36. In a population, there are two different alleles for a gene. D is dominant and d is recessive. If two organisms that are Dd mate, which of the following lists the results possible offspring?
Answer: B
The possible offspring from two Dd organisms are DD, Dd, and dd.
When two organisms that are heterozygous (Dd) mate, the possible combinations of their alleles can result in offspring with genotypes DD, Dd, and dd.
A) DD and dd
This option is incorrect because it does not account for the heterozygous offspring (Dd) that can also result from the mating of two Dd individuals. The Punnett square shows that both homozygous and heterozygous combinations are possible.
B) DD, Dd, and dd
This option is correct as it includes all the possible genotypes resulting from the cross between two Dd organisms. The combinations are: 25% DD, 50% Dd, and 25% dd, which accurately reflects the expected outcomes.
C) Dd and dd
This option is incorrect because it omits the homozygous dominant offspring (DD) that can occur from the mating of two Dd individuals. It only lists one of the heterozygous outcomes and the homozygous recessive outcome.
D) All Dd
This option is incorrect because it implies that all offspring will be heterozygous (Dd), which is not the case. The mating of two Dd organisms can produce offspring with different genotypes, including DD and dd.
Conclusion
The correct answer, B, encompasses all potential outcomes from the mating of two Dd organisms, including homozygous and heterozygous combinations. The other options fail to represent the complete range of genotypes that can arise from this genetic cross. Thus, B is the only option that accurately reflects the genetic possibilities.