1. Single Factor Punnett Squares
Grading Rubric:
Single Factor Punnett Squares
Worth 25 Points

2. Parents genotypes: Dd X Dd
1. In certain breeds of dogs, deafness is due to a recessive allele (d) of a particular gene, and normal hearing is due to its dominant allele (D). What is the expected outcome of a cross between two heterozygous dogs?
Parents genotypes: Dd X Dd
1 point
1 point D d
1 point DD Dd dd
1 point
Genotypic ratio = 1:2:1
Phenotypic ratio = 3:1 D
1 point d
5 points

3. Parents genotypes: Cc X Cc
2. In man, normal pigmentation is due to a dominant allele (C), and albinism to it’s recessive allele (c). What is the expected outcome between a cross of a normal man and a normal woman if one of the children is an albino?
Parents genotypes: Cc X Cc
1 point
1 point C c
1 point CC Cc cc
1 point
Genotypic ratio = 1:2:1
Phenotypic ratio = 3:1 C
1 point c
5 points

4. Parents genotypes: bb X bb
3. In minks, brown is dominant over silver-blue color. What offspring would you predict if you crossed a two silver-blue minks?
Parents genotypes: bb X bb
1 point
1 point b b
1 point bb
1 point
Genotypic ratio = 0:4
Phenotypic ratio = 0:4 b
1 point b
5 points

5. Parents genotypes: RR X Rr
4. In snapdragons, red is not completely dominant over white flowers. What color flowers would you expect when you cross a red flower with a pink flower?
Parents genotypes: RR X Rr
1 point
1 point R R
1 point RR Rr
1 point
Genotypic ratio = 1:1
Phenotypic ratio = 1:1 R
1 point r
5 points

6. Parents genotypes: WW X BB
5. In chickens, white feather and black feathers are co-dominant. What is the expected outcome between a cross of a white and black chicken?
Parents genotypes: WW X BB
1 point
1 point W W
1 point WB
1 point
Genotypic ratio = 4:0
Phenotypic ratio = 4:0 B
1 point B
5 points

7. Total Points = 25 
5 points