Chapter 12.2.1 (Exam 3) Mutations Flashcards
Alleles Can Produce Multiple Phenotypes
How do new alleles arise?
Mutations
What are mutations?
Stable, inherited changes in the genetic material
What are wild-type alleles?
Allele present in most of the population
Other alleles are mutant alleles
What does it mean if a gene is polymorphic?
If the wild-type allele is present less than 99% of the time, the gene is said to be polymorphic
If there are more than one common allele than it is considered polymorphic
Any one individual has two alleles at a locus, but there may be many alleles in a population. What is one example of this?
Coat color in rabbits is determined by multiple alleles of the C gene
(Photographs show combinations of alleles that result in varying coat colors)
What is incomplete dominance?
Alleles are neither dominant nor recessive—heterozygotes have intermediate phenotypes and appear “blended”
In the F2 generation, the original phenotypes reappear; the alleles have not “blended”
What is codominance?
Alleles produce phenotypes that are both present in the heterozygote
What is one example of codominance?
ABO blood group system: Three different alleles encode an enzyme that adds specific groups to oligosaccharides that act as antigens on red blood cells
The three alleles, IA, IB, and IO produce different versions of the enzyme
What are the possible genotypes for type A blood? Type B? Type AB? Type O?
(IA, IA) or (IA, i)
(IB, IB) or (IB, i)
(IA, IB)
(i, i)
What does it mean if an allele is pleiotropic?
one allele has multiple phenotypic effects
What is one example of pleiotropism?
Phenylketonuria results from a mutation in the gene for a liver enzyme that converts phenylalanine to tyrosine
Phenylalanine builds up to toxic levels, which affects development in many ways
