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
Match each person with the correct allele combination.



(1 point)

Mother’s Father
Father
Father’s Father

Answer 1

To match each person with the correct allele combination for the given alleles related to brown (B) and blonde (b) hair, we can deduce the possible allele combinations based on the stated relationships:

1. Father’s Mother (Bb): Already given.
2. Mother’s Mother (BB): Already given.
3. Mother (Bb): Already given.
4. Child (bb): Already given.

Now, we need to deduce the allele combinations for:

• Father’s Father
• Father
• Mother’s Father

Analysis:

1. Child (bb): The child is blonde (bb), which means both alleles are recessive. Thus, each parent must have contributed a recessive allele (b).

2. Mother (Bb): The mother can pass on either a B (dominant) or b (recessive) allele. Since the child is bb and she has one b allele, the mother can provide a b allele.

3. Father: Since the child is bb and the mother is Bb, the father must be contributing the recessive b allele. For the father to have a blonde-haired child, he must have at least one b allele. Therefore, the father must also be Bb (brown hair).

4. Father’s Father: To confirm the father’s father's genotype, since the father (Bb) is brown-haired, he has to inherit one of his B alleles from his father. If the father is Bb (as deduced), this suggests the father’s father could be BB or Bb. However, we already established that both of the father's parents contribute the brown-haired phenotype, so the father’s father needs to also be BB (to account for needing one B each for both children). He cannot be Bb because having a blend would risk producing a blonde child (bb).

5. Mother’s Father: Since the mother’s mother is BB, ensuring the mother also inherits a B from her side. Therefore, needing a blonde (bb) combination for the mother’s father likely doesn't matter since it reinforces the BB designation. Hence, the mother’s father must be either BB or Bb. However, since the mother can pass along a b allele, the most likely combination for the mother's father, following the brown-haired parentage, would also be BB.

Summary of Matches:

• Father’s Father: BB (brown hair)
• Father: Bb (brown hair)
• Mother’s Father: BB (blonde is not possible)

Final Answer - Allele Combinations:

• Father’s Father: BB
• Father: Bb
• Mother’s Father: BB