A pedigree chart is provided, showing inheritance of a trait for hearing/deafness. The chart depicts three generations. The question asks to: a) determine the number of males, b) determine the number

Squares represent males.

• Jon (Generation 1)
• Paul (Generation 2)
• Lyall (Generation 3) There are 3 males.
• 3

b)

Each level represents a generation.

• Generation 1: Jon and Linda
• Generation 2: Gabby, Paul, and Fiona
• Generation 3: Mieke and Lyall There are 3 generations.
• 3

6.2

a)

Since Jon has at least one dominant H allele, he can hear.
The phenotype of Jon is:

• Hearing

b)

Therefore, Paul's genotype is:

• $\boxed{\text{Hh}}$

6.3
Lyall is deaf, meaning his genotype is $\text{hh}$. For Lyall to have this genotype, he must have inherited one 'h' allele from each of his parents. His parents are Paul and Gabby. Paul's genotype is $\text{Hh}$ (as determined in 6.2b), so he carries the recessive allele and can pass it on. Gabby is shown as hearing (unshaded circle), but since she had a deaf child ($\text{hh}$), she must also carry the recessive 'h' allele. Therefore, Gabby's genotype is also $\text{Hh}$. Both parents are heterozygous carriers for deafness, and they each passed on their recessive 'h' allele to Lyall, resulting in his deafness.

6.4

• Lyall is deaf, so his genotype is $\text{hh}$.
• The woman is homozygous dominant for hearing, so her genotype is $\text{HH}$.

Parents: $\text{hh}$ (Lyall) $\times$ $\text{HH}$ (Woman)

Gametes from Lyall: h, h
Gametes from Woman: H, H

All possible offspring genotypes are $\text{Hh}$.
All offspring will have the phenotype of hearing.

Since all offspring are $\text{Hh}$ (hearing), there is no chance of having a deaf child.

• 0%