EXam2

monohybrid self cross genotypic ratio

1 homozygous dominant

2 heterozygous

1 homozygous recessive

monohybrid self cross phenotypic ratio

3 dominant

1 recessive

to find dominant allele

cross truebred x truebred

to find genotype

use testcross

test cross of monohybrid genotypic ratio

1 heterozygous

1 homozygous recessive

test cross of monohybrid phenotypic ratio

1 dominant 

1 recessive 

monohybrid self cross phenotypic ratio

3 dominant

1 recessive 

test cross of dihybrid genotypic ratio

1 both heterozygous dominant

1 A heterozygous dominant, B homozygous recessive

1 A homozygous recessive, B heterozygous dominant

1 both homozygous recessive

test cross of dihybrid phenotypic ratio

1 both dominant (A_ B_)

1 A dominant B recessive (A_ bb)

1 A recessive B dominant (aa B_)

1 both recessive (aa bb)

dihybrid self cross phenotypic ratio (complete dominance and independent assortment)

9 both dominant 

3 one dominant; one recessive

3 one recessive; one dominant 

1 both recessive

recessive epistasis phenotypic ratio

9:3:4

dominant epistasis phenotypic ratio

12:3:1

reciprocal recessive is also known as

complementary

reciprocal recessive/complementary phenotypic ratio

9:7

reciprocal dominant is also known as 

duplicate gene

reciprocal dominant/duplicate gene phenotypic ratio

15:1

complementation testing only works with

homozygous recessive mutants

cis vs trans conformation is about

dominant alleles

crossing over produces

different alleles on a sister chromatid

polymorphic traits

have multiple common allele variants there is no single “wild-type” allele

monomorphic traits

have single “wild type” allele. variant alleles are rare (<1%) and classified as “mutant

polygenic traits

influenced by multiple genes

pleiotropy

one gene affects multiple properties of an organism 

segregation

separation of two alleles into different gametes

independent assortment

alleles separate into gametes randomly with respect to alleles of other genes

allele

alternate form of a gene

gene

heritable entity that determines a characteristic

genotype of someone affected by autosomal recessive

must be homozygous

autosomal recessive affected person

got one allele from each parent, so their parents must also be affected or be carriers

unaffected by autosomal recessive 

could be homozygous WT or heterozygous carrier

autosomal recessive clue

unaffected individuals can have affected children

autosomal recessive pattern

can skip generations, rare*, becomes more common with inbreeding

tay-sachs disease

autosomal recessive disease that affects lysosome in neurons 

someone who doesn’t have autosomal dominant disease

must be homozygous recessive

parents of unaffected autosomal dominant

can be heterozygous (affected) or also unaffected homozygotes

someone affected by autosomal dominant

could be homzygous dominant or heterozygous 

autosomal dominant clue

affected individuals always have affected parent

autosomal dominant pattern

does not skip generations

huntigdon disease

autosomal dominant disease that causes shaking, personality changes, and death within 15 years, appears around age 40 

x-linked recessive sex more affected

males

x-linked recessive fathers

may have unaffected daughters

x-linked recessive sons

who have affected mothers will also be affected

x-linked recessive pattern

can skip generations via female carriers

x-linked dominant sex more affected

females

x-linked dominant affected fathers have

all affected daughters and no affected sons

x-linked dominant pattern

does not skip generations