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Testosterone is a steroid hormone that belongs to a group of male sex hormones called androgens - AQA - A-Level Biology - Question 2 - 2020 - Paper 1
Question 2
Testosterone is a steroid hormone that belongs to a group of male sex hormones called androgens. 1. Steroid hormones are hydrophobic. Explain why steroid hormones ... show full transcript
Worked Solution & Example Answer:Testosterone is a steroid hormone that belongs to a group of male sex hormones called androgens - AQA - A-Level Biology - Question 2 - 2020 - Paper 1
Step 1
Explain why steroid hormones can rapidly enter a cell by passing through its cell-surface membrane.
Answer
Steroid hormones, such as testosterone, are hydrophobic and lipid-soluble molecules. This enables them to diffuse through the phospholipid bilayer of the cell membrane without requiring any energy or specific transport mechanisms. Their hydrophobic nature allows them to easily navigate the lipid environment of the membrane, granting them rapid entry into the cell.
Step 2
Suggest and explain why testosterone binds to a specific AR.
Answer
Testosterone binds to a specific androgen receptor (AR) due to the complementary shapes of the hormone and the receptor. The AR has a specific tertiary structure that allows it to recognize and bind to testosterone specifically. This binding is facilitated by the compatible shapes and chemical properties, ensuring that the interaction is specific and effective.
Step 3
Suggest how the AR could stimulate gene expression.
Answer
Once testosterone binds to the AR, the receptor undergoes a conformational change, allowing it to bind to specific DNA sequences in the promoter regions of target genes. This interaction can recruit RNA polymerase and other transcription factors, resulting in the initiation of transcription, leading to gene expression. The AR acts as a transcription factor, modulating the expression of genes that influence male characteristics and behaviors.
Step 4
What can you conclude from the data in Table 1?
Answer
From the data in Table 1, we can conclude that the number of CAG repeats in the AR gene has a significant association with prostate cancer risk. Specifically, individuals with 16 or fewer CAG repeats show a significant probability (P = 0.02) of association with prostate cancer, indicating a higher risk. Conversely, individuals with 17 or more repeats do not show a significant association, as their P values are above 0.05, suggesting that chance may account for these findings.
Step 5
What can you conclude from the data in Table 1?
Answer
Further analysis indicates that with increasing CAG repeats, the significance in association with prostate cancer diminishes. For example, while those with ≤16 repeats display a strong significant association, the data shows less than 5% probability of being due to chance. In contrast, individuals with 17 or more CAG repeats have progressively higher P values, pointing to a lack of significant correlation, thus reinforcing the importance of the CAG repeat number in assessing prostate cancer risks.