1. Polydactyly is caused by a dominant allele, D. The recessive allele of the gene is represented by d. Use one genetic diagram to show the inheritance of the polydactyly gene by R and S.

P generation Father (P) Mother(Q)

Phenotype Polydactyly Normal

Genotype Dd dd

Gamete D d d d

Fertilization

Punnett Square for F1 generation

F/M

d

d

D

Dd

Dd

d

dd

dd

Phenotypic ratio: 1:1

Affected: Unaffected

Offspring: Offspring

Genotypic ratio: 1:1

Dd: dd