Ch. 13, 14

Physical attribute (hair color)

Section of DNA that code for a specific trait AGCGTTTACT = red hair (phenotype)

DNA wrapped around histones

Different forms of a gene R: red allele r: gray allele

Genotype: Rr Phenotype: red hair

Let’s do some science!

In rabbits long ears are dominant to floppy ears. If a purebred long eared rabbit mates with a hybrid rabbit, what is the probability a bunny will be a hybrid?

Observing two traits in one cross

P-generation gametes: Purebred: round RR yellow YY Purebred: green rr wrinkled yy Resulting F1-generation?

P-generation gametes: Purebred: round RR yellow YY Purebred: green rr wrinkled yy Resulting F1-generation Hybrid Round Rr and Yellow Yy Resulting F2-generation?

F1-generation gametes (RrYy X RrYy) Resulting F2-generation All pea styles

The inheritance of one gene does not influence inheritance of another

In cats Brown hair (B) is dominant to white hair (b) AND short tail (S) is dominant to long tail (s) cross a purebred short tailed, white cat with a purebred brown, long tailed cat

In cats Brown hair (B) is dominant to white hair (b) AND short tail (S) is dominant to long tail (s) Parents: SSbb X ssBB FOIL:

In cats Brown hair (B) is dominant to white hair (b) AND short tail (S) is dominant to long tail (s) F1: Hybrid for both traits SsBb F2 generation??????

In cats Brown hair (B) is dominant to white hair (b) AND short tail (S) is dominant to long tail (s) F2 Generation 9 brown and short tail 3 white and short tail 3 brown and long tail 1 white and long tail

Life is complex

F1 hybrids have an intermediate appearance Ex: Snapdragons red x white 

F1 hybrids have an intermediate appearance Ex: Snapdragons red x white  pink Key RR - red RW - pink WW - white

Both alleles are expressed dominantly Neither allele is recessive Ex: Roan horses red x white 

Both alleles are expressed dominantly Neither allele is recessive Ex: Roan horses red x white  Red and White Key RR - red RW - roan WW - white

More than two alleles are present for one trait Ex: Blood Groups A is dominant over O B is dominant over O A & B are codominant

More than two alleles are present for one trait Ex: Blood Groups A is dominant over O B is dominant over O A & B are codominant Key AA & AO: type A BB & BO: type B AB: type AB OO: type O

Traits that are associated with the X chromosome Ex: Red-green colorblindness

Traits that are associated with the X chromosome Ex: Red-green colorblindness Key: X C X C : female normal X C X c : female carrier X c X c : female colorblind X C Y: male normal X c Y: male colorblind

Multiple genes affect one trait Gene 1 codes for brown or black mice Gene 2 codes for pigment in general

One gene affects multiple traits Ex: Cats with blue eyes are deaf

A continuum of one trait is affected by multiple genes Ex: human skin color Three separate genes code for 7 shades of skin color