Need help with parts a-f on this question Question 3 Shown below is a double-str

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Need help with parts a-f on this question Question 3 Shown below is a double-stranded bacterial (E. col) DNA sequence coding for a hypothetical protein. Both strands are shown; the top strand reads 5' to 3 left to right, while the bottom strand reads 5 to 3 right to left. The nucleotides are numbered 1 to 100. NOTE: For this problem, transcription begins with and includes the red and underlined C/G (top strand/bottom strand) base pair and RNA polymerase proceeds from left to right along the DNA 20 40 5 -GTGTCCGTCTAATATTGTGAGATGTTATATCCCGCCGTCAACACCATCAA-3 3'-CACAGGCAGATTATAACACTCTACAATATAGGGCGGCAGTTGTGGTAGTT-5 5 -ACAGGATAATCGCCTGCTGGGGCAAAGGCGGTGAAGGTAAAGGTGTTGCC-3 3 '-TGTCCTATTAGCGGACGACCCCGTTTCCGCCACTTCCATTTCCACAACGG-5 60 80 100 a) Which strand is used as a template for transcription, the top or the bottom? b) Where would the promoter be relative to the start of transcription? c) What are the first 15 nucleotides of the resulting mRNA? Indicate the 5" and 3 ends of the mRNA d) What are the first 5 amino acids translated from the resulting mRNA? Indicate the amino (NH,) and carboxy (COO) termini of the protein. e) Do the underlined nucleotides TAA (indicated in blue) encode a stop codon for the protein? Briefly explain your answer Consider the situations in parts (f-h) independently f) A mutation occurs which results in the insertion of an extra G/C (top strand/bottom strand) base-pair immediately after base pair 11 (shown in bold). What effect will this insertion mutation have on the mRNA transcript and resulting protein? g) A different mutation results in the substitution of the T/A base pair at position 30 (shown in bold and underlined) with a G/C base pair. How would this mutation affect the sequence of the protein that is produced? h) A third mutation occurs which results in the substitution of the C/G base pair at position 42 (shown in bold italics) to a T/A base pair. How would this mutation affect the sequence of the protein that is produced?

Explanation / Answer

a) The strand which runs from 3' to 5' direction is known as template strand and the strand which runs from 5' to 3' direction is known as coding strand.

b) In prokaryotic DNA, there are two promotor consensus. The TTGACA sequence will be 35 base pairs upstream of transcription start site and the TATAAT sequence will be 10 basepairs upstream of transcription start site.

c) The first 15 nucleotides of the resulting mRNA is 5'- CUAAUAUUGUGAUGU - 3'

d) NH3 Leu-Ile-Leu-stop-Cys COO-

e) The underline nucleotides TAA corresponds to the codon UAA in mRNA which is one of the stop codons. The other two stop codons are UAG and UGA.

f) The insertion of G/C base pair immediately after the base pair 11 would result in insertional mutation. It changes the sequence of codons in mRNA and therefore the amino acids in the resulting protein.

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