Question

1) One parent has yellow flowers, which is the dominant allele Y. The second parent has white flowers, the recessive allele y. If the offspring are all yellow, what is the genotype of each parent?

2) A plant is homozygous for the recessive gene "a" causing the plant to be short.

What is the genotype and the phenotype of this plant? (In your answer, be very clear about which is the genotype and which is the phenotype).

3) The allele for brown fur in mice (B) is dominant to the allele for white fur (b). What type of offspring would you expect if you crossed a heterozygous brown mouse with a homozygous white mouse?

a) 75% white and 25% brown

b) 75% brown and 25% white

c) 100% brown

d) 50% brown and 50% white

4) An example of alleles is:

		TT and Tt
		AB and Tt
		X and Y
		T and t

5) An extra finger in humans is rare but is due to a dominant gene. When one parent is normal and the other parent has an extra finger but is heterozygous for the trait, what is the probability that the first child will be normal?

0%

25%

50%

75%

6)

What does a Punnett square show?

only the dominant alleles in a genetic cross

all of Mendel’s discoveries about genetic crosses

only the recessive alleles in a genetic cross

all the possible outcomes of a genetic cross

7)

If the allele for brown hair is represented as "B," it would mean that __________.

		brown hair is a dominant trait
		the gene for brown hair is carried on the maternal chromosome
		brown hair is a recessive trait
		the gene for brown hair is carried on the paternal chromosome Thank You!

Answer 1

1. Yellow × white = yellow

All the progeny the yellow in colour. It mean yellow is dominant over white. It also means that both of the parents were homozygous for their respective genotypes.

Yellow parent = YY

White parent = yy

Yellow progeny = YY × yy = Yy

2. Because the trait is recessive, the genotype of the plant must be homozygous.

Plant will be short with genotype aa.

3. Brown = BB or Bb

White = bb

Bb × bb

Gametes	b
B	Bb brown
b	bb white

White mouse = 1/2 = 50%

Brown mouse = 1/2 = 50%

Option D

4. T and t

Alleles are in single letter and genotypes are in double letter for a gene.

X and Y are chromosomes.

According to guidelines, only first question can be answered. Please give a good rating.