ease indi possible codons A18. Amino acid number 4 is valine. Therefore, there a
ID: 207660 • Letter: E
Question
ease indi possible codons A18. Amino acid number 4 is valine. Therefore, there are present in the mRNA and amino acid acyl tRNA synthetase(s) for this possible amino the T d. four; four a. Two; one b. four; one c. four; two A19. The "charging" reaction refers to a. binding of the codon to the anticodon b. binding of methionyl-tRNA to the P site c. formation of peptide bonds d. connecting the amino acid to the tRNA e, binding the ribosome to the mRNA A20. Which of the following is NOT made by copying a template? a Ribosomal RNA b. mRNA c. DNA d. polyA tail e. tRNA A21. A particular mature eukaryotic mRNA was formed by splicing to put the three exons together How many introns were removed? a. One b. two c. three d. four e. none start site for CAP. polymerase- RNA synthesis binding binding site site (promoter) operator Lacz gene above diagrams the lac operon of E. coli. It is expressed at high levels only in the presence of lactose and the absence of glucose. Questions A22 through A25 refer to this picture. A22. The operon is repressed by the lacl protein, which binds to the CAP binding site synthesis a. b. RNA polymerase binding site c. operator d. start site for RNA e. lacZ geneExplanation / Answer
A18. The answer is d. Four, four.
Explanation
As per given information, the valine is fourth amino acid so, there are four possible codons present in mRNA.
An amino acyl tRNA synthatase is an tRNA ligase which attaches the aprropriate amino acid onto its tRNA.
In humans, 20 different types of amino acids - tRNA are made by the 20 different aminoacyl-tRNA synthatase because one synthatase is specified for each amino acid of the genetic code.
A19. The charging reaction refers to:
The answer is d. connecting the amino acid to tRNA.
Explanation:
The binding of amino acid to tRNA by means of amino acyl-tRNA synthatase is called as charging. It is also called as loading reaction. As the tRNA is charged, ribosome transfers the amino acid from the tRNA to the growing peptide as per the genetic code.
A20. The answer is d. Poly A tail.
Explanation
PolyA tail is a long chain of adenine nucleotides that is added to a messenger RNA molecule during RNA processing to increase the stability of the molecule.
The main function of polyA tail is to protect the mRNA molecule from enzymatic degradation in the cytoplasm and also helps in transcription termination, export of the mRNA from the nucleus and translation.
A21. The answer is b. two
Explanation
If we have three exons together after splicing, two introns are removed. The first exon is present at 5' position and last i.e. 3rd exon is present at 3' position. In between these three exons, the introns are present alternately.
Thus, the position is: 5' ---- Exon 1 ---- Intron A ---- Exon 2 ---- Intron B ----- Exon 3 ---- 3'
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