Which enzyme synthesizes the RNA primer required for DNA replication?

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

• DNA Polymerase
• Primase
• Ligase
• Helicase
Correct Option: B  [ Primase ]

Remark: Primase is a specialized RNA polymerase that synthesizes short RNA primers to provide a free 3-prime hydroxyl group for DNA polymerase to start synthesis.

DNA Polymerase adds nucleotides to which end of the growing strand?

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

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

Remark: DNA Polymerase can only add new nucleotides to the free 3-prime hydroxyl group of the growing DNA chain.

The lagging strand is synthesized as short segments called?

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

• Okazaki fragments
• Leading fragments
• Primers
• Introns
Correct Option: A  [ Okazaki fragments ]

Remark: Because DNA polymerase synthesizes only in the 5-to-3 direction, the lagging strand (which runs 3-to-5) must be synthesized discontinuously in short pieces called Okazaki fragments.

Which enzyme joins Okazaki fragments together?

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

• DNA Polymerase
• DNA Ligase
• Helicase
• Topoisomerase
Correct Option: B  [ DNA Ligase ]

Remark: DNA Ligase acts as a molecular glue, sealing the nicks between Okazaki fragments by forming phosphodiester bonds to create a continuous strand.

The enzyme responsible for relieving tension (supercoiling) ahead of the replication fork is?

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

• Helicase
• Topoisomerase (DNA Gyrase)
• Ligase
• Primase
Correct Option: B  [ Topoisomerase (DNA Gyrase) ]

Remark: Topoisomerase (specifically DNA Gyrase in prokaryotes) relieves the torsional strain or supercoiling generated ahead of the replication fork as the DNA unwinds.

DNA replication is described as?

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

• Conservative and Continuous
• Semi-conservative and Semi-discontinuous
• Dispersive
• Non-conservative
Correct Option: B  [ Semi-conservative and Semi-discontinuous ]

Remark: Replication is semi-conservative (one old, one new strand) and semi-discontinuous (leading strand is continuous, lagging strand is discontinuous).

The segment of DNA that participates in transcription is called?

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

• Replicon
• Transcription Unit
• Operon
• Codon
Correct Option: B  [ Transcription Unit ]

Remark: A Transcription Unit is the segment of DNA defined by a promoter, the structural gene, and a terminator that is transcribed into RNA.

The Promoter is located towards which end of the coding strand?

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

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

Remark: By convention, the position of the promoter is defined by the coding strand, and it is located at the 5-prime end (upstream) of the structural gene.

Which factor is required for the initiation of 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 to the RNA Polymerase core enzyme to enable it to recognize the promoter sequence and initiate transcription.

Which factor is required for the termination of transcription in prokaryotes?

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

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

Remark: The Rho factor binds to the RNA polymerase or the nascent RNA to facilitate the termination of transcription and release of the transcript.