Biology 9700 · AS & A Level · Principles of genetic technology

Principles of genetic technology — practice question

Sickle cell anaemia is a chronic, non-infectious disease. If it is not treated, sickle cell anaemia can cause severe pain and may be life-threatening. Sickle cell anaemia results from a base substitution mutation in the gene that codes for the β-globin polypeptide of haemoglobin. This changes the primary structure of the polypeptide, because valine is found instead of glutamine. As a result, red blood cells become abnormally sickle-shaped and stick to one another inside blood vessels. Symptoms of sickle cell anaemia include painful episodes when red blood cells obstruct capillaries in tissues and organs.
(a)[2]

Predict the effects on cells when sickle-shaped red blood cells obstruct capillaries in tissues and organs.

(b(i))[2]

Outline two benefits of genetic screening for sickle cell anaemia and SCT.

(b(ii))[3]

Explain: • why primers are needed in PCR • how the use of two specific primers permits the amplification of the normal, sickle cell anaemia and SCT genotypes. One mutation that produces HbS is a base substitution in the sixth codon of the β-globin gene. The normal codon GAG is changed to GTG. The normal-specific primer detects GAG whereas the mutant-specific primer detects GTG.

(b(iii))[2]

Deduce the genotypes and phenotypes of individuals A and B in Fig. 4.1.

(c(i))[4]

Explain how natural selection acts to preserve the sickle cell allele in populations in areas where malaria occurs.

(c(ii))[2]

Discuss two ethical reasons why parents using IVF may decide against PGD.

(c)[2]

Deduce the genotypes and phenotypes of individuals A and B in Fig. 4.1. A ........................................................ B ........................................................

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