$$$5 B R C A 2$$$ is a tumour-suppressor gene. Its gene product, BRCA2, is involved in DNA repair. If the Scientists have identified hundreds of mutations in BRCA2, but not all of these mutations will increase the risk of cancer. One specific mutation in BRCA2, known as 999del5, is found in $$$0.6 \%$$$ of the general global population. Iceland is an island country in the North Atlantic Ocean. The ancestors of most of the current population are people who arrived to settle in Iceland in AD 874. In the Icelandic population, mutation 999del5 is the cause of $$$7-8 \%$$$ of breast cancer cases in women and $$$40 \%$$$ of breast cancer cases in men. This is much higher than the percentage of breast cancer cases in the general global population. (i) Suggest and explain how mutation 999del5 accounts for a very high percentage of breast cancer cases in Iceland compared with the general global population. ....................................................................................................................................... . ....................................................................................................................................... . ....................................................................................................................................... . ....................................................................................................................................... . ....................................................................................................................................... . ....................................................................................................................................... . ....................................................................................................................................... . ................................................................................................................................. (ii) One of the largest global genetic screening programmes for breast cancer involves identifying people with mutations in BRCA2. Outline the advantages of genetic screening for mutations in BRCA2. ....................................................................................................................................... . ....................................................................................................................................... . ....................................................................................................................................... . ....................................................................................................................................... . ....................................................................................................................................... . ................................................................................................................................. (iii) Suggest one advantage to a country of a genetic screening programme for breast cancer that screens for specific mutations in BRCA2 in the population. ....................................................................................................................................... . .................................................................................................................................

Biology

IGCSE&ALevel

CAIE

Exam No：9700_s24_qp_43 Year：2024 Question No：5(b)

Answer:

Knowledge points:

6.2.1 state that a polypeptide is coded for by a gene and that a gene is a sequence of nucleotides that forms part of a DNA molecule

6.2.2 describe the principle of the universal genetic code in which different triplets of DNA bases either code for specific amino acids or correspond to start and stop codons

6.2.3.1 RNA polymerase

6.2.3.2 messenger RNA (mRNA)

6.2.3.3 codons

6.2.3.4 transfer RNA (tRNA)

6.2.3.5 anticodons

6.2.3.6 ribosomes

6.2.4 state that the strand of a DNA molecule that is used in transcription is called the transcribed or template strand and that the other strand is called the non-transcribed strand

6.2.5 explain that, in eukaryotes, the RNA molecule formed following transcription (primary transcript) is modified by the removal of non-coding sequences (introns) and the joining together of coding sequences (exons) to form mRNA

6.2.6 state that a gene mutation is a change in the sequence of base pairs in a DNA molecule that may result in an altered polypeptide

6.2.7 explain that a gene mutation is a result of substitution or deletion or insertion of nucleotides in DNA and outline how each of these types of mutation may affect the polypeptide produced

Answer:

Knowledge points:

Solution:

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