question 14

What is meant by a zygote?

Answer 14

the earliest developmental stage of an embryo

Question 15

What is meant by evoltution?

Answer 15

a change in allele frequency overtime

Question 16

What is meant by pan-selectionism?

Answer 16

everything can be explained solely by selection

Question 17

What is meant by a null hypothesis?

Answer 17

a general statement that states that nothing new is happening

Question 18

What is the null hypothesis for evolution?

Answer 18

Hardy-Weinberg Equilibrium

Question 19

What are the assumptions for the Hardy-Weinberg Equilibrium? (8)

Answer 19

1. Organisms are diploid
2. They reproduce sexually
3. Generations are non-overlapping
4. Mating is random​
5. Infinite Populations
6. No mutations
7. No migration
8. No selection or drift

Question 20

What does it mean if generations are described as non-overlapping? Explain using ‘generation A’ and ‘generation B’

Answer 20

Generation A does not mate with generation B

Question 21

What do all allele frequencies equal?

Answer 21

1

Question 22

State the two equations true to the Hardy-Weinberg Equilibrium

Answer 22

P + Q = 1

P² + 2PQ + Q² = 1

Question 23

If all the assumptions of the Hardy-Weinberg Equilibrium are met then what would we expect?

Answer 23

the allele frequencies to stay the same and therefore no evolution

Question 24

What is meant by genetic drift?

Answer 24

the process where allele frequencies change overtime due to the effects of random sampling

Question 25

What is genetic drift a consequence of?

Answer 25

a finite population size

Question 26

Is genetic drift evolution? Why?

Answer 26

Yes

because drift causes a change in allele frequencies overtime

Question 27

What is the relationship between selection and drift?

Answer 27

selection happens against a background of drift

Question 28

What will the overall trend in drift be?

Answer 28

• random direction
• not one smooth line, there will be dips

Question 29

If an allele frequency has increased in generation A what is it likely to do in generation B?

Answer 29

continue increasing

Question 30

What is meant by fixation?

Answer 30

When you only have one allele present due to the loss of an allele

the chance of getting the remaining allele is 1

Question 31

When is genetic drift stronger?

Answer 31

in smaller population sizes

Question 32

What is likely to happen to allele frequencies if my population size decreases?

Answer 32

more likely to fixate

drift becomes stronger

vast change in allele frequencies

Question 33

What is meant by a bottleneck?

Answer 33

a drastic reduction in the size of a population

Question 34

What happens to drift during bottlenecks? Why?

Answer 34

drift becomes stronger

because the population size is smaller

Question 35

Why does selection occur?

Answer 35

different fitness levels

Question 36

If we say something is fit, what am I referring to?

Answer 36

the genotype

Question 37

What would we expect from a more fit individual?

Answer 37

to survive

be able to pass on their genes to offspring

Question 38

If selection is occuring what would we expect fitness levels to be like?

Answer 38

Different between individuals

Question 39

What would happen if all fitness levels were the same?

Answer 39

• there would be no selection
• the population is evolving neutrally
• drift is still occuring

Question 40

What are the two ways fitness can be measured?

Answer 40

absolute fitness and relative fitness

Question 41

Describe how you would measure absolute fitness

Answer 41

you measure this by measuring the change in the abundance of a genotype from one generation to the next

Question 42

Describe how you would measure relative fitness

Answer 42

you would divide the fitness of one individual by the greatest fitness present

Question 43

Under relative fitness, what would the highest fitness have a value of?

Answer 43

1