Question

In guinea pigs, the allele for short hair is dominant over long hair. If a heterozygous short hair guinea pig is crossed with another heterozygous short hair guinea pig, what is the probability of an offspring having long hair?

In pea plants purple flower allele is dominant to white flower alleles. If a homozygous purple flower plant is crossed with a white flower plant, what percent of their offspring would you expect to be purple?

Straight fur (S) is dominant over curly fur (s) in dogs and black fur (B) is dominant over brown fur (b). What is the genotype for a homozygous black dog with curly fur?

This is a sex-linked problem and as such you will need to think male versus female. Red-Green Colorblindness is an X-linked trait. If a woman who's father was color-blind but she is not marries a normal vision man, what chance to they have of their son being color blind? Give your answer in percentage of male offspring.

Answer 1

Answer 1: 1/4 probability

Explanation:

As we know allele for short hair is dominant over long hair

Lets allele for short hair = S ; allele for long hair = s

short hair guinea pig (heterozygous) = Ss

short hair guinea pig (heterozygous) (Ss) X   short hair guinea pig (heterozygous) (Ss)

	S	s
S	SS	Ss
s	Ss	ss

3:1 (three short hair : one long hair)

There is 1/4 probability of an offspring having long hair.

Answer 2: 100%

Explanation:

As we know purple flower allele is dominant to white flower alleles.

• Lets allele for purple flower = P ; allele for white flower = p
• Recessive trait expressed only when are in homozygous.

purple flower plant (homozygous) (PP)   X white flower plant (pp)

	P	P
p	Pp	Pp
p	Pp	Pp

100% of offspring expected to be purple.

Answer 3: Genotype for a homozygous black(B) dog with curly(s) fur is BBss.

Explanation:

As we know Straight fur (S) and black fur (B) alleles are dominant over curly fur (s) and brown fur (b) alleles.

Lets allele for Straight fur = S ; allele for curly fur = s ; allele for black fur = B ; allele for brown fur = b

Homozygous genotype means having two same types of allele.

So, genotype for a homozygous black(B) dog with curly(s) fur = BBss

Answer 4:

50% chances that they have of their son being color blind.

• If X = normal and X^c = colour-blind trait
• We know father was colour-blind and carry this trait (X^cY).
• So his daughter is phenotypically normal but genotypically carrier of this trait, (X^cX).
• Carrier daughter (X^cX) marries a colourblind man (X^cY)

	Xc	Y
Xc	Xc Xc	XcY
X	X Xc	XY

50% chances that they have of their son being color blind.