1. Which amino acid does AUG code for?
a) Cysteine
b) Valine
c) Glycine
d) Methionine
Explanation: AUG is a start codon and is specifies for methionine. Thus, the first amino acid to be added to the sequence is methionine. Later, this amnio acid can be removed proteolytically.
2. Find the odd one out?
a) UAA
b) UAG
c) UGA
d) AUG
Explanation: AUG is a start codon, while UAA, UAG, and UGA are stop codons. Stop codons occur at the sequence in the mRNA where the translation is to be stopped. Hence, AUG is the odd one out.
3. Which of the following codons are known as non-sense codons?
a) UGA only
b) UAG only
c) UAA only
d) UGA, UAG, and UAA
Explanation: UGA, UAG, and UAA all stop codons. Since they do not code for any amino acid they are also called non-sense codons. They don’t even have a specific tRNA.
4. What are the codons that specify the same amino acid called?
a) Stop codons
b) Start codons
c) Acronyms
d) Synonyms
Explanation: Codons that specify the same amino acid calledsynonyms. Codons are highly degenerate. E.g. Arg, Leu, and Ser are each specified by six different codons.
5. The “standard” genetic code is almost universal??
a) False
b) True
Explanation: The above statement is true because one kind of organism can accurately translate the genes for quite a different organism. But, the genetic code of some mitochondria are not standard, but they are a variant of the standard.
6. The amino acid carried by the tRNA is covalently attached to its 5’ terminal end??
a) true
b) false
Explanation: The amino acid carried by the tRNA is covalently attached to its 3’ terminal OH group. There is also a phosphate group on the 5’ terminal end. This arm is also known as the amino acid binding arm.
7. Which of the following is also known as the “adaptor” molecule??
a) hnRNA
b) rRNA
c) mRNA
d) tRNA
Explanation: tRNA carries a specific amino acid and recognizes the corresponding mRNA codon with the help of the anticodon loop. Hence, tRNA is also known as an “adaptor” molecule.
8. Almost all known tRNA can be schematically arranged in which of the following secondary structures?
a) Planar
b) Beta-sheet
c) Helical
d) Cloverleaf
Explanation: Almost all known tRNA can be schematically arranged in cloverleaf secondary structures. Moreover, a tRNA has a 5’ terminal phosphate group. Beta-sheets and helical structures are present in the secondary structure of proteins.
9. ψ is the symbol of which amino acid?
a) Psuedocytosine
b) Pseudoguanidine
c) Pseudoadenine
d) Pseudouridine
Explanation: ψ is the symbol ofpseudouridine. It is an unusual amino acid occurring in a particular loop of tRNA. Hence, the arm containing this loop is called as Tψ C or T arm.
10. Where in the structure of tRNA, occurs a site of greatest variability?
a) Anticodon loop
b) D arm
c) Tψ Cloop
d) Variable arm
Explanation: Variable arm is a site of greatest variability in the structure of tRNA. It has around 3 to 21 nucleotides. Apart from this arm, there are other arms in tRNA like amino acid acceptor arm, anticodon arm, Tψ C arm, and D arm.