Question

1. In loppins (fictitious diploid invertebrates), ear shape is controlled by two genes with two alleles each; upright ears (F) is dominant to floppy ears (f), and double-pointed ears (P) is dominant to single-pointed ears (p). Moreover, due to genetic interactions, floppy ears are always single-pointed. A loppin with floppy ears is crossed to a loppin with upright single-pointed ears, and the phenotypic ratios in the offspring are 2 floppy : 1 double-pointed upright : 1 single-pointed upright. What are the genotypes of the parents?

a. P/p; f/f and p/p; F/f

b. p/p; f/f and p/p; F/f

c. P/p; F/f and p/p; F/f

d. P/p; f/f and p/p; F/F

2.

Two new mutant lines of a flowering plant have been obtained; one breeds true for blue flower color and the other breeds true for red flower color (wild-type flower color is purple). Consider the following crosses.

1. blue × purple= F₁ all purple F₂ 75% purple; 25% blue
2. red × purple = F₁ all purple F₂ 75% purple; 25% red
3. red × blue = F₁ all purple

If the red pigment is a precursor of the purple pigment, the blue pigment is a precursor of the red pigment, and a colorless compound is the precursor of the blue pigment in a linear biosynthetic pathway controlling flower color, what phenotypic ratios do you expect in the F₂ of cross 3?

a. 9 purple: 3 red: 3 blue: 1 colorless

b. 3 puprle: 1 white (colorless)

c. 12 purple: 3 blue: 1 white (colorless)

d. 9 purple: 4 blue: 3 red

3.

Haploinsufficiency

a. can be the cause of some autosomal dominant disorders.

b. is when there is not enough gene product to bring about a wild-type condition

c. is when there is not enough gene product to bring about a wild-type condition AND can be the cause of autosomal dominant disorders.

Thanks, sorry I'm running out of questions remaining!

Answer 1

1. A loppin with floppy ears = ff Pp
A loppin with upright single-pointed ears = Ff pp
Parental cross: ffPp X Ffpp
Gametes: (fP) (fp) X (Fp) (fp)
Progeny:
FfPp = Upright double-pointed ears
ffPp = Floppy ears
Ffpp = Upright single-pointed ears
ffpp = Floppy ears
Progeny phenotypic ratio = 1:2:1

2.
Blue = BB
Red = RR
Purple = PP
B R   
Colorless precursor --------> Blue --------> Red --------> Purple
Blue = bb
Red = rr
Purple = B_R_

Cross-I: blue × purple= F1 all purple; F2 75% purple; 25% blue
bbRR X BbRR
F1 = BbRR

Cross-II: red × purple = F1 all purple; F2 75% purple; 25% red
BBrr X BBRR
F1 = BBRr

Cross-II: red × blue = F1 all purple
BBrr X bbRR
F1 = BbRr
F2 phenotypic ratio = 9:3:4
9 = B_R_ = Purple
3 = bbR_ = Blue
3 = B_rr = red
1 = bbrr = Blue

3. Haploinsufficiency is when there is not enough gene product to bring about a wild-type condition.