Lecture 3 - Heredity

Question 1

What is variation?

Answer 1

Individuals differ in phenotype

Question 2

What is heredity?

Answer 2

Offspring resemble their parents

Question 3

What is competition?

Answer 3

There is differential reproductive success between individuals - some variation more advantageous than others

Question 4

What did Mendel find in his pea breeding experiments?

Answer 4

One green parent, one yellow parent
in F1- generation 1 - all 4 peas were yellow
in F2 - 3 yellow and 1 green

Question 5

What do Mendel’s findings suggest?

Answer 5

There must be 2 factors deciding on the colour (each parent)
There must be asymmetry (yellow more dominant that green)

Question 6

What is A and a?

Answer 6

The two types of hereditary particle (alleles of a gene)

Question 7

What is meant by homozygous?

Answer 7

Having two copies of the same allele

Question 8

What is meant by heterozygous?

Answer 8

Having one copy each of two different alleles

Question 9

What is a dominant gene?

Answer 9

Expressing its phenotypic effect when one or more copy is present

Question 10

What is a recessive gene?

Answer 10

Expressing its phenotypic effect only shen two copies are present.

Question 11

What is a punnett square?

Answer 11

Used if we know the genotypes of parents, then we can predict the probabilities of given genotypes and therefore phenotypes to the offspring

Question 12

Are the probabilities of punnet squares equal/

Answer 12

yes - 25%

Question 13

What happened when mendel added an allelic characteristic of smoothness to the green pea?

Answer 13

Predicted 1st generation all yellow
Predicted 3 yellow 1 smooth green for 2nd generation

Actually found:
- 1st generation all yellow
- 2nd generation some yellow, yellow smooth, some green, some smooth green - so combinations of phenotypes that never existed

Question 14

What are the explanations for Mendel’s experiment of the smoothness of the pea?

Answer 14

There must be two different genes controlling colour and smoothness.
They must be on separate chromosomes and be passed on independently of one another.

Question 15

What is the double punnett square?

Answer 15

Used in the case of there being 2 genes
So two genes A and B
Two alleles each, A a B b

Question 16

How many possible genotypes are there in a double punnett square?

Answer 16

16 possible genotypes

Question 17

How many possible phenotypes are there in a double punnet square?

Answer 17

4

Question 18

What is the Hardy-Weinberg theorem?

Answer 18

Allele frequencies in a population remain constant unless one or more factors cause the frequencies to change.
It predicts frequencies of genotypes in a population.

Question 19

What are the equations for the Hardy-Weinberg theorem?

Answer 19

p^2, 2pq and q^2 - all different ways we can calculate what proportion of individuals will have this phenotype

Question 20

What is genetic drift?

Answer 20

Because populations are finite, allele frequencies therefore change by chance from generation to generation

Question 21

What does genetic drift suggest about neutral alleles?

Answer 21

Genetic drift can cause some neutral alleles to increase in frequency and others to disappear, even though they offer no advantage or disadvantage to survival

*	As a result, populations can become genetically different at the molecular level just by chance, even if they started out genetically similar.

Question 22

What is genetic drift useful for?

Answer 22

Tracking evolutionary descent

Question 23

Is genetic drift seen more in larger or smaller populations?

Answer 23

Smaller - can see more change in smaller populations

Question 24

Quantitative genetics is based on

Answer 24

phenotypic correlations between relatives - allows us to infer how much variation in the phenotype we see is because of the genotype in relatives

Question 25

Which type of twin show a more positive correlation in height?

Answer 25

Monozygotic twins - less strong for Dz as share less genes

Question 26

What are the components of variation?

Answer 26

G or A: Variation due to genes C: Variation due to shared environment E: Variation due to unique or non-shared environment

Question 27

What do Mz twins share?

Answer 27

All of the genetic influence and all of the shared environmental influence

Question 28

What is the equation for the correlation of MZ?

Answer 28

corrMZ=G+C

Question 29

What do DZ twins share?

Answer 29

half genetic influence and all shared environment

Question 30

What is the equation for the correlation of Dz twins?

Answer 30

corrDZ = 1/2G + C

Question 31

If we take these correlation away from each other (corrMZ - corrDZ) what is showed?

Answer 31

1/2 G can be flipped to find out G G = 2 x (corrMZ - corrDZ) two times the difference in correlation of the twins - known as Falconer's estimate of heritability

Question 32

What is the meaning of h=1 and h=0 of heritability?

Answer 32

h=1 means - if height differs this is due to differences only in genotypes h=0 means - if height differs this is due to differences only in the environment

Question 33

Variation is measured between...

Answer 33

number between 0-1, which reflects the proportion of variation in the trait (height) in that population is due to variation in the genotype

Question 34

How does genetic recombination affect evolution?

Answer 34

It increases genetic diversity by creating new combinations of alleles.

Question 35

What is the principle of independent assortment?

Answer 35

Genes for different traits can segregate independently during the formation of gametes.

Question 36

Recessive vs dominant menedlian disease

Answer 36

recessive - cystic fibrosis dominant - huntingdons

Question 37

dominance, epistatic and additive effects

Answer 37

dominance - each allele adds small, independent effect to trait epistatic - alleles at different genes interact, one affecting another additive - each allele adds small, independent effect to trait

Question 38

broad-sense heritiability

Answer 38

proportion of phenotype variation explained by additive, epistatic and dominance effects

Question 39

polygenic

Answer 39

traits influenced by multiple diff genes

Question 40

What are the five assumptions of Hardy-Weinberg equilibrium?

Answer 40

1. No selection 2. No mutation 3. No migration 4. Random mating 5. Infinite population size (no genetic drift)