In eukaryotes, RNA Polymerase I transcribes?

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

• mRNA
• tRNA
• rRNA (28S, 18S, 5.8S)
• snRNA
Correct Option: C  [ rRNA (28S, 18S, 5.8S) ]

Remark: RNA Polymerase I is responsible for transcribing the large ribosomal RNAs (28S, 18S, and 5.8S rRNA).

In eukaryotes, RNA Polymerase III transcribes?

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

• mRNA
• rRNA
• tRNA and 5S rRNA
• hnRNA
Correct Option: C  [ tRNA and 5S rRNA ]

Remark: RNA Polymerase III transcribes tRNA, 5S rRNA, and snRNAs. Mnemonic: I-rRNA, II-mRNA, III-tRNA.

The precursor of mRNA in eukaryotes is called?

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

• tRNA
• rRNA
• hnRNA
• snRNA
Correct Option: C  [ hnRNA ]

Remark: Heterogeneous nuclear RNA (hnRNA) is the primary transcript in eukaryotes that undergoes processing (splicing, capping, tailing) to become mature mRNA.

The process of removing introns and joining exons is called?

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

• Capping
• Tailing
• Splicing
• Termination
Correct Option: C  [ Splicing ]

Remark: Splicing is the post-transcriptional process where non-coding introns are removed and coding exons are joined to form a continuous coding sequence.

Which structure is responsible for splicing of hnRNA?

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

• Ribosome
• Spliceosome
• Nucleosome
• Polysome
Correct Option: B  [ Spliceosome ]

Remark: The spliceosome is a large complex of snRNAs and proteins that catalyzes the removal of introns from the primary RNA transcript.

Capping involves the addition of which nucleotide to the 5-prime end of hnRNA?

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

• Methylated Adenine
• Methylated Guanosine
• Methylated Cytosine
• Methylated Uracil
Correct Option: B  [ Methylated Guanosine ]

Remark: A 7-methylguanosine cap is added to the 5-prime end of the transcript. This protects the RNA and aids in ribosome binding.

Polyadenylation (tailing) occurs at which end of the eukaryotic mRNA?

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

• 5-prime end
• 3-prime end
• Both ends
• Introns
Correct Option: B  [ 3-prime end ]

Remark: A poly-A tail consisting of 200-300 adenylate residues is added to the 3-prime end of the mRNA, increasing stability and facilitating transport.

How many codons constitute the genetic code?

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

• 20
• 61
• 64
• 3
Correct Option: C  [ 64 ]

Remark: There are 64 possible triplet codons formed from the 4 nitrogenous bases (4^3 = 64).

Which of the following codons functions as a Start Codon?

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

• UAA
• AUG
• UGA
• UAG
Correct Option: B  [ AUG ]

Remark: AUG acts as the start codon (coding for Methionine) which initiates translation.

The property that a single amino acid is coded by more than one codon is called?

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

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

Remark: Degeneracy refers to the redundancy in the genetic code, where most amino acids are specified by more than one codon.