Question

You are in charge of the national Unicorn breeding program. Unicorns can have either swirled or solid horns with the swirled (Sw) phenotype being dominant over solid (sw). Their fur can be gold (F⁺), bronze (f^b), silver (f^s) or white (f^w), with the colour alleles following a dominance series of: F⁺ > f^b > f^s > f^w

^{question 1}

a) Which pair could you mate to potentially get some offspring with silver fur and swirled horns?

Select one:

a. A bronze and swirled horned unicorn with a white and solid horned unicorn

b. A true breeding gold and swirled horned unicorn with a true breeding white and solid horned unicorn

c. A silver and solid horned unicorn with a silver and solid horned unicorn

b) You mate a silver fur, solid horned unicorn, whose mother had white fur and a swirled horn, with a white fur, solid horned unicorn whose mother had gold fur and a solid horn.  What is the probability that the offspring will have white fur (with any type of horn)?

Select one:

a. 1/16

b. 1/3

c. 1/4

d. 1/2

question 2

Merfolk have three pairs of autosomes and one sex chromosome; males are X0 and females are XX.

In merfolk the genes controlling tail fin shape and scale colour are on different autosomes. Solid tail fin (Ff) is dominant to forked tail fin (ff), and the F allele is recessive lethal. There are two alleles of the scale colour gene – C^B(blue) and C^R (red)– C^B and C^R show incomplete dominance with heterozygotes being purple.

The silent trait is X-linked and dominant (X^S) to normal voice (X⁺).

Atolla is a male merfolk, he has a forked tail fin, blue scales, and is voiceless (silent). Brachy is a female merfolk with a solid tail fin, purple scales and a normal voice.

a) What is the probability that a female child of a mating between Brachy and Atolla will be silent (it doesn't matter what tail shape or scale colour the child has)?

Select one:

a. 1/4

b. 0

c. 1/2

d. 3/4

e. 1

b) What is the probability that a mating between Brachy and Atolla would produce a child with a forked tail and purple scales (doesn’t matter whether they are silent or not)?

Select one:

a. 3/4

b. 1/3

c. 1/4

d. 2/3

e. 1/2

c) You mate a female merfolk with blue scales who is heterozygote for silent and a carrier of forked tail, to a silent male with blue scales who is also a carrier of forked tail. Which of the following are TRUE statements (you can choose more than one)

For this question ignore the phenotypes that are unmentioned. For example "a blue female" is a blue female who can be any colour, and either be silent or normal.

Select one or more:

a. This mating can produce silent or normal voiced offspring

b. This mating can produce silent or normal voiced female offspring

c. The probability of a female offspring having a forked tail and blue scales is 1/3

d. The probability of an offspring from this mating having a forked tail and normal voice is 1/6

Answer 1

1. a)

The correct answer is the option a - A bronze and swirled horned unicorn with a white and solid horned unicorn

Let the Genotype of bronze and swirled horned unicorn be fbfs/SwSw (since bronze is dominant than silver)

Genotype of the white and solid horned unicorn: fwfw/swsw (Both the alleles are recessive)

Parents: fbfs/SwSw ( Bronze and swirled )* fwfw/swsw (white and solid)

gametes of parent 1: fbSw, fsSw

gametes of parent 2: fwsw

offspring: fbfw/Swsw (bronze and swirled), fsfw/Swsw (silver and swirled)

therefore the correct answer is option a

The genotype of a true-breeding Gold and swirled unicorn is F+F+/SwSw and the genotype of a true-breeding white and solid unicorn is fwfw/swsw. So there is no chance to produce a unicorn with silver fur. Hence option b is incorrect

The allele for solid horn is recessive, so to exhibit the phenotype, two recessive alleles must be present. So Two unicorns with solid horns will not produce a unicorn with swirled horns. Hence option c is incorrect

1. b)

The answer is option d - 1/2

Genotype of silver fur and solid horned = fsfw/swsw (since the mother has white fur)

Genotype of white fur and solid horned = fwfw/swsw

Parents : fsfw/swsw * fwfw/swsw

gametes of parent 1: fs/sw, fw/sw

gametes of parent 2: fw/sw

offspring : fsfs/swsw (silver and solid), fwfw/swsw (white and solid)

progeny percentage of phenotype white fur: 50%

the probability that the offspring will have white fur = 1/2

Hence answer is option d

2. a)

The answer is option c - 1/2

Atola (male) is voiceless and Brachy (female) has a normal voice

Parents: X+X+ (normal voice female ) * XSO (silent male)

gametes of male: XS, O

gametes of female: X+

offspring: XSX+ (silent female), X+O (normal voice male)

phenotypic ratio: 1:1

Progeny percentage of silent female - 50%

hence the answer is option c - 1/2

2. b)

The answer is option c -1/4

Atolla has forked tail fin and blue scales and Brachy has a solid tail fin and purple scales

Genotype of forked tail fin and blue scales: ff/CBCB

genotype of solid tail fin and purple scales: Ff/CBCR

gametes of parent 1: f/CB

gametes of parent 2: F/CB, F/CR, f/CB, f/CR

offspring: Ff/CBCB (solid, blue), Ff/CBCR (solid,purple), ff/CBCB (forked,blue), ff/CBCR (forked, purple)

Phenotypic ratio- 1:1:1:1

Progeny percentage of phenotype forked tail and purple scales: 25%

Hence the answer is option c - 1/4

2. c)

The correct answer is option a

Genotype of female parent: XSX+/Ff/CBCB

genotype of male parent: XSO/Ff/CBCB

gametes of female parent : XS/F/CB, XS/f/CB, X+/F/CB, X+/f/CB

gametes of male parent: XS/F/CB, XS/f/CB, O/F/CB, O/f/CB

offspring: XSXS/FF/CB_, XSXS/Ff/CB_, XSO/FF/CB_, XSO/Ff/CB_, XSXS/Ff/CB_, XSXS/ff/CB_, XSO/Ff/CB_, XSO/ff/CB_, XSX+/FF/CB_, XSX+/Ff/CB_, X+O/FF/CB_, X+O/Ff/CB_, XSX+/Ff/CB_, XSX+/ff/CB_, X+O/Ff/CB_, X+O/ff/CB_

Phenotypic ratio of offspring with a forked tail and normal voice: 1/16. so option d is incorrect

Out of 8 female offspring, two female have forked tail and blue scales - so option c is incorrect

All female offspring are silent. So option b is incorrect