Chapter 28

Question 1

What is quantitative genetics?

Answer 1

The study of traits that can be described numerically
Usually controlled by more than one gene

Question 2

What is a quantitative trait?

Answer 2

Any trait that varies measurably in a given species such as height, speed, mating calls, and diseases

Question 3

What are discontinuous traits?

Answer 3

Traits that fall into discrete categories or alleles that govern these traits that affect the phenotype in a qualitative way such as eye color and fur length

Question 4

What is an alternative way to describe discrete categories of quantitative traits?

Answer 4

A frequency distribution

Question 5

What is variance?

Answer 5

A common way to evaluate variation within a population

Question 6

Why are variances additive under certain conditions?

Answer 6

Variances of factors that contribute to a quantitative trait can be added to predict the total variance for that trait

Question 7

What is the name for the square root of the variance?

Answer 7

Standard variation

Question 8

What is the formula for mean?

Answer 8

Mean (X) = sum of all values in group (each value is multiple by its frequency) / number of individuals in the group

Question 9

What is the formula for variance?

Answer 9

Variance (Vx) = sum of the difference between each value and the mean / number of observations - 1

Question 10

What is the formula for standard variation?

Answer 10

SD = square root variance

Question 11

What is covariance?

Answer 11

The degree of variation between two variables within a group

Question 12

What is the formula for covariance?

Answer 12

Covariance (CoV) = sum (one variable - mean of group) x (one variable - mean value of other group) /. Total number of pairs of observations - 1

Question 13

What is the correlation coefficient (r)?

Answer 13

The strength of association between two variables
Ranges between +1 and -1

Question 14

If r>0, then …

Answer 14

One factor increases and the other factor increases

Question 15

If r=0, then …

Answer 15

Two factors are not related

Question 16

If r<0, then …

Answer 16

One factor increases, the other factor decreases

Question 17

What is the formula of the correlation coefficient?

Answer 17

Correlation coefficient (r) = CoV of X and Y / SD of X x SD of Y

Question 18

The significance of the correlation coefficient is directly related to?

Answer 18

Sample size and degrees of freedom

Question 19

What is polygenic inheritance?

Answer 19

The transmission of traits that are governed by two or more genes

Question 20

What are quantitative trait loci (QTLs)?

Answer 20

Locations of chromosomes that affect the outcome of quantitative traits

Question 21

Why are polygenic traits difficult or impossible to categorize into several discrete genotyping categories?

Answer 21

The number of genes controlling the trait increases and the influence of the environment increases

Question 22

What does it mean to backcross F1 offspring?

Answer 22

Cross two strains that differ in genetic markers and in the quantitative trait of interest

Question 23

What is heritability?

Answer 23

The amount of phenotypic variation within a group of individuals that is due to genetic variation

Question 24

If heritability has a value of 1, then …

Answer 24

All phenotypic variation in a group was due to genetic variation

Question 25

If heritability has a value of 0, then …

Answer 25

All the phenotypic variation was due to environmental factors

Question 26

What is the formula for phenotypic variance?

Answer 26

Vt = variance due to genetics (Vg) + variance due to environment (Ve)

Question 27

What does monomorphic mean?

Answer 27

All members of a population are homozygous for the same allele of a given gene, usually occurs through inbreeding

Question 28

What is genotype-environment association?

Answer 28

When certain genotypes are preferentially found in a particular environment

Question 29

What is the formula for broad sense heritability (hB2)?

Answer 29

HB2 = Vg / Vt

Question 30

What are the three different genetic categories that subdivides Vg?

Answer 30

Vg = variance due to additive effects of alleles (Va) + variance due to alleles that follow a dom/rec pattern of inheritance (Vd) + variance due to effects of alleles that interact in an epistatic manner (Vi)

Question 31

What is the formula for narrow sense heritability (hN2)?

Answer 31

HN2 = Va / Vt or hN2 = r observed / r expected

Question 32

What are the three distinctions of human fingerprints?

Answer 32

Arch, loop, or whorl

Question 33

What is a triradius?

Answer 33

Presence of the number of triple junctions

Question 34

How many triradius does arch have?

Answer 34

Zero

Question 35

How many triradius does loop have?

Answer 35

One

Question 36

How many triradius does whorl have?

Answer 36

Two

Question 37

What is heritability a widely misunderstood concept?

Answer 37

It describes the amount of phenotypic variation due to genetic variation for a particular population raised in a particular environment

Question 38

What is selection limit?

Answer 38

When after many generations the population eventually becomes monomorphic for all or most of the desirable alleles and selective breeding will not have an effect

Question 39

What is the formula for narrow sense heritability in response to selection.

Answer 39

HN2 = mean of offspring - mean of starting population / mean of parents - mean of starting population