chapter 7 - complex traits

Question 1

mendelian traits

Answer 1

caused by a single gene

Question 2

polygenic traits

Answer 2

caused by multiple genes

Question 3

polygenic trait examples

Answer 3

height, skin color, body weight, illnesses, etc

Question 4

single gene traits often produce an _______ effect

Answer 4

all or none

Question 5

polygenic traits produce a continuously _____ phenotype

Answer 5

varying

Question 6

polygenic traits can also be called ______ traits

Answer 6

quantitative

Question 7

Quantitative Trait Loci

Answer 7

QTL’s; name for DNA sequences

Question 8

frequency of distribution of phenotypes forms a __________ curve

Answer 8

bell-shaped

Question 9

empiric risk

Answer 9

used to predict the chance that a polygenic complex trait will occur in an individual based on familial relationship; uses the incidence of the characteristic in a specific population

Question 10

incidence

Answer 10

rate at which a certain event occurs

Question 11

prevalence

Answer 11

proportion/number of individuals who have a particular trait at a specific time

Question 12

empiric risk is not a calculation, but a ….

Answer 12

population statistic based on observation

Question 13

empiric risk increases with 3 things:

Answer 13

1) severity of disease
2) number of affected family members
3) how closely related a person is to affected persons

Question 14

heritability

Answer 14

estimates the proportion of variation in a complex trait due to genetics in a particular population at a certain time; refers to the degree of variation in a trait due to genetics, and not to the proportion of the trait itself attributed to genes

Question 15

heritability equals ____ for a trait whose variability is completely the result of gene action

Answer 15

1.0

Question 16

broad-sense heritability

Answer 16

H^2

Question 17

sibling to sibling % shared genes (coefficient of relatedness)

Answer 17

50%

Question 18

parent to child % shared genes (coefficient of relatedness)

Answer 18

50%

Question 19

uncle/aunt to niece/nephew % shared genes (coefficient of relatedness)

Answer 19

25%

Question 20

half-siblings % shared genes (coefficient of relatedness)

Answer 20

25%

Question 21

grandparent to grandchild % shared genes (coefficient of relatedness)

Answer 21

25%

Question 22

first cousin to first cousin % shared genes (coefficient of relatedness)

Answer 22

12.5%

Question 23

concordance

Answer 23

measures the frequency of expression of a trait in both members of monozygotic or dizygotic twins

Question 24

discordant

Answer 24

twins who differ in a trait

Question 25

dizygotic twins

Answer 25

shared environment % 50% of genes

Question 26

monozygotic twins

Answer 26

identical genotype and shared environmnet

Question 27

genome-wide association study (GWAS)

Answer 27

compares many genetic markers across the genome between 2 large groups of people, usually 1 with a particular trait/disease and 1 without it

Question 28

GWAS uses genetic markers, including SNP's and CNV's

Answer 28

single nucleotide polymorphisms, copy number variants

Question 29

single nucleotide polymorphism (SNP)

Answer 29

a site in the genome that has a different DNA base in >1% of a population

Question 30

copy number variation (CNV)

Answer 30

tandomly repeated DNA sequence

Question 31

to achieve statistical significance, a GWAS must include at least _____ markers

Answer 31

100,000

Question 32

study designs in GWAS

Answer 32

- cohort study - case-control study - affected sibling pair strategy - homozygosity mapping

Question 33

cohort study

Answer 33

researchers follow a large group of individuals over time and measure many aspects of their health

Question 34

case-control study

Answer 34

pairs of individuals are matched so that they share as many characteristics as possible

Question 35

affected sibling pair strategy

Answer 35

tests identify SNP's that siblings with the same condition share but that siblings who do not both have the condition do not share

Question 36

homozygosity mapping

Answer 36

disease-causing mutations are identified in homozygous genome regions that children inherit from parents who are related to each other

Question 37

limitations of GWAS

Answer 37

- so much data - prone to error - reveal associations between information, not causes - bias can be a part of it - accuracy is affected by complicating factors like phenocopy and epistasis - could miss rare SNP's

Question 38

body mass index BMI

Answer 38

weight (kg) / height2^2(m^2)

Question 39

leptin

Answer 39

protein hormone produced by fat cells - signals the hypothalamus to decrease appetite - acts in the long term to maintain weight

Question 40

ghrelin

Answer 40

peptide hormone produced in the stomach - responds to hunger by increasing appetite - functions in the short term to regulate weight