B1 H - Sample set 1 Q6 Answers
6) (a) DNA is composed of four different DNA nucleotides.
(i) Which diagram represents the arrangement of the sugar, phosphate and the base in a DNA nucleotide? (1)
(i) Which diagram represents the arrangement of the sugar, phosphate and the base in a DNA nucleotide? (1)
(ii) An allele starts with the DNA sequence ATGCATGTACCG.
Give the sequence of the complementary DNA sequence. (1)
(iii) The length of one DNA nucleotide was measured at 3.3 × 10–10 metres. Calculate the approximate length of a gene containing 250 nucleotides in nanometres. (2)
Give the sequence of the complementary DNA sequence. (1)
(iii) The length of one DNA nucleotide was measured at 3.3 × 10–10 metres. Calculate the approximate length of a gene containing 250 nucleotides in nanometres. (2)
............................................................. nm
(b) The DNA of an organism determines its phenotype.
White tigers are produced because of a mutation of a single allele which usually produces the normal orange and yellow fur pigmentation.
The mutated allele is recessive.
Samba, a male white tiger, was bred with Rani. They had three offspring; two offspring have white fur and one has a normal fur pigmentation.
(i) State the genotype of Rani. (1)
(ii) The offspring with normal fur pigmentation was bred with a tiger that was heterozygous.
Use A/a to represent the alleles for fur pigmentation.
Predict, using the Punnett square, the percentage probability of the offspring from this cross having normal fur pigmentation. (2)
White tigers are produced because of a mutation of a single allele which usually produces the normal orange and yellow fur pigmentation.
The mutated allele is recessive.
Samba, a male white tiger, was bred with Rani. They had three offspring; two offspring have white fur and one has a normal fur pigmentation.
(i) State the genotype of Rani. (1)
(ii) The offspring with normal fur pigmentation was bred with a tiger that was heterozygous.
Use A/a to represent the alleles for fur pigmentation.
Predict, using the Punnett square, the percentage probability of the offspring from this cross having normal fur pigmentation. (2)
percentage probability = ............................................................. %
(c) Explain how two parents with a dominant phenotype can produce offspring expressing a recessive characteristic. (2)
(Total for Question 6 = 9 marks)
(Total for Question 6 = 9 marks)