Below is a drawing of a gene beginning with the sequence starting just past the

Question

Below is a drawing of a gene beginning with the sequence starting just past the promoter. This gene codes for two important proteins: the first, calcitonin, is a hormone produced by thyroid cells when blood calcium levels are high. Calcitonin causes bone to take up calcium, and reduces calcium uptake by intestines and kidney. Thyroid cells secrete Calcitonin. The second protein is CGRP (calcitonin gene-related peptide), a neurotransmitter produced by cells of the nervous system, especially sensory neurons
There are five exons whose functions: Exon1: not translated but essential for ribosome binding and for beginning translation initiation Exon2: encodes a signal sequence, later removed from the protein that helps ensure that this protein is ultimately processed in the Golgi complex and secreted out of the cell. Exon3: calcitonin coding exon Exons4+5:Together in code CGRP, the neurotransmitter
A) Explain how, In two sentences or less, calcitonin can be made in thyroid cells, but CGRP is made in neurons. (Must be 2 sentences or less!)
B) Continue in the calcitonin/CGRP example, for Exon 1, is the RNA from this DNA included in the final transcript for CGRP and calcitonin? If so, what is this region called?
C) If exon 2 was not included in the final transcript, in what cellular location would the final protein products end up?
D) When exon 2 is included, what binds to the amino acids produced and in what cellular location is translation completed?(so in one or two sentences state what this signal sequence does and very briefly how that works)
E) in thyroid and sensory neuron cells, is the DNA sequence encoding this gene the same? Yes or no

Explanation / Answer

A. There may be a specific transcription factor which recognizes different transcription start sites in each tissue. (Or) There could be proteins that are specifically expressed in each tissue that cause alternative splicing.

B. Exon 2 is called the 5-Untranslated region (5'-UTR)

C. Exon 2 is required for translocation to Golgi. If it is removed, the protein would end up in the cytosol.

D. Proteins destined to Golgi contain a signal sequence. This signal sequence is bound by proteins of the secretory pathway and target the protein to ER and then to Golgi.

E. Yes. The genomic sequence is same in both the tissues.

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