Co-Dominant and Sex-Linked Traits NOTES

I. Co-Dominant Genetic Traits All alleles for a trait are DOMINANT and both appear in offspring Different capital letters are used for each allele (Ex: Red = R, White = W) Two Options: 1.Traits BLEND. RedWhite Example: Red (RR) and White (WW) combine to make a PINK flower (RW)

2. Both traits show up individually. White Example: Black cow (BB) x White cow (WW) = Black and White spots (BW)

Practice: Long fur (L) in rats is codominant with short fur (S). Cross a medium fur mother with a long fur father. What is the probability of each phenotype for the offspring from this cross? 1. Start by making a geno-pheno key 2. Make your Punnett square cross 3. Determine the phenotypes of the offspring

II. Blood Types Co-Dominant trait with many alleles (A, B, and O) A and B = Dominant o = Recessive

If you are Blood Type A, you have “A” antigens, a type of protein, on the outside of your red blood cells. Antigens identify cells as “good” or “bad” to the body.

% Blood Types in the U.S.A.

BLOOD TYPE (phenotype) GENOTYPES Type AAA, Ao Type BBB, Bo Type ABAB Type Ooo Draw Table.

Cross a mother who is blood type AB with a father who is blood type O. What are the possible phenotypes for the offspring and what is the probability of each?

III. Sex Linked Traits Traits that are located on the X or Y chromosome If the trait is “A” or “a” and on the X chromosome, it is written as: X A X a or X A Y If on the Y chromosome, only males can have that trait (XY A )

Sex Chromosomes

H = no hemophilia ; h = hemophilia

Color Blindness X-linked, recessive trait

What is the probability of a colorblind child?