9. Below is a DNA sequence of part of a hypothetical wild-type bacterial genome.

Question

9. Below is a DNA sequence of part of a hypothetical wild-type bacterial genome. The nucleotides are numbered 1 to 100. Transcription begins with and includes the T/A (top strand/botom strand) base pair at position 7 (indicated by the arrow), and proceeds from left to right along the DNA. Translation of the transcript yields the peptide of interest 10 20 30 40 50 5" TA 5 51 60 70 80 90 100 (a) What are the first 12 nucleotides of the resulting messenger RNA (mRNA)? Indicate the 5' and 3 ends of the mRNA (2 marks) Second Letter uuu Phe ucu UAA Stop UGA Stop A CAU His cou CUA letter AUU AUG Met ACC Arg GoU GAU Asp GGU Glu GGA Page 12 of 14

Explanation / Answer

Ans. a) After transcription from DNA to mRNA sequence the thymine would be replaced by uracil. Hence the sequence from 5' to 3' end which is TCAGATTACGTA in case of DNA, it would be AGUCUAAUGCAU in case of mRNA.

Ans. b)(i) AUG codes for the initiation codon and UAA,UAG and UGA responsible for termination of chain. Hence considering it the total number of codons which code for amino acids there would be 10 amino acids in the peptide chain.

Ans. b)(ii) The first four amino acids are methionine, isoleucine, leucine and leucine.

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