A chart shows allele combinations for brown/blonde hair: Father’s Mother, Bb; Mother’s Mother, BB; Mother, Bb; Child, bb. What allele combinations are missing?

Question

Father’s Father
(brown hair)
  Father’s Mother
(brown hair)
Bb Mother’s Father
(blond hair)
  Father’s Mother
(brown hair)
BB
Father’s Father
(brown hair)
  Mother
(brown hair)
Bb
Child
(blond hair)
bb

Answer 1

To analyze the allele combinations in the chart you described, we should first summarize the genetic information:

1. Father’s Mother: Bb (brown hair)
2. Mother’s Mother: BB (brown hair)
3. Mother: Bb (brown hair)
4. Child: bb (blond hair)

Now, let’s address the missing allele combinations by noting the parental combinations necessary to produce a child with the genotype "bb."

Allele Combinations Based on Provided Information:

1. Father’s Father: Unknown (could be either BB or Bb, since the father must have at least one brown hair allele).
2. Mother’s Father: Unknown (not mentioned but could be either BB or Bb; however, we know he can't be bb since the Mother must have at least one brown hair allele).

Potential Pairings:

1. Father's Father (unknown) x Father's Mother (Bb):

   • Possible combinations:
     • BB x Bb → offspring could be BB or Bb (no contribution to "bb")
     • Bb x Bb → could produce BB, Bb, or bb

2. Mother's Father (unknown) x Mother (Bb):

   • Possible combinations:
     • BB x Bb → offspring could be BB or Bb (no contribution to "bb")
     • Bb x Bb → could produce BB, Bb, or bb

Conclusions on Missing Combinations:

Based on the available information, the missing allele combinations could refer to the genotypes of the Father’s Father and the Mother’s Father, which we can summarize as follows:

1. Father’s Father: (Possible combinations could be):

   • BB
   • Bb

2. Mother’s Father: (Possible combinations could be):

   • BB
   • Bb

Summary:

The complete allele combinations that are missing are the genotype of Father’s Father (can be BB or Bb) and the genotype of Mother’s Father (can also be BB or Bb).