In a transcription unit, the promoter is located towards which end of the coding strand?

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

• 3-prime end (Downstream)
• 5-prime end (Upstream)
• Middle
• Variable
Correct Option: B  [ 5-prime end (Upstream) ]

Remark: The promoter is located at the 5-prime end (upstream) of the structural gene with reference to the coding strand polarity.

Which factor binds to RNA polymerase to initiate transcription in prokaryotes?

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

• Rho factor
• Sigma factor
• Alpha factor
• Beta factor
Correct Option: B  [ Sigma factor ]

Remark: The Sigma factor binds transiently to the core RNA polymerase enzyme to recognize the promoter and initiate transcription.

Which RNA polymerase in eukaryotes is responsible for transcribing hnRNA (precursor to mRNA)?

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

• RNA Polymerase I
• RNA Polymerase II
• RNA Polymerase III
• DNA Polymerase
Correct Option: B  [ RNA Polymerase II ]

Remark: In eukaryotes, RNA Polymerase II transcribes the precursor of mRNA, which is called heterogeneous nuclear RNA (hnRNA).

What is the function of RNA Polymerase I in eukaryotes?

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

• Transcribes tRNA
• Transcribes hnRNA
• Transcribes rRNAs (28S, 18S, 5.8S)
• Transcribes 5S rRNA
Correct Option: C  [ Transcribes rRNAs (28S, 18S, 5.8S) ]

Remark: RNA Polymerase I transcribes the large ribosomal RNAs: 28S, 18S, and 5.8S rRNA. (Mnemonic: RMT -> I, II, III).

Splicing is the process of removal of _______ and joining of _______.

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

• Exons, Introns
• Introns, Exons
• Cap, Tail
• Promoter, Terminator
Correct Option: B  [ Introns, Exons ]

Remark: Splicing involves the removal of non-coding sequences called introns and the joining of coding sequences called exons to form mature mRNA.

In capping, which unusual nucleotide is added to the 5-prime end of hnRNA?

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

• Methylated Adenosine
• Methyl Guanosine Triphosphate
• Poly-A
• Uracil
Correct Option: B  [ Methyl Guanosine Triphosphate ]

Remark: During processing, a cap consisting of 7-methyl guanosine triphosphate is added to the 5-prime end of the hnRNA.

Which scientist proposed that the genetic code is a triplet?

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

• Watson
• Crick
• George Gamow
• Nirenberg
Correct Option: C  [ George Gamow ]

Remark: Physicist George Gamow argued that since there are 4 bases and 20 amino acids, the code must constitute a combination of at least 3 bases (4^3 = 64) to code for all amino acids.

Who synthesized RNA molecules with defined combinations of bases (homopolymers/copolymers) to decipher the genetic code?

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

• Har Gobind Khorana
• Marshall Nirenberg
• Watson and Crick
• Meselson
Correct Option: A  [ Har Gobind Khorana ]

Remark: Har Gobind Khorana developed a chemical method to synthesize RNA molecules with defined base combinations (like UUUUU... or UGUGUG...) to help decipher the genetic code.

The codon AUG has dual functions. It codes for _______ and acts as an _______ codon.

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

• Valine, Stop
• Methionine, Initiator
• Phenylalanine, Initiator
• Methionine, Terminator
Correct Option: B  [ Methionine, Initiator ]

Remark: AUG is the start or initiator codon and specifically codes for the amino acid Methionine.

The property of the genetic code where one amino acid is coded by more than one codon is called?

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

• Universality
• Degeneracy
• Ambiguity
• Colinearity
Correct Option: B  [ Degeneracy ]

Remark: Degeneracy refers to the fact that some amino acids are coded for by more than one triplet codon (e.g., Serine has 6 codons).