- The trait in question 20 is recessive. Affected individuals (filled symbols) must have the genotype 'aa'. Unaffected individuals can be either 'Aa' or 'AA', but since they have affected offspring, they must carry the recessive allele, making their genotype 'Aa'.
- The trait in question 21 is dominant. Affected individuals (filled symbols) have at least one dominant allele, so their genotype is 'Aa' (since an 'AA' individual would pass the trait to all offspring, which is not always the case here). Unaffected individuals (open symbols) must be 'aa'.
- For question 22: At least one parent has the trait.
- For question 23: If one of the parents is homozygous then all the children will have it. If both parents are heterozygous, then there is a 75% chance that they will have the trait.
- For question 24: All their children will have the trait.
- For question 25: If one of the parents is homozygous dominant then none of the children will have it. If both parents are heterozygous, then there is a 25% chance that they will have the trait.
- For question 26: Yes, example - heterozygous parents can make a homozygous recessive child.
Parent Tip: Review the logic above to help your child master the concept of pedigree worksheet.
