Lecture 11

Question 1

What are discrete phenotypic classes?

Answer 1

when a trait is influenced by a single locus

Question 2

How many phenotypes can 1 locus with 2 alleles make if it is additive?

Answer 2

3 phenotypes

Question 3

How many phenotypes can 2 loci with 2 alleles make if additive?

Answer 3

5 phenotypes

Question 4

How many phenotypes can 3 loci. with 2 alleles each make if additive?

Answer 4

7 phenotypes
*also the point where we start to see normal distribution of these phenotypes

Question 5

what are polygenic phenotypes?

Answer 5

A trait influenced by two or more loci

Question 6

What are quantative traits influenced by and what are they?

Answer 6

• they are traits that we measure in units
• influenced by many genetic loci
• influenced/interact with the environment

Question 7

What is quantitative genetics?

Answer 7

the study of the genetic mechanisms of continuous phenotypic traits

Question 8

What do traits that vary widely mean?

Answer 8

traits that vary widely about the mean have a bigger variance

Question 9

What is often formed by quantitative traits?

Answer 9

normal distribution
* when you have lots of genes combining to form a trait, you get normal distribution

Question 10

What is heritability?

Answer 10

the proportion of a population’s phenotypic variance that is attributable to genetic differences (does not consider environmental factors)

Question 11

What is the equation for H^2? (in words)

Answer 11

H^2=genetic variance/phenotypic variance

Question 12

What is the equation for H^2?

Answer 12

H^2=VG/VP

VP=VG+VE

Question 13

What is VP? VG? VE?

Answer 13

VP= total phenotypic variance in population

VG= variance due to genetic differences

VE= variance due to environmental differences

Question 14

How is heritability measured?

Answer 14

heritability is measured in a particular population at a particular place and time

Question 15

What is genetic variance?

Answer 15

similarity in genotypes at a site/loci

Question 16

what is environmental variance?

Answer 16

how much of the difference seen between individuals was reflected across environments

Question 17

what does it mean if the replicates of a genotype look identical in different environments?

Answer 17

all of the variation is due to genetic differences, and there are no environmental differences

Question 18

what does it mean if the replicates of a genotypes all look different in different environments?

Answer 18

the variance is due to environmental variance

Question 19

what is broad sense heritability?

Question 20

What is narrow sense heritability?

Answer 20

broad sense heritability, but we also measure the realized similarity between parents and offspring

Question 21

What is the difference between broad and narrow sense heritability?

Answer 21

The broad-sense heritability of a trait is the proportion of phenotypic variance attributable to genetic causes, while the narrow-sense heritability is the proportion attributable to additive gene effects

Question 22

What does it mean if the parent-offspring regression’s slope is 0?

Answer 22

the trait is not heritable

Question 23

What does it mean of the slope of the regression between parent and offspring is 0.5?

Answer 23

• the trait is somewhat heritable
• variation could be due to environment

Question 24

What does it mean if the slope of the regression between parent and offspring is 1?

Answer 24

• the trait it highly heritable
• all variation is due to genetic variation
• heritabilty for quantative traits is almost never 1

Question 25

When you do parent-offspring regression what is part of the differences seen between parent and offspring caused by

Answer 25

dominant, recessive, and additive genetic differences

Question 26

How to calculate narrow sense heritability?

Answer 26

H^2=VA/VA + VD + VI + VE VA= additive variation VD=dominance variation VI=epistatic variation