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Which one of the following pairs is correctly matched with regard to the codon and the amino acid coded by it?
Lysine is encoded by the codons AAA and AAG.
During portein synthesis in an organism at one point the process comes to a halt. Select the group of the three codons from the following, from which any one of the three colud bring about this halt.
Non sense codon or terminator codon are the codons that do not code for any amino acid. It is a set of three nucleotides for which there is no corresponding tRNA molecule to insert an amino acid into the polypeptide chain. Protein synthesis is hence terminated and the completed polypeptide released from the ribosome. Three stop codons are UAA (ochre), UAG (amber) and UGA (opal).
Mutations which generate any of these three codons in a position which normally contains a codons in a position which normally contains a codon specifying an amino acid are known as nonsense mutations.
The binding site of tRNA with mRNA & amino acids respectively are
The anticodon loop of tRNA binds to the codon on mRNA during translation. The CCA end of tRNA binds to the amino acid, which is then added to the growing polypeptide chain. This is the correct binding pattern of tRNA with mRNA and amino acids during protein synthesis.
Match the triplet codons listed in column I with their amino acids mentioned in column II and select the correct option from the given codes.
|
Column I |
Column II |
|
A. GGG |
(i) Proline |
|
B. UUU |
(ii) Glycine |
|
C. CCC |
(iii) Arginine |
|
D. AAA |
(iv) Phenylalanine |
|
|
(v) Lysine |
The premature termination of polypeptide synthesis due to stop codon can be overcome via compensatory mutation in tRNA. This genetic phenomenon is called
Extragenic or intergenic suppression reveals the effect of a mutation in a gene at a different place within the genome.
It can be explained as a mutation disrupting the complementary interaction between protein molecules which can be compensated by a second mutation occuring at some place in the genome restoring or providing a suitable alternative interaction between those molecules.
Suppose, evolution on earth had occurred in such a way that there are 96 amino acids instead of 20. DNA has 12 different types of bases and DNA synthesis occurs in the same way as today. The minimum number of bases per DNA codon would be
If one base is coding one amino acid then (12)1 = 12, but we have 96 amino acids. Suppose two bases form one codon, then (12)2 = 144. It is sufficient to code 96 or 20 amino acids and hence two, bases form one codon.
Radioactive thymidene is fed to cells about to enter S-phase. It will make radioactive
Euchromatin replicate in early S-phase and heterochromatin in late S + G2-phase and hence, both incorporate radioactive thymidene.
What would happen, if in a gene encoding a polypeptide of 50 amino acids, 25th codon (UAU) is mutated to UAA?
If in a gene encoding a polypeptide of 50 amino acids, 25th codon (UAU) is mutated to UAA. A polypeptide of 24 amino acids will be formed. Since, UAA is a termination codon, no further polypeptide will be formed.
Okazaki is known for his contribution to the understanding of
Okazaki fragments are the small DNA fragments, which are synthesized from DNA polymerase III on the lagging strand. It is plays an important role to understand the non-conservative nature of DNA replication.
The beginning of understanding genetic transformation in bacteria was made by
The understanding of genetic transformation in bacteria was made by Frederick F Griffith.
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