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02:23

Question
A species of mice can have long or short tails. If you crossed a male mouse which is heterozygous and has a long tail with a female mouse with a short tail, what would the expected phenotypic outcome be and why?
Responses
A 100% long tails due to the Law of Dominance.100% long tails due to the Law of Dominance.
B There is no way to predict the phenotypic ratio since one of the parents is heterozygous.There is no way to predict the phenotypic ratio since one of the parents is heterozygous.
C 75% long tails and 25% short tails because the dominant allele for long tail still masks the recessive short tail allele.75% long tails and 25% short tails because the dominant allele for long tail still masks the recessive short tail allele.
D 50% long tails and 50% short tails because the heterozygous genotype increases the percentage of offspring that might show the recessive phenotype, short tail.

Answer 1

To determine the expected phenotypic outcome when crossing a heterozygous male mouse (with a genotype of Ll, where L = long tail and l = short tail) with a female mouse that has a short tail (with a genotype of ll), we can set up a Punnett square.

The male mouse can contribute either L (long tail) or l (short tail), while the female mouse can only contribute l (short tail). This results in the following combinations:

1. Ll (long tail)
2. Ll (long tail)
3. ll (short tail)
4. ll (short tail)

From this analysis, we can observe the following outcomes:

• 50% (2 out of 4) are Ll (long tail)
• 50% (2 out of 4) are ll (short tail)

Thus, the expected phenotypic ratio from this cross is 50% long tails and 50% short tails.

The correct answer is:

D. 50% long tails and 50% short tails because the heterozygous genotype increases the percentage of offspring that might show the recessive phenotype, short tail.