BIO 102
Fall 2010
Genetics extra questions
1. Physically, what are alleles? Answer on your own
2. For each genotype, indicate whether it is heterozygous or homozygous
Aa
BB
KK
yy
Xx
Ans:
Hetero
hetero
3. For each of the genotypes below, determine the phenotype. 6 finger allele (T) is dominant to
5 finger allele (t)
TT
Tt
tt
Ans: 6 fingers
6 fingers
5 fingers
4. The purple flower allele (F) is dominant to the white flower allele (f). A white flowered plant is
crossed with a plant that is heterozygous for the trait.
Include a – d in your analysis.
a. The genotype and phenotype of each parent
b. The gametes that each plant makes – can show these in the Punnett square.
c. The genotypes AND phenotypes of the possible offspring
d. The percentage of the offspring expected to have PURPLE flowers.
Ans: a. ff X Ff (white X purple)
b. gametes = f and f
F and f
c. white (ff) or purple (Ff) d. 50%
5. Yellow seed allele (Y) is dominant. Green seed allele (y) is recessive. If a heterozygous pea
plant is allowed to self-pollinate, what proportion of offspring will also be heterozygous?
Ans: 50% heterozygous
6. In guinea pigs, short hair is dominant to long hair
Two short haired guinea pigs are mated several times. Out of
100 total offspring, 28 of them have long hair. What are the probable genotypes of the parents?
Show the cross. Ans: Rr X Rr
7. A woman with type A blood has a child with type O blood. She claims that man of blood Type
B is the father of her child. How would you respond to the following statements. Provide
details and/or show the cross that supports your statement.
a. The man claims: The mother's blood is type A, so the child's type O blood did not come
from him
b. The mother claims that further testing has shown that the man is heterozygous
Ans: a. man could be BO
b. supports that man is BO
8. The long fur of Persian cats is recessive to the short fur of Siamese cats (fur length gene), The
black fur of Persians is dominant to the brown and tan fur of Siamese (fur color gene). Mating
of a male black Persian with a female Siamese produces an f1 generation heterozygous for
both of these genes.
BIO 102
Fall 2010
Complete a Punnett square to show the expected genotypes and phenotypes of the offspring
from the mating of these f1 heterozygous cats. Use letters that enable you to easily
distinguish between the dominant and recessive alleles) Ans: 9:3:3:1 ratio of phenotypes:
black short, black tall, brown short, brown tall in that order)
9. In cows, the CR allele gives a red coat color, while the CW allele gives white. CR CW cows are
roan - they exhibit patches of red and white, Predict the phenotypic ratios of offspring when a
white cow is crossed with a roan bull. Ans: 50% red 50% roan. This is an advanced
problem will not be on exam.
10. OMIT not on exam The color of fruit for a certain plant is determined by two alleles. When two
plants with orange fruits are crossed, the following phenotypic ratios are present in the
offspring: 25% red fruit, 50% orange fruit, 25% yellow fruit.
a. What are genotypes of the parent orange-fruited plants? Use letter C for color gene.
b. What type of inheritance is occurring? (choose one)
Codominance
2 gene inheritance
Multiple alleles
Incomplete dominance
11. The ability to taste PTC, a bitter substance, is a dominant autosomal (not sex-linked) trait. A
man who can taste PTC has a mother who cannot taste PTC. The man’s wife cannot taste the
substance. What is the chance that their child will inherit the ability to taste PTC?
Answer: 50%