12.2 Alleles Can Produce Multiple Phenotypes

Question 1

Mutations

Answer 1

Mutations are stable, inherited changes in the genetic material, leading to new variations in the gene pool (new alleles).

Question 2

Wild Type

Answer 2

The wild type refers to the allele present in most of the population. Other alleles are considered mutant alleles. In plants or wild animals, if wild-type alleles are present less than 99% of the time, the gene is polymorphic.

Question 3

Multiple Alleles

Answer 3

Multiple alleles often show a hierarchy of dominance, with many different allele combinations for one trait. This means that traits are generally not based on just two alleles.

Question 4

Incomplete Dominance

Answer 4

In incomplete dominance, heterozygotes have intermediate phenotypes, showing a blend of the two traits.

Question 5

Codominance

Answer 5

In codominance, alleles produce phenotypes that are both present in the heterozygote. For example, the ABO blood group system has two codominant alleles: I^A, I^B, and recessive i.

Question 6

ABO Blood Group System

Answer 6

In the ABO blood group system, individuals with the A group make A antigen and anti-B antibodies, those with the B group make B antigen and anti-A antibodies, AB group individuals make both A and B antigens, and O group individuals have no antigen and anti-AB antibodies.

Question 7

Pleiotropy

Answer 7

Pleiotropy occurs when one allele has multiple phenotypic effects.

Question 8

Epistasis

Answer 8

Epistasis refers to the phenotypic expression of one gene being influenced by another gene.

Question 9

Hierarchy of Dominance

Answer 9

Multiple alleles often exhibit a hierarchy of dominance, where certain alleles are dominant over others in determining the phenotype.

Question 10

New Alleles in the Gene Pool

Answer 10

Mutations introduce new alleles into the gene pool, contributing to genetic diversity within a population. These new alleles may alter traits and affect the phenotype of individuals.