Textbook Notes (270,000)
US (100,000)
BU (1,000)
CAS BI (200)
Chapter 3

CAS BI 206 Chapter Notes - Chapter 3: Penetrance, Allele Frequency, Epistasis


Department
Biology
Course Code
CAS BI 206
Professor
Chip Celenza
Chapter
3

This preview shows half of the first page. to view the full 2 pages of the document.
Chapter 3: Extensions to Mendel’s Laws
Extensions to Single-Gene Inheritance
Multifactorial traits affected by 2+ genes
Dominance is not always complete (ie, offspring will not always be A or a, they can be a mix
between)
Incomplete dominance offspring
phenotype does not resemble
either true-breeding parent
Neither allele is
recessive/dominant to
each other display
intermediate of two
phenotypes
Have exact phenotypic &
genotypic ratios (1:2:1)
Each allele different
version of protein each functional one works in tandem with other
Codominance both traits of true-breeding parents show up equally in heterozygote phenotype
Alleles aren’t always dominant/recessive D/R relationship is on an allele-allele basis
Dominance series listing of alleles from most dominant recessive (made of > and =)
Mutations new alleles
Allele frequency % of certain allele occurrence
Wild-type allele most common allele in population (W+)
Mutant allele rare allele in population
Monomorphic gene with only one common wild-type allele
Polymorphic gene with more than one common wild-type allele
Pleiotropy single allele determining multiple distinct characteristics (protein has cascade of
effects)
May be dominant/recessive/incompletely dominant/etc for different characteristics
Recessive lethal gene gene may be dominant for one trait but is recessive for lethality (3:1 ratio
from Aa parents)
Extensions to Multifactorial Inheritance
Genotypic classes phenotypes defined in terms of absence or presence of dominant alleles of 2
genes
Complete dominance both D (A-B-); One (A-bb); other (aaB-); neither (aabb)
Incomplete dominance/codominance give rise to more than 4 phenotypes
Complementary gene action aaBB x AAbb same phenotype (at least one dominant allele of
each required for phenotype)
Epistasis the effects of one gene’s alleles (epistatic) hides the effects of another gene’s alleles
(hypostatic)
You're Reading a Preview

Unlock to view full version