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BRCA1 and BRCA2 are human genes that code for tumour suppressor proteins - AQA - A-Level Biology - Question 10 - 2022 - Paper 1
Question 10
BRCA1 and BRCA2 are human genes that code for tumour suppressor proteins. Mutations in BRCA1 and BRCA2 can cause cancer (lines 1–2). Explain how. Genetic testing, u... show full transcript
Worked Solution & Example Answer:BRCA1 and BRCA2 are human genes that code for tumour suppressor proteins - AQA - A-Level Biology - Question 10 - 2022 - Paper 1
Step 1
Explain how mutations in BRCA1 and BRCA2 can cause cancer
Answer
Mutations in the BRCA1 and BRCA2 genes lead to changes in the DNA base sequence or the triplet code. This can result in modified protein production, altering amino acid sequences, and impairing the normal functioning of tumor suppressor proteins. Consequently, cells may undergo rapid and uncontrollable division, increasing the risk of cancerous growth.
Step 2
Describe how this DNA could be screened for all known harmful mutations in both genes
Answer
Genetic testing for harmful mutations in the BRCA genes can be performed using a procedure such as PCR (Polymerase Chain Reaction) to amplify specific DNA sequences from saliva samples. The DNA can then be analyzed using techniques such as electrophoresis to separate the DNA fragments. Additionally, labeled DNA probes can be utilized to hybridize with the target sequences, allowing for the identification of mutations through various detection methods, such as fluorescence.
Step 3
Suggest and explain how these drugs are an effective treatment of ER-positive breast cancers
Answer
The drugs used for treating ER-positive breast cancers often bind to the estrogen receptor (ER) and can prevent the hormone estrogen from exerting its effects. By blocking the receptor, these drugs lower the stimulation of transcription factors that drive cancer cell growth. Hence, they effectively reduce tumor size and progression by interfering with the cancer cells' reliance on estrogen.
Step 4
Explain why the results of blood tests may not be conclusive when testing for prostate cancer
Answer
Blood tests for prostate cancer may yield elevated levels of PSA (Prostate-Specific Antigen) which can be high for reasons other than cancer, such as urinary infections or benign prostatic hyperplasia. This ambiguity can lead to false positives, making the results inconclusive for accurate prostate cancer diagnosis.
Step 5
Suggest and explain how treatment with drugs might be able to reverse the epigenetic changes that cause cancers
Answer
Drugs targeting epigenetic changes may function by modifying the methylation status of DNA. For instance, these treatments can increase the methylation of oncogenes, leading to repression of their expression, or decrease the methylation of tumor suppressor genes, resulting in the re-activation of their protective functions. This dynamic restoration of gene regulation can help reverse cancerous transformations in cells.