Given the information provided, Sam has a genotype of DD for dark hair, which means he carries two dominant alleles for that trait. Martha, who has blonde hair, would have a genotype of either bb (homozygous recessive) or Bb (heterozygous), but since blonde hair is a recessive trait, she must be bb.
When Sam (DD) has a child with Martha (bb), all possible offspring will inherit one dominant D allele from Sam and one recessive b allele from Martha.
The possible genotype combinations for their child would be:
- D (from Sam)
- b (from Martha)
This results in the following genotype for the child:
- Db
Since D (dominant for dark hair) is the only allele present from Sam, the phenotype of the child will be dark hair.
In summary, the possible outcomes for Sam and Martha's child are:
- The child will have dark hair, with the genotype Db.
There are no possible outcomes for a child with blonde hair from this pairing, as the dominant dark hair trait will always be expressed in the offspring due to the presence of the dominant D allele from Sam.