Question

In Labrador retrievers, the allele for black fur (B) is dominant over brown fur (b). What are the correct genotypes for black labs and brown labs?

A) Black labs are BB or Bb; brown labs are bb
B) Black labs are BB; brown labs are Bb or bb
C) Black labs are Bb only; brown labs are bb
D) Black labs are bb; brown labs are BB or Bb

Answer 1

Black labs can be BB (homozygous dominant) or Bb (heterozygous), while brown labs are bb (homozygous recessive). The correct option is B) Black labs are BB; brown labs are Bb or bb

Step-by-step explanation:

In Labrador retrievers, the allele for black fur (B) is dominant over brown fur (b). This means that if a Labrador inherits a Black allele (B) from either parent, it will have black fur. Hence, the correct genotypes for black labs can be BB (homozygous dominant) or Bb (heterozygous).

On the other hand, brown labs will only have brown fur if they inherit two copies of the recessive brown allele (bb). Therefore, the correct genotype for brown labs is bb (homozygous recessive). The correct option is B) Black labs are BB; brown labs are Bb or bb