Question

29. The initiator RNA attaches at the ribosome's site. A. A B. translocon C. E DP E. O 30. Which one of the following, if missing, would usually prevent translation from starting? A. one of several exons in a mRNA B. poly-A tail C. AUG codon D. spliceosome E. RNA polymerase 31. Which of the following statements about DNA synthesis is true? A. Nucleotides are added in a random fashion to single-stranded DNA. B. DNA polymerase adds dNTP monomers in the 3 to 5 direction. C. As DNA polymerase moves along the template strand, each new nucleotide provides a 5 hydroxyl group for the next reaction to occur. D. Primers are short sequences that allow the initiation of DNA synthesis. E. RNA polymerase facilitates the production of the newly forming DNA strand 32. Which of the following statements about Okazaki fragments in E. coli is true? A. They are sealed together by the action of helicase. B. They are formed on the lagging strand of DNA C. They are synthesized in the 3 to 5' direction. D. They are deleted from the newly forming strand of DNA E. They interact only with RNA polymerases 33. Which enzyme helps to unwind DNA during DNA duplication? A transcription factors B. ligase C. tropoisomerase D. helicase E. DNA polymerase III

Answer 1

Answer 29. Correct option is (D.) which is P. The process of translation occurs on the ribosomes. The two subunits of ribosomes; large and small assemble before the translation process starts having the mRNA sequence in between the two ribosomal subunits more likely a sandwich. There are three binding positions on the ribosomes for the tRNA: A site is for incoming tRNA, P site for the initiator tRNA and E site for tRNA which leaves the ribosomes.

Answer 30. Correct option is (C.) AUG codon, AUG is the start codon without it the translation process will not proceed. Other options would be incorrect because if we talk about option (A.) translation would still proceed even if there were missing exons. Since the translation machinery reads three contiguous base pairs called codons at a time so even if a base pair is missing the machinery will read the very next base pair as the third base pair assuming the codon again. Option (B.) in prokaryotes the translation starts as soon as the RNA comes out of the nucleus(nucleoid) so, the poly-A tail isn't much needed here. Option (D.) again in prokaryotes there is no splicesome hence, the translation will proceed without it. Option (E.) Rna polymerase enzyme is required in copying DNA fragments into RNA in the transcription process, so it isn't needed in translation.

Answer 31. Option (D.) is correct. Primers are the short nucleotides which start the initiation of DNA synthesis. Primers made from primase (a form of RNA polymerase) are small (5-15 nucleotides long) threads of RNA. The RNA primers are complementary to the DNA template strand which gives DNA polymerase the starting point of the replication.

Answer 32. Option (B.) is correct. Okazaki fragments are formed on the lagging strand of the DNA. We know the two strands of the DNA are oppositely oriented and since the direction of replication is always 5' to 3' and the synthesis is continuous. There is no such continuous synthesis mechanism in the 3' to 5' direction hence its called the lagging strand forming small DNA sequences called the Okazaki fragments.

Answer 33. Option (D.) is correct. Helicase unwinds the double-stranded DNA during DNA duplication process by breaking the hydrogen bonds present between the complementary bases of both the strands. While the course of its unwinding the DNA double-strand it forms a structure called the replication fork. The replication fork is the actual area where the duplication process takes place.