11. Below is the double-stranded DNA sequence of a new regulator in the Lac oper
ID: 268837 • Letter: 1
Question
11. Below is the double-stranded DNA sequence of a new regulator in the Lac operon (made up!) Transcription starts at the Transcription Start Site (TSS) after the promoter (shown in yellow), and proceeds in the direction of the arrow. Transcription stops at the end of the Transcription Terminator (shown in blue). ed 5'-TATAAACGATCTGACAGCATTAACTGCATCGCATATGCATCATTGGCCCTCGCGCTAGCGCGTAGGATCGTGATTTTTTG-3' 3-ATATTTGCTAGACTGTCGTAATTGACGTAGCGTATACGTAGTAACCGGGAGCGCGATCGCGCATCCTAGCACTAAAAAAC-5' a) What is the sequence of the mRNA produced from this gene? Label the 5' and 3' ends, the UTRs, and coding sequence (CDS) on the mRNA sequence. b) What is the sequence of the protein produced from the mRNA in (b)? Label the N and C termini. c) Amutation was found that changes a G/C basepair to an A/T basepair at position 45 to change CATGG to CATTAG (at position marked by "d" above). What would be the consequence? d) If a mutation was found where a C/G basepair was deleted between position 55 (sequence changes from CGCGCTA to CGCGTA at position "e" marked above). What would be the consequence e) Amutation was found that inserts a T/A pair between position 35 & 36 (ATGCAT to ATTGCAT at position "f" above). What would be the consequence?Explanation / Answer
a)
5'-UAUAAACGAUCUGACAGCAUUAACUGCAUCGCAAUGCAUCAUUGGCCCUCGCGCUAGCGCGUAGGAUCGUGAUUUUUUG-3'
Underlined bases are coding sequence [starting from AUG as start codon till UAG (excluded) as stop codon].
Italic bases are UTRs.
b) Protein sequence coded from the mRNA will be
N-MHHWPSR-C
Only coding sequence will be translated to protein.
c) The mutation is introducing a stop codon by changing TGG to TAG, which results in early termination of translation. The protein coded by the mutated sequence will be MHH.
d) The new protein sequence translated from the mutated sequence will be MHHWPSRSA.
e) The mutation will change the start codon, thus the translation will not start. There is not other start codon site, so no protein will be translated from the mutated sequence.
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