6.1 Reproduction

EasyMedium
1234567891011121314151617181920212223242526272829303132333435363738394041424344454647
Question 32
Medium

Polydactyly is an inherited condition where a person is born with extra fingers or toes. It is caused by a dominant allele PPP. The recessive allele ppp results in a normal number of digits.

The pedigree chart below shows the inheritance of polydactyly in a family:

Pedigree chart showing 3 generations of a family labeled with numbers 1 to 15. A key indicates squares represent males and circles represent females. Shaded shapes show individuals with polydactyly (caused by a dominant allele P), and unshaded shapes show individuals with normal digits (recessive genotype pp). Generation I: Male 1 (shaded) and Female 2 (unshaded) have children: Female 3 (shaded), Male 4 (shaded), Female 5 (unshaded), and Female 6 (unshaded). Generation II: Male 4 (shaded) partners with unaffected Female 7 (unshaded) to have children: Male 8 (shaded), Female 9 (unshaded), Female 10 (unshaded), and Female 11 (shaded). Generation III: Male 8 (shaded) partners with unaffected Female 12 (unshaded) to have children: Female 13 (shaded), Male 14 (shaded), and Female 15 (unshaded).

a.

Give the genotype of Person 1 and explain your answer.

[3]
b.

Person 8 and Person 12 are expecting a fourth child. What is the probability of this child having polydactyly? Describe the Punnett square to support your answer.

[5]
c.

Explain how the pedigree chart shows that the allele for polydactyly is not on the Y chromosome.

[2]

6.1 Reproduction Questions

  1. GCSE
  2. /Biology
  3. /6.1 Reproduction