In genetics, a genotype is said to be homozygous dominant when it has two identical alleles that are both dominant. Dominance refers to the relationship between alleles, where the dominant allele will mask the effect of the recessive allele.
Let’s analyze the options provided:
- a) tt – This genotype is homozygous recessive because both alleles are recessive.
- b) ff – Similarly, this genotype is also homozygous recessive.
- c) xy – This represents a heterozygous condition (assuming ‘x’ and ‘y’ are alleles), and thus cannot be homozygous dominant.
- d) ss – This genotype is homozygous, and if ‘s’ is dominant, then it is homozygous dominant.
Based on this analysis, the answer is d) ss if ‘s’ represents a dominant allele. Therefore, ‘ss’ is the only option that represents a homozygous dominant genotype.