The roles of genes in — Paper 1 · A Level Biology 9700

22 In the DNA sequence for sickle cell anaemia, adenine replaces thymine in a CTT triplet, forming the triplet CAT. During synthesis of the sickle cell haemoglobin molecule, the amino acid valine is incorporated instead of glutamic acid. What is the anticodon in the transfer RNA molecule carrying this valine? A CAT B CAU C GTA D GUA

1 marks

Answer: B

This question in 9700/11 Oct/Nov 2004

23 What is the minimum number of base substitutions required to change the nucleotide sequence of the HbA (normal) allele to the HbS (sickle cell) allele? A 1 B 2 C 3 D 4

1 marks

Answer: A

This question in 9700/12 May/June 2010

39 What is the minimum number of base substitutions required to change the nucleotide sequence of the HbA (normal) allele to the HbS (sickle cell) allele? A 1 B 2 C 3 D 4

1 marks

Answer: A

This question in 9700/13 May/June 2010

22 S and T are products of a biochemical pathway. A different enzyme, coded for by different specific genes, catalyses each step in the pathway. gene 1 gene 2 gene 3 S enzyme 3 enzyme 1 enzyme 2 P Q R enzyme 4 T gene 4 What is the possible outcome to the pathway if a mutation in gene 3 leads to an inactive enzyme? A There is a decrease in the activity of gene 1 and gene 2. B There is an accumulation of product S. C There is an increase in the rate of reaction of enzyme 4. D There is an increase in the production of T.

1 marks

Answer: D

This question in 9700/12 Oct/Nov 2010

19 A gene codes for the production of a protein, p53, that binds to damaged DNA during interphase and prevents its replication. A carcinogen in cigarette smoke mutates this gene. Which statement explains why this mutation may cause cancer? A Lack of p53 allows cells to undergo mitosis. B Lack of p53 allows cells with damaged DNA to replicate. C The carcinogen in cigarette smoke increases the rate of cell division. D The p53 causes uncontrolled cell division.

1 marks

Answer: B

This question in 9700/11 Oct/Nov 2011

21 Gene mutations in either the BRCA71 or the BRCA2 genes are responsible for the majority of hereditary breast cancer in humans. The proteins produced by the two genes migrate to the nucleus where they interact with other proteins, such as those produced by the tumour suppressor gene, p53 and the DNA repair gene, RADS1. Which combination of gene activity is most likely to result in breast cancer? gene OAS. 53 RAD51 A Vv Vv J B Vv V x c V x J D x x x key / = gene produces normal protein X =gene produces abnormal protein or no protein

1 marks

Answer: D

This question in 9700/13 May/June 2013

20 Which term best describes the length of DNA that codes for the synthesis of a polypeptide? A anticodon B codon C gene D nucleotide

1 marks

Answer: C

This question in 9700/13 Oct/Nov 2013

21 The statements are about genes and proteins involved in breast cancer. e The protein coded by the BRAC7 gene inhibits the growth of breast cancer cells. e The protein coded by the RAD57 gene is required for the repair of damaged DNA. Which combination of genes is most likely to result in breast cancer? gene BRAC1 RAD51 v v key ¥ =normal active gene X = mutated gene 0 OW D> ~ «K & x v x

1 marks

Answer: D

This question in 9700/13 May/June 2014

18 The statements are about genes and proteins, involved in breast cancer. e The protein coded by the BRAC7 gene inhibits the growth of breast cancer cells. e The protein coded by the p53 gene suppresses tumours. Which combination of genes is most likely to result in breast cancer? gene BRAC1 p53 A x x B x J Cc J x D J J key ¥ =normal active gene X = mutated gene

1 marks

Answer: A

This question in 9700/13 Oct/Nov 2014

11 Haemoglobin, a globular protein, consists of four polypeptide chains, two alpha chains and two beta chains. In normal individuals, in the DNA which codes for each beta chain, the sixth triplet has a code for glutamic acid. In individuals with sickle cell anaemia this base triplet mutates and codes for valine. What does this mutation change in the haemoglobin molecule? A the iron content B the primary structure C the quaternary structure D the secondary structure

1 marks

Answer: B

This question in 9700/13 Oct/Nov 2015

18 Gene mutations in either the BRCA7 or the BRCA2 genes are responsible for the majority of hereditary breast cancer in humans. The proteins produced by the two genes migrate to the nucleus where they interact with other proteins, such as those produced by the tumour suppressor gene, p53, and the DNA repair gene, RADS1. Which combination of gene activity is most likely to result in breast cancer? gene Ona > p53 RAD51 A J J V B J J x Cc J x V D x x x key / = gene produces normal protein X =gene produces abnormal protein or no protein

1 marks

Answer: D

This question in 9700/13 Oct/Nov 2016

24 A gene codes for the sequence of amino acids in a single polypeptide. Haemoglobin consists of two α-globins and two β-globins. How many genes are needed to code for a single haemoglobin molecule? A 1 B 2 C 4 D 8

1 marks

Answer: B

This question in 9700/13 Oct/Nov 2017

25 A single substitution in an allele of the gene coding for haemoglobin results in sickle cell haemoglobin. The mRNA sequence for three amino acids for normal haemoglobin is shown. CCUGAAGAG The mRNA sequence for sickle cell haemoglobin is shown. CCUGUAGAG The table shows some of the triplet codes for two amino acids. DNA triplet codes amino acid CTC Glu CTT Glu CAT Val CAC Val Which row is correct for the substituted DNA nucleotide of the allele and the substituted amino acid of the protein? DNA new amino nucleotide acid A A Glu B A Val C T Glu D T Val

1 marks

Answer: B

This question in 9700/13 Oct/Nov 2017

24 A gene codes for the production of a protein, p53, that binds to damaged DNA during interphase and prevents its replication. A carcinogen in cigarette smoke mutates this gene. Which statement explains why this mutation may cause cancer? A Cells with no p53 are allowed to undergo mitosis. B Cells with no p53 allow their damaged DNA to replicate. C The carcinogen in cigarette smoke increases the rate of cell division. D The p53 causes uncontrolled cell division.

1 marks

Answer: B

This question in 9700/13 May/June 2019