31. Consider the dihybrid cross, YySs x YySs, where Y refers to yellow fur, y refers to white fur, S refers to short fur, and s refers to long fur. Capitalized letters refer to dominant traits, and lowercase letters refer to recessive traits. How many offspring have white, long fur?
Answer: A
One offspring has white, long fur.
In the dihybrid cross YySs x YySs, the combination of traits leads to the identification of the offspring's fur color and length. The only combination that results in white, long fur is yyss, which occurs in 1 out of the 16 possible genetic combinations.
A) 1
This option is correct because the combination of alleles required for white fur (yy) and long fur (ss) occurs only once in the 16 possible genotype combinations from the dihybrid cross. Specifically, the combination yyss represents one unique outcome.
B) 4
This option is incorrect, as having 4 offspring with white, long fur would imply that there are multiple combinations leading to the genotype yyss, which is not the case. The correct calculation yields only 1 occurrence of the required genotype.
C) 8
This option is also incorrect because it suggests that there would be 8 offspring with the combination of white, long fur. The genetic analysis shows that this combination occurs only once in the total of 16 combinations, making this option inaccurate.
D) 12
This option is incorrect as well, indicating a misunderstanding of the inheritance pattern. The combination of traits resulting in white, long fur (yyss) does not occur frequently enough to produce 12 offspring in the outcome of the dihybrid cross.
Conclusion
The correct answer, 1, reflects the accurate genetic outcome of the dihybrid cross YySs x YySs, as only one of the 16 possible combinations results in white, long fur. All other options fail to represent the true genetic probabilities derived from this cross, demonstrating a clear understanding of Mendelian genetics.