Extensions of Mendelian Inheritance

Question 1

Incomplete Penetrance

Answer 1

A dominant allele does not influence the outcome of a trait in a heterozygote individual

Question 2

Expressivity

Answer 2

The degree to which a trait is expressed

Question 3

If 60% of heterozygotes carrying a dominant allele exhibit a trait ____

Answer 3

the trait is 60% penetrant

Question 4

Incomplete dominance

Answer 4

The heterozygote phenotype is intermediate between the homozygotes.

Question 5

Over-dominance (Heterozygous advantage)

Answer 5

The heterozygote for sickle cell has an advantage over the homozygous dominant and recessive.

Question 6

Type AB blood is an example of what?

Answer 6

Codominant

Question 7

Sex-linked traits

Answer 7

Traits are governed by genes on the sex chromosomes. Alleles are dominant in one sex and recessive in the opposite

Question 8

When are sex influenced visible?

Answer 8

Heterozygotes (Ss for males = scurs; Ss for females= no scurs)

Question 9

Are sex-influenced traits autosomal?

Answer 9

yes

Question 10

Sex-limited inheritance

Answer 10

Traits that only occurs in one of the sexes

Question 11

Lethal alleles

Answer 11

One that has the potential to cause the death of an organism

Question 12

Conditional lethal alleles

Answer 12

May kill an organism when certain environmental conditions prevail

Question 13

Agouti gene in mice?

Answer 13

Homozygous for agouti yellow allele = dead mice

Question 14

Dominant lethal

Answer 14

Huntingtons disease

Question 15

Recessive lethal

Answer 15

cystic fibrosis, manx cats, agouti gene mice

Question 16

Complementation

Answer 16

Same phenotype caused by mutations in different genes. Wild type offspring are produced from a cross between parents that both display the same recessive phenotype

Question 17

Epistasis

Answer 17

A gene can mask the phenotypic effects of another gene. Both parents have recessive phenotype, offspring has WT phenotype

Question 18

Gene modifier effect

Answer 18

Alleles of one gene modifies the phenotypic outcome of alleles of a different gene

Question 19

Gene redundancy

Answer 19

Existence of multiple genes that perform the same function. Loss of one gene does not change phenotype, loss of two genes changes phenotype