Why is DNA more stable than RNA?

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

• DNA is double-stranded
• DNA lacks 2-prime OH group
• DNA contains Thymine
• All of the above
Correct Option: D  [ All of the above ]

Remark: DNA is more stable because it is double-stranded (protection), lacks the reactive 2-prime hydroxyl group found in RNA, and contains Thymine which is more stable than Uracil.

The presence of 2-prime OH in RNA makes it?

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

• Stable
• Labile and degradable
• Unreactive
• A better genetic material
Correct Option: B  [ Labile and degradable ]

Remark: The 2-prime hydroxyl group in ribose makes RNA chemically reactive and prone to hydrolysis, making it less stable (labile) than DNA.

RNA can act as a catalyst. Such RNA molecules are called?

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

• Enzymes
• Ribozymes
• Proteins
• Primers
Correct Option: B  [ Ribozymes ]

Remark: RNA molecules that possess catalytic activity, behaving like enzymes, are termed Ribozymes (e.g., 23S rRNA).

The "RNA World" hypothesis suggests that?

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

• DNA evolved first
• Proteins evolved first
• RNA evolved first
• Lipids evolved first
Correct Option: C  [ RNA evolved first ]

Remark: The hypothesis posits that RNA was the first genetic material because it can both store genetic information and catalyze chemical reactions essential for life.

Meselson and Stahl used which organism for their experiment?

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

• Streptococcus pneumoniae
• E. coli
• Bacteriophage
• Vicia faba
Correct Option: B  [ E. coli ]

Remark: Meselson and Stahl used the bacterium Escherichia coli (E. coli) to demonstrate the semi-conservative nature of DNA replication.

In the Meselson-Stahl experiment, N-15 is distinguished from N-14 by?

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

• Radioactivity
• Color
• Density
• Charge
Correct Option: C  [ Density ]

Remark: N-15 is a heavy isotope, not a radioisotope. It is distinguished from the lighter N-14 based on density differences using Cesium Chloride density gradient centrifugation.

After one generation of replication in N-14 medium, E. coli DNA originally grown in N-15 showed?

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

• Only heavy density
• Only light density
• Hybrid (Intermediate) density
• Mixed densities
Correct Option: C  [ Hybrid (Intermediate) density ]

Remark: After one generation, the DNA consisted of one old heavy strand (N-15) and one new light strand (N-14), resulting in a hybrid or intermediate density.

Taylor used radioactive thymidine to prove semi-conservative replication in?

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

• E. coli
• Vicia faba (Faba beans)
• Drosophila
• Humans
Correct Option: B  [ Vicia faba (Faba beans) ]

Remark: Taylor and colleagues used radioactive thymidine on the root tips of Vicia faba (faba beans) to show that eukaryotic chromosomes also replicate semi-conservatively.

The enzyme DNA Helicase is responsible for?

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

• Joining DNA fragments
• Unwinding the DNA helix
• Synthesizing RNA primers
• Proofreading
Correct Option: B  [ Unwinding the DNA helix ]

Remark: Helicase unzips or unwinds the DNA double helix by breaking the hydrogen bonds between the nitrogenous bases.

Single Stranded Binding (SSB) proteins function to?

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

• Synthesize DNA
• Stabilize single-stranded DNA
• Form primers
• Cut DNA
Correct Option: B  [ Stabilize single-stranded DNA ]

Remark: SSB proteins bind to the separated DNA strands to prevent them from re-annealing (snapping back together) and protect them from degradation.