lecture 10 mendelian genetics continued

Question 1

lethal alleles

Answer 1

2:1 ratio instead of 3:1 ratio

offspring with lethal allele doesn’t survive

Question 2

polymorphism

Answer 2

one gene can have many alleles

each individual can only have 2 alleles

Question 3

incomplete dominance

Answer 3

heterozygote possesses an intermediate phenotype

disproves blending inheritance may reappear

Question 4

co-dominance

Answer 4

both phenotypes exist side by side

e.g ABO blood antigen system

Question 5

epistasis

Answer 5

one gene affects the action of another

e.g gene B under epistatic control of gene A

Question 6

polygenic traits

Answer 6

controlled by many genes- additive affect

can be continuous or quantitative

Question 7

the environment

Answer 7

environment affects phenotype

can ‘smooth’ differences between phenotypes

Question 8

pleiotropy

Answer 8

one gene can have many affects

e.g sickle cell, coloration in siamese cats, drosophila many traits affected by one gene