The BRCA1 gene is expressed in breast and ovarian cells; this expression is regu
ID: 215656 • Letter: T
Question
The BRCA1 gene is expressed in breast and ovarian cells; this expression is regulated by steroid hormones such as estrogen and progesterone. When the receptor of estrogen is bound with estrogen, it is activated and in turn, produces a substance that binds to a certain base sequence in the corresponding gene, and increases the rate of gene expression. This sequence is:
A. A signaling sequence in the transcription area
B. A sequence in the terminator of the gene
C. A sequences at the junction of exons and introns
D. ribosome recognition site of the mRNA
E. A sequence upstream to the starting point of the transcription region
The presence of a poly-A tail on a molecule of RNA found in the cytoplasm indicates that:
A. A 5’ cap will be attached later
B. The introns will be removed soon
C. The introns have already been removed
D. The mRNA is not mature yet
E. This is a tRNA molecule
Explanation / Answer
Ans.1. Estrogen hormone activates a transcription factor, after binding with estrogen receptor and increases the expression of BRCA1 gene. This transcription factor binds with the upstream controlling sequence, a sequence upstream to the start point of the transaction region and increases gene expression. Hence, the correct answer is option (E).
2. The presence of poly-A tail on RNA molecule, found in cytoplasm indicates that the introns have already removed. Introns are removed by the process of splicing, which occurs in nucleus during or after transcription. Since, this RNA molecule is found in cytoplasm, all introns have been removed before the transport of the molecule from nucleus to cytoplasm. Hence, the correct answer is option (C).
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