Download Simple Genetic Practice Problems

Simple Genetics Practice Problems
Name
Period
1. For each genotype, indicate whether it is heterozygous (HE) or homozygous (HO) dominant (D) or recessive (R).
Heterozygous will not be dominant or recessive.
AA HO D
Bb HE
Cc
ff
GG
Dd
HH
Pp
nn
2. For each of the genotypes below, determine the phenotype.
Purple flowers are dominant to white flowers
PP __Purple ___________________
Pp ___Purple__________________
pp __white__________________
Brown eyes are dominant to blue eyes
BB ___________________________
Bb ___________________________
bb ___________________________
Round seeds are dominant to wrinkled
RR ___________________________
Rr ___________________________
rr ___________________________
Bobtails are recessive (long tails dominant)
TT ___________________________
Tt ___________________________
tt ___________________________
3. For each phenotype, list the genotypes. (Remember to use the letter of the dominant trait)
Straight hair is dominant to curly.
____________ straight
____________ straight
____________ curly
Pointed heads are dominant to round heads.
____________ pointed
____________ pointed
____________ round
Practice crosses – show all work!
4. Set up the square for each of the crosses listed below. The trait studied is round seeds (dominant) and wrinkled seeds
(recessive). Do a and b for the round seed and wrinkled seed trait.
a. A plant with that is homozygous dominant for round seeds crossed with a heterozygous plant for seed shape. Show
the cross in a Punnett Square. List the genotypic and phenotypic ratios beside the Punnett square.
b. Cross two heterozygous for seed type. Show the cross using a Punnett Square. List the genotypic and phenotypic
ratios for this cross.
5. A tall plant allele is dominant to a short plant allele for plant height. A pea plant that is homozygous dominant for
height is crossed with a plant homozygous recessive plant for height. List the type of alleles that can be inherited?
Set up a Punnett square the show the cross. What are the genotypic
ratios? What are the phenotypic ratios?
6. Purple flowers show complete dominance to white flower plants. White flowers are recessive to purple flowers with
a complete dominance inheritance patterns. A. Show the Punnett Square for a white flowered plant crossed with a
plant heterozygous for the trait. What are the genotypic ratios? What are the phenotypic ratios? B. Two plants, both
heterozygous for the gene that controls flower color are crossed. What percentage of their offspring will have purple
flowers? ______________ What percentage will have white flowers? ___________
8. In guinea pigs, the allele for short hair is dominant. What genotype would a heterozygous shorthaired guinea pig
have? _______What genotype would a purebreeding, short-haired guinea pig have? _______What genotype would a
longhaired guinea pig have? ________
Below use different letters to represent alleles to show incomplete or codominance.
10. White flowers and Red flowers show a pattern of incomplete dominance. A homozygous red flower (RR) is crossed
with a homozygous white flower (WW). What is the genotypic ratio? What is the phenotypic ratio. Show the Punnett
square.
b. The heterozygous offspring of the above cross are crossed. What are the genotypic ratios? What are the phenotypic
ratios?
12. a. Chickens often show codominance for feather color. A. A homozygous black chicken (BB) is crossed with a
homozygous white chicken (WW). What is the genotypic ratio of the offspring? What is the phenotypic ratio of the
offspring? b. Show the Punnett Square for a heterozygous offspring with a chicken homozygous for black feathers.
Show the cross. What is the genotypic ratio? What is the phenotypic ratio?