Question

QUESTION 3 The codon S-AUG-3' on an mRNA encodes the amino acid methionine. What is the corresponding anticodon found on the methionine charged tRNA? 3-UAC-5 5-UAC-3 o 3-GUA-5 5'-ATG-3

Answer 1

Ans 3 : The corresponding anticodon found on the methionine- charged amino tRNA is 3'-UAC-5'.

Explanation: The start codon in all animals (eukaryotes) is AUG. This is the only nucleotide triplet codon that code for methionine. The tRNA has two ends one is 5' end containing Phosphate group and second end is 3' end having OH- group. The last 3 nucleotide in 3' end of tRNA is ACC. The adenine bind with the amino acid during translation. This is called charging of tRNA, is catalyzed by tRNA transferase or aminoacyl tRNA synthetase, specific to the tRNA. The anticodon loop of tRNA is capable to complementary to base-pairing with codon of the messenger RNA.

Ans 4:  

Spontaneous tautomers shift in a DNA base during replication: F) DNA polymerase III adds the wrong complementary nucleotide to the new strand, producing a mismatched base pair. The next round of replication makes the permanent.

Spontaneous depurination of one purine nucleotides: B) In DNA replication, DNA polymerase adds an adenine across from the gap in the DNA. The next round of reeplication makes this substitution permanent.

DNA intercalating agents such as those found in tobacco smoke: E) A DNA base is modified, removed or replaced entirely, causing mispairing in the next round of replication. This leads to substitution mutations.

Most chemical mutagens, except intercalating agents: A) Topoisomerase is unable tofunction properly, and when it makes cut in the strands these are not always repaired. This leads to a loss of nucleotides and potential frameshift mutations.

UV Radiation: D) Helix distortion due to photoproducts prevents DNA polymerase III from adding the correct nucleotide to the new strand, instead, DNA polymerase I fill in that stretch of DNA. Lack of proofreading leads to substitution.

Ionizing radiation: C) Repair of double stranded DNA breaks by non-homologous end joining results in some nucleotides being lost, producing frameshift mutations.