A nucleosome string viewed under an electron microscope appears as?

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

• Beads-on-string
• Double helix
• Meshwork
• Rod-like
Correct Option: A  [ Beads-on-string ]

Remark: When chromatin is viewed under an electron microscope, the nucleosomes (DNA wrapped around histone octamers) linked by spacer DNA look like "beads on a string".

What is the function of DNA Ligase?

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

• Unwinds DNA
• Synthesizes RNA primers
• Joins DNA fragments
• Removes supercoils
Correct Option: C  [ Joins DNA fragments ]

Remark: DNA Ligase catalyzes the formation of a phosphodiester bond between the 3-prime hydroxyl end of one DNA fragment and the 5-prime phosphate end of another, effectively joining nicks in the backbone.

The process of copying genetic information from one strand of DNA into RNA is termed?

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

• Replication
• Transcription
• Translation
• Transformation
Correct Option: B  [ Transcription ]

Remark: Transcription is the specific process where the genetic information stored in DNA is copied into a complementary strand of RNA by the enzyme RNA polymerase.

In a DNA double helix, the two strands are?

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

• Parallel
• Identical
• Antiparallel
• Unrelated
Correct Option: C  [ Antiparallel ]

Remark: The two strands of the DNA double helix run in opposite directions. One runs 5-prime to 3-prime, and the other runs 3-prime to 5-prime. This antiparallel orientation is essential for base pairing and replication.

Which of the following is NOT a stop codon?

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

• UAA
• UGA
• UAG
• UGG
Correct Option: D  [ UGG ]

Remark: UAA (Ochre), UAG (Amber), and UGA (Opal) are the three stop codons that signal the termination of translation. UGG is the codon for Tryptophan.

The sequence of the structural gene in the Lac operon is?

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

• Z-Y-A
• A-Y-Z
• Y-Z-A
• Z-A-Y
Correct Option: A  [ Z-Y-A ]

Remark: The structural genes in the Lac operon are arranged in the order lacZ, lacY, and lacA. Z codes for beta-galactosidase, Y for permease, and A for transacetylase.

Satellite DNA is useful in?

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

• Forensic Science
• Protein synthesis
• Organ transplantation
• Genetic Engineering
Correct Option: A  [ Forensic Science ]

Remark: Satellite DNA shows a high degree of polymorphism (VNTRs) unique to individuals. This property makes it the basis for DNA profiling or fingerprinting used in forensic science to identify individuals.

The inducer of the Lac operon is?

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

• Glucose
• Galactose
• Lactose (Allolactose)
• Fructose
Correct Option: C  [ Lactose (Allolactose) ]

Remark: Lactose (or its isomer allolactose) functions as the inducer. Its presence signals the bacteria to produce the enzymes necessary to metabolize it by binding to the repressor and inactivating it.

Which molecule is removed from the 5-prime end of hnRNA during processing?

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

• Intron
• Exon
• Cap
• None
Correct Option: D  [ None ]

Remark: During processing, nothing is removed from the 5-prime end; instead, a cap is *added*. Introns are removed from the internal sequence via splicing.

Which polymerase removes RNA primers in prokaryotes?

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

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

Remark: DNA Polymerase I has 5-prime to 3-prime exonuclease activity, which allows it to remove the RNA primers and replace them with DNA nucleotides during replication.