This set of Tricky Molecular Biology Questions and Answers focuses on “Differences Between Eukaryotic and Prokaryotic Protein Synthesis, Mistranslation in Protein Synthesis”.
1. The subunit association with the mRNA occurs before tRNA recruitment in case of both eukaryotes and prokaryotes.
Explanation: The subunit association with the mRNA occurs before tRNA recruitment only occurs in case of prokaryotic translation. In case of eukaryotes, the small subunit is already associated with an initiator tRNA when it is recruited to the capped 5’ end of the mRNA.
2. Eukaryotic mRNA generally codes for a single protein because the eukaryotic translation includes ____________
a) A single ORF
b) Monocistronic codons
c) Polycistronic codons
d) Starts at the first triplet codon
Explanation: Eukaryotic mRNA generally codes for a single protein because the eukaryotic translation includes monocistronic codons. As the tRNA ribosome complex scans the mRNA thus they begin translation as soon as they encounter the start codon.
3. The same number of auxiliary proteins is used to drive the initiation process of both prokaryotes and eukaryotes.
Explanation: Eukaryotic cells require many more auxiliary proteins to drive the initiation processes than do the prokaryotes. Remarkably, more than 30 different polypeptides are involved in initiation of translation in eukaryotes.
4. The first amino acid to be incorporated in the eukaryotic polypeptide is ___________
c) N-formyl methionine
d) N-acyl valine
Explanation: The first amino acid to be incorporated in case of prokaryotic translation is N-formyl methionine. But in case of eukaryotic translation the first amino acid to be incorporated is methionine and is represented as Met-tRNAiMet.
5. Which of the following eukaryotic proteins is an analog of IF2-GTP?
Explanation: In case of nomenclature the eukaryotic analog of IF2-GTP is eIF5B-GTP. This factor associates with the small subunit in an eIF1A-dependent manner.
6. Recognition of mRNA by 43S pre-initiation complex is mediated by the enzyme ___________
Explanation: Recognition of mRNA by 43S pre-initiation complex is mediated by the enzyme begins with the recognition of the 5’ cap found at the end of most eukaryotic mRNAs. This recognition process is mediated by the three subunit protein called eIF4F.
7. Which of the following protein interacts with the eIF4F for recruiting the pre-initiation complex to the mRNA?
Explanation: The eIF4F/B bound unstructured mRNA recruits the 43S pre-initiation complex to the mRNA. This is facilitated through the interactions between eIF4F/B and eIF3.
8. mRNA scanning is a cost effective mechanism.
Explanation: Once assembled at the 5’ end of the mRNA, the small subunit and its associated factors move along the mRNA in a 5’→3’ direction. This is an ATP dependent process that is driven by the eIF4F-associated RNA helicase.
9. The initiation factors are closely associated with the 3’ end of mRNA through the initiation between the eIF4F and the ___________
a) Poly A tail
b) Poly A binding proteins
c) Small subunit of ribosome
d) Large subunit of ribosome
Explanation: The initiation factors are closely associated with the 3’ end of mRNA through the initiation between the eIF4F and the poly A tail. This interaction is mediated by the interaction between The initiation factors are closely associated with the 3’ end of mRNA through the initiation between the eIF4F and the poly-A binding proteins that coats the poly A tail.
10. IREs for the process of translation is present in viruses. Their function resembles that of eukaryotic ribosome.
Explanation: IREs or internal ribosome entry sites are RNA sequences that function like the prokaryotic ribosome binding site. They recruit the small subunit to bind and initiate translation at an internal site in the mRNA. Thus these mRNA are polycistronic and produce a variable amount of proteins unlike the eukaryotic mechanism in which the mRNA is monocistronic and often produces a single polypeptide.
11. How many type of point mutations are able to alter the Genetic code?
Explanation: There are four types of point mutations that are able to alter the Genetic code. They are missense mutation, nonsense mutation and frame shift mutation.
12. The alterations that changes a codon specific for one amino acid to a codon specific for another amino acid is known as ___________
a) Missense mutation
b) Nonsense mutation
c) Frame shift mutation
d) Reverse Mutation
Explanation: The alterations that changes a codon specific for one amino acid to a codon specific for another amino acid is known as missense mutation. As a consequence, a gene bearing a missense mutation produces a protein product in which a single amino acid has been substituted for another.
13. Which of the following disease is caused by missense mutation?
b) Sickle cell anemia
d) Cystic fibriosis
Explanation: A classic example of a disease caused by missense mutation is sickle cell anemia. In this disease the amino acid glutamate at position 6 in the β-globin subunit of hemoglobin has been replaced with a valine.
14. Nonsense mutation is also known as ___________
a) Missense mutation
b) Frame shift mutation
c) Stop mutation
d) Reverse mutation
Explanation: Nonsense mutation is also known as stop mutation. When a nonsense mutation arises in the middle of a genetic message, an incomplete polypeptide is released from the ribosome owning to premature chain termination.
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