Chapter 18

Question 1

Complex traits

Answer 1

Not a simple Mendelian inheritance but usually quantitative (measured) traits (NOT green vs yellow peas). Expression affected by environment and multiple genes. Ex: human height, milk production, grain yield.

Question 2

Inheritance on a trait influenced by 3 genes- seed color in wheat

Answer 2

Each of 3 genes = more red color when dominant allele is present. Number of dominant alleles determines seed color. Case of genetic determination of a trait. Most complex traits are influenced by genetic variation and the environment

Question 3

Different genotypes have a different response to environmental conditions

Answer 3

Corn strains: strain 1 better with low soil nitrogen while strain 2 better with high levels. Mice: low fat diet both mice remain thin, high fat diet only A becomes obese while B thin. Both genes and environment affect phenotype.

Question 4

Twins can provide a measure of effects of environment vs. genetics

Answer 4

Identical twins- from one attire that splits early in development, genetically identical. Fraternal twins- from 2 separate eggs fertilized by 2 separate sperm, no more identical than siblings

Question 5

Concordance

Answer 5

36 pairs of identical twins w/ both showing adult onset diabetes. 40 pairs w/ only one showing it. 336 w/ neither showing it. Concordance = 36/(36+40)= 47%. % both twins show trait from all pairs with atleast 1 twin showing trait.

Question 6

Difference in concordance between identical and fraternal twins shows…

Answer 6

Genotype

Question 7

Concordance of <100% in identical twins shows….

Answer 7

Effect of environment