Download CoDominant and Sex Linked Trait Notes

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.
Example: Red (RR) and White (WW) combine
to make a PINK flower (RW)
2. Both traits show up individually.
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.
Draw Table.
BLOOD TYPE
(phenotype)
Type A
GENOTYPES
Type B
BB, Bo
Type AB
AB
Type O
oo
AA, Ao
• 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: XAXa or
XAY
• If on the Y chromosome, only males can
have that trait (XYA)
Sex Chromosomes
H = no hemophilia ; h = hemophilia
Color Blindness
• X-linked, recessive
trait
What is the probability of a
colorblind child?