Who proposed the triplet nature of the genetic code?

[Molecular-Basis-of-Inheritance] [class-xii ]

• Watson and Crick
• George Gamow
• Nirenberg
• Khorana
Correct Option: B  [ George Gamow ]

Remark: Physicist George Gamow proposed that since there are 4 bases and 20 amino acids, the code must consist of combinations of at least 3 bases (4^3=64) to cover all amino acids.

Har Gobind Khorana is known for?

[Molecular-Basis-of-Inheritance] [class-xii ]

• Discovering DNA structure
• Synthesizing RNA homopolymers/copolymers
• Discovering transformation
• Lac Operon
Correct Option: B  [ Synthesizing RNA homopolymers/copolymers ]

Remark: Khorana chemically synthesized defined RNA sequences (homopolymers like UUUUU... and copolymers) to help crack the genetic code.

tRNA is also known as?

[Molecular-Basis-of-Inheritance] [class-xii ]

• Messenger RNA
• Soluble RNA (sRNA)
• Ribosomal RNA
• Heterogeneous RNA
Correct Option: B  [ Soluble RNA (sRNA) ]

Remark: tRNA was formerly referred to as soluble RNA (sRNA) because it remains soluble in 1M NaCl solution.

The 2D structure of tRNA resembles a?

[Molecular-Basis-of-Inheritance] [class-xii ]

• Double helix
• Clover-leaf
• Inverted L
• Hairpin
Correct Option: B  [ Clover-leaf ]

Remark: The secondary (2D) structure of tRNA is depicted as a clover-leaf shape.

The 3D structure of tRNA looks like?

[Molecular-Basis-of-Inheritance] [class-xii ]

• Clover-leaf
• Inverted L
• Helix
• Sphere
Correct Option: B  [ Inverted L ]

Remark: The actual tertiary (3D) structure of tRNA is compact and resembles an inverted letter L.

Amino acids attach to which end of the tRNA?

[Molecular-Basis-of-Inheritance] [class-xii ]

• 5-prime end
• 3-prime end
• Anticodon loop
• Variable loop
Correct Option: B  [ 3-prime end ]

Remark: The amino acid acceptor arm is located at the 3-prime end of the tRNA molecule, where the specific amino acid binds.

The loop of tRNA that reads the mRNA codon is called?

[Molecular-Basis-of-Inheritance] [class-xii ]

• DHU loop
• T-psi-C loop
• Anticodon loop
• Variable loop
Correct Option: C  [ Anticodon loop ]

Remark: The anticodon loop contains a triplet sequence complementary to the mRNA codon, allowing the tRNA to recognize the code.

Which enzyme catalyzes the charging of tRNA (Aminoacylation)?

[Molecular-Basis-of-Inheritance] [class-xii ]

• Peptidyl transferase
• Aminoacyl-tRNA synthetase
• RNA Polymerase
• Ligase
Correct Option: B  [ Aminoacyl-tRNA synthetase ]

Remark: This enzyme attaches the correct amino acid to its corresponding tRNA using ATP, a process called charging or aminoacylation.

The formation of a peptide bond during translation is catalyzed by?

[Molecular-Basis-of-Inheritance] [class-xii ]

• DNA Polymerase
• Peptidyl Transferase
• Primase
• Helicase
Correct Option: B  [ Peptidyl Transferase ]

Remark: The ribosome itself (specifically the large rRNA component) acts as the enzyme peptidyl transferase to form peptide bonds between amino acids.

In prokaryotes, the ribosome binding site on mRNA is called?

[Molecular-Basis-of-Inheritance] [class-xii ]

• TATA box
• Shine-Dalgarno sequence
• Enhancer
• Cap
Correct Option: B  [ Shine-Dalgarno sequence ]

Remark: The Shine-Dalgarno sequence is a specific purine-rich sequence upstream of the start codon in prokaryotic mRNA that the small ribosomal subunit recognizes.