Maury
Woman has two children, children are not albino
Husband is albino (aa, homozygous recessive)
Woman (could be heterozygous, Aa;
homozygous. AA)
If the husband is really their father, the children
must be heterozygous.
If the woman is homozygous dominant, what is the
chance that her children with her husband will be
albino? Zero percent chance of albino phenotype.
If she’s a carrier of albinism, what is the chance
that a child of the couple will be albino?
50%
Complete dominance
Monohybrid Cross
Segregation of alleles
Dihybrid cross
Independent Assortment
Pea purple, tall
x white, short
Codominance more than one dominant allele
Blood type two dominant alleles, a recessive
allele
A(d), B(d), O
Genotype AA Phenotype Blood type A
Genotype
Genotype
Phenotype
AA
A
AO
A
AB
AB
BB
OO
B
O
Incomplete Dominance
One dominant allele, one recessive allele
One dominant produces a weaker phenotypic
effect
Homozygous dominant full effect red flower
Heterozygous partial effect
pink flower
Homozygous recessive
white flower
Epistasis: One gene controls expression of another
gene
Pleiotropy: one gene has multiple effects
Exceptions to independent assortment:
Linked Genes: genes that are on the same
chromosome
Purple Tall and White Short parental
phentypes
Purple short and White Tall recombinant
phenotype
With unlinked genes, parental genotypes and
recombinant genotypes are equally likely
50% of either kind of genotype
With linked genes, recombinant genotyopes are
less likely
Probability of a recombinant genotype varies
depending on how close on the chromosome the
two genes are
Probability of recombination varies from 0% to
50%, depending on how far apart the two gene
loci are
Genes and environment: nature and nurture
Genes interact with the environment
Polygenic inheritance: multiple genes control one
trait, result in a spectrum or continuum of
phenotypes (quantitative traits)