Question

The common grackle is a species of robin-sized blackbirds that are fairly common (hence the name) over most of the United States. Suppose that long tails (L) were dominant to short tails (l) in these birds. A female short-tailed grackle mates with a male long-tailed grackle whose mother was short tailed and father had a long tail. What is the probability of a short-tailed offspring?

Answer 1

The probability of a short-tailed offspring in this scenario is 1/4 or 25%. This is because the female grackle has the genotype ll (homozygous recessive) and the male grackle has the genotype Ll (homozygous dominant). When these two genotypes are crossed, the resulting offspring can have any of the three genotypes (LL, Ll, or ll) with equal probability. Since one of these genotypes (ll) is associated with short tails, the probability of a short-tailed offspring is 1/4 or 25%.

Answer 2

Answer:
Long tail (Ll) = 1/2 or 50%
Short tail (ll) = 1/2 or 50%
Step-by-step explanation:
This question involves a single gene coding for tail length in grackle birds. The allele for long tails (L) were dominant to short tails (l) in these birds. This means that a bird that is heterozygous (Ll) for the gene will be phenotypically long tailed.
According to the question, a female short-tailed grackle (ll) mates with a male long-tailed grackle that had one parent with a long tail and one parent with a short tail. This male grackle will have a genotype: Ll because of his parental genotype. Hence, crossing ll × Ll, the following gametes will be produced by each parent:
Ll (male) = L and l
ll (female) = l and l
Using these gametes in a punnet square (see attached image), the following proportion of offsprings will be produced:
Ll, Ll, ll and ll
2 Ll out of 4 are long-tailed i.e 1/2 or 50% probability
2 ll out of 4 are short-tailed i.e 1/2 or 50% probability