study guide 6

Question 1

what are “quantitative/complex” traits

Answer 1

traits that can be described numerically and are controlled by more than one gene and are significantly influenced by the environment

Question 2

give an example of a quantitative trait

Answer 2

weight, height, metabolic rate

Question 3

why is it important to study quantitative traits

Answer 3

these traits are important for plant and animal breeders and many human diseases are also controlled by several genes. Additionally, many traits allow a species to adapt to its environemtn due to the quantitative traits

Question 4

whats the difference between continuous and discontinous traits

Answer 4

quantitative traits show a continuum of variation within a group so they are continous

Question 5

what does a frequency distribution graph look like

Answer 5

a normal distribution with the traits of interest varying symmetrically around the mean.

Question 6

if a frequency distribution graph has a wider base, wht does this mean

Answer 6

it means that the population has more variation

Question 7

what is heritibility

Answer 7

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

Question 8

what is the difference between broad sense and narrow sense heritibility

Answer 8

broad sense heritibility is a measure of the phenotypic variation due to the total genetic variation

narrow sense heritibility is a meausre of phenotypic variation due to the additive effect of alleles

Question 9

why do we measure narrow sense heritibility

Answer 9

it only focuses on the additive effects of alleles as the allelic variations due to dominant/recessive patterns and epistatic interactions is difficult to measure

Question 10

how do we measure broad sense heritability based on the results of a clonal transplant experiment

Answer 10

the variation due to genetics is 0, zo the total variation is equal to the variation from the environment, this can be used to find the VG for the heterogenous populations and used to calculate the heritability Vg/VP

Question 11

what does a broad sense heritability y value of 1 mean

Answer 11

it means all variation is due to genetics

Question 12

what does a broad sense heritability value of 0 mean

Answer 12

all variation is due to the environment

Question 13

what does the correlation coefficient (r) measure

Answer 13

it measures how well the variation in one group can predict the variation in another group

Question 14

what does a correlation coefficent of 1 or -1 indicate?

Answer 14

a coefficient of 1 indicates a positive linear relationship (as one goes up the other goes up)

a coefficient of -1 indicates a negative linear relationship (as one downs up the other goes down)

Question 15

how is the correlation coefficient used to measure narrow sense heritability

Answer 15

r observed/ r expected

Question 16

what does it mean if the narrow sense heritability is close to 1?

Answer 16

it means a majority of the variation is due to the additive effects of alleles

Question 17

what are we assuming when we measure narrow sense heritability

Answer 17

we assume that the majority of genetic variation in the population is due to alleles that have additive effects

Question 18

what is measured by the correlation coefficient

Answer 18

the degree to which the variation in one group predicts the variation in another

Question 19

what is the expected phenotypic correlation value between parent-offspring, assuming that variation is due to genetics alone

Answer 19

the expected correlation is 0.5 since offspring inherit 1/2 of their DNA/ alleles from their parents

Question 20

if the narrow sense heritability is close to one, what does this mean

Answer 20

it means that a majority of the variation is due to the additive effect of alleles

Question 21

how is linear regression analysis between parent-offspring used to estimate narrow sense heritability

Answer 21

the slope of the line

Question 22

what does linear regression show

Answer 22

it shows the relationship between variables and whether or not a change in x results in a change in y (dependent variable)

Question 23

what does the slope of the line tell us

Answer 23

it tells us the expected proportion of the offsprings trait value that can be explained by the genetic factors passed down from their parents

Question 24

how is the correlation coefficient different from the slope of a linear regression line

Answer 24

the correlation coefficient measures the strength and direction of the relationship between two variable and it is a unitless measurement

the slope of the regression line indicates the average change in the dependent variable for a one-unit change in the independent variable

it is scaled to the units of the variables

Question 25

which is a unitless measurement? the correlation coefficient or slope?

Answer 25

the correlation coefficient the slope is scaled to the units of the variables

Question 26

if the slope is close to one, what does this tell us about the heritability and predictability?

Answer 26

it tells us the variation is due to the additive effects of alleles and that the independent variable (ex. parent height) is fairly predictive of the dependent variable (offspring height)

Question 27

if the slope between the parent and offspring height is 0.583, what does this tell us about the populations?

Answer 27

more than half of the variation is due to the additive effect of alleles, this means the height of the parent is fairly predictive of the height of the offspring but not entirely

Question 28

if the slope between student-friend height is 0.058, what does this tell us about the relationship

Answer 28

the variation is not due to genetic effects and the height of the student is not predictive of the height of their friends

Question 29

what are the assumptions of broad sense heritability

Answer 29

genes and environment are the only things that affect a trait these factors are independent of one another