Punnett Square practice
Put all answers on a separate sheet of paper
SIMPLE DOMINANT & RECESSIVE TRAITS
Let's say that in seals, the gene for the length of the whiskers has two alleles. The
dominant allele (W) codes long whiskers & the recessive allele (w) codes for short
whiskers.
1) What percentage of offspring would be expected to have short whiskers from the cross
of two long-whiskered seals, one parent is homozygous dominant and the other one is
heterozygous?
CODOMINANT TRAITS
In humans, wavy hair (CS) results by the co-dominant situation of curly hair (C) and
straight hair (S).
2) What are the possible phenotypes if a curly-haired man and wavy-haired woman have
children?
INCOMPLETE DOMINANCE
A cross between a blue blahblah bird (I made this bird up) & a white blahblah bird
produces offspring that are silver. The color of blahblah birds is determined by just two
alleles.
3.) What are the genotypes of the parent blahblah birds in the original cross?
4.) What is/are the genotype(s) of the silver offspring?
5.) What would be the phenotypic ratio of offspring produced by two silver blahblah
birds?
POLYGENIC INHERITANCE
Phenotype
B blood
A blood
AB blood
O blood
possible genotype
BB or BO
AA or AO
AB
OO
6.) Could a man with type B blood and a woman with type AB produce a child with type
O blood?
A test was done to determine the biological father of a child. The child's blood is Type A
and the mother's is B. Guy #1 has a blood type of O, & Guy #2 has blood type AB.
7.) Which guy is the biological father?
2 FACTOR CROSS
8.) In pigs, curly tails (C) are dominant over straight tails (c). Pink color (P) is dominant
over gray (p). You are to cross a male pig that is homozygous dominate for both traits
with a female pig that is homozygous recessive for type of tail and heterozygous for
body color. Set up a 2 factor punnett square for this cross:
CCPP x ccPp