B1 H - Sample set 1 Q4
4) Gregor Mendel investigated the genetics of peas.
He did not know about genes but showed that inherited characteristics can be dominant or recessive.
(a) Explain how Mendel used homozygous tall and homozygous short pea plants to show that the tall allele is dominant to the short allele. (2)
(b) Figure 4 shows a strawberry plant that has produced several runners and new strawberry plantlets are growing at the end of each runner. This is asexual reproduction.
He did not know about genes but showed that inherited characteristics can be dominant or recessive.
(a) Explain how Mendel used homozygous tall and homozygous short pea plants to show that the tall allele is dominant to the short allele. (2)
(b) Figure 4 shows a strawberry plant that has produced several runners and new strawberry plantlets are growing at the end of each runner. This is asexual reproduction.
(i) Explain why asexual reproduction in strawberries is beneficial to strawberry farmers. (2)
(ii) Strawberry fruits, containing seeds, are produced after a flower is fertilised. Explain why seed production is an advantage to the strawberry plant. (2)
(c) Duchenne muscular dystrophy is a sex-linked recessive genetic disorder caused by a mutation on a single gene on the X-chromosome.
The letter D can be used for the dominant allele and the letter d for the recessive allele.
Figure 5 shows the inheritance of Duchenne muscular dystrophy in a family.
(ii) Strawberry fruits, containing seeds, are produced after a flower is fertilised. Explain why seed production is an advantage to the strawberry plant. (2)
(c) Duchenne muscular dystrophy is a sex-linked recessive genetic disorder caused by a mutation on a single gene on the X-chromosome.
The letter D can be used for the dominant allele and the letter d for the recessive allele.
Figure 5 shows the inheritance of Duchenne muscular dystrophy in a family.
(i) What is the percentage chance of any child from person A inheriting the mutated allele? (1)
(ii) Explain the conclusion that can be made about the genotype of person C. (2)
(Total for Question 4 = 9 marks)
(Total for Question 4 = 9 marks)