ONLY C AND D GENETICS: upcoming exam, please help explain the following. Thank y
ID: 136193 • Letter: O
Question
ONLY C AND D
GENETICS: upcoming exam, please help explain the following. Thank you. (Please explain the key in more detail, why is that the answer.)
1 The following sequence of double stranded DNA encodes a hypothetical protein called GEN in a bacteria. Transcription starts at and includes the C-G base pair in Bold. The underlined T-A base pair indicates the transcription terminator. 3'-AAGCGSATACCTCCCAGTAGATGCTCCGGGGCTAGTGATTTCCAAC-5' A) What are the first 9 bases of the transcribed RNA? Be sure to label the 5' and 3' ends of the RNA 5' CCCCUAUGG3' B) What are the first 4 amino acids of the subsequent polypeptide? Be sure to label the N- and C- termini. N-MET-GLU-GLY-HIS C C) How many amino acids long is the GEN polypeptide? 10 AMINO ACIDS D) You identify a strain of bacteria containing a mutant tRNA that is capable of adding a tryptophan residue when it recognizes the stop codon UAG in the mRNA. The GEN polypeptide would be (longer, shorter, the same) in the presence of the mutant (nonsense suppressor) Trp tRNA? SAME TI one sequence below.Explanation / Answer
For Answering C and D,
It is necessary to explain B also.
The Transcription starts at C-G pair according to the question. But the translation starts only at the "AUG(methionine)" site in mRNA which is after 7bases according to the given sequence. From there 3 codons code the aminoacids and form the peptide chain. After 10 amino acids, TAA (UAA in mRNA) comes which is a stop codon for translation (mRNA to protein). so the chain will be terminaed and will contain 10 amino acids where first 4 amino acids will be
ATG- Methionine
GAG- GLU
GGT-GLY
CAT-HIS
So, the peptide is 10 amino acids long. [This is the answer of C]
D) answer: According to the question, If the mRNA chain contain UAG then only it can add tryp.
The mRNA chain will contain UAG, but during translation the chain will be read by RNA polymerase from AUG only and then the UAG will not come in the frame, i.e triplet codon frame. so Tryp will not be added in the polypeptide chain during translation. Thus the polypetide length will be same.
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