In guinea pigs, rough coats (with lots of swirly cowlicks) are dominant over smooth coats. If a male homozygous dominant guinea pig is crossed with a female heterozygous guinea pig, what are the possible genotypes and phenotypes of the offspring? Complete the Punnett square and the percentages of rough and smooth coated offspring.

Question

***Please follow all Punnett square rules to complete this question. (Letters and numbers, only)

Please use the following: Rough = R and Smooth = r


offspring 1 offspring 2
offspring 3 offspring 4

% rough

% smooth



Blank 1:
Blank 2:
Blank 3:
Blank 4:
Blank 5:
Blank 6:
Blank 7:
Blank 8:
Blank 9: % rough ___
Blank 10: % smooth ___

Answer 1

To complete this genetic cross, we will first identify the genotypes of the parent guinea pigs:

• The male guinea pig is homozygous dominant, so his genotype is RR.
• The female guinea pig is heterozygous, so her genotype is Rr.

Next, we will create a Punnett square to determine the possible genotypes of the offspring:

         R      R
      ----------------
   R |    RR   |   RR   |
      ----------------
   r |    Rr   |   Rr   |
      ----------------

The possible genotypes for the offspring are:

1. RR (from R and R)
2. RR (from R and R)
3. Rr (from R and r)
4. Rr (from R and r)

Now, we can summarize the offspring genotypes:

• 2 offspring are RR.
• 2 offspring are Rr.

Now we can determine the phenotypes:

• Both RR and Rr offspring (Rough) will display the rough coat phenotype since rough is dominant.

Thus, all offspring have a rough coat:

• % rough = 100%
• % smooth = 0%

Now, we will fill in the Blanks:

Blank 1: R
Blank 2: R
Blank 3: R
Blank 4: r
Blank 5: RR
Blank 6: RR
Blank 7: Rr
Blank 8: Rr
Blank 9: % rough 100
Blank 10: % smooth 0