How many nucleotides are found in the genome of Bacteriophage Phi X 174?

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

• 48502
• 5386
• 4.6 million
• 3.3 billion
Correct Option: B  [ 5386 ]

Remark: Bacteriophage Phi X 174 contains exactly 5386 nucleotides. This is a specific data point used to illustrate genome sizes.

What is the number of base pairs in Bacteriophage Lambda?

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

• 5386
• 48502
• 4.6 x 10^6
• 3.3 x 10^9
Correct Option: B  [ 48502 ]

Remark: Bacteriophage Lambda has a genome size of 48,502 base pairs. The calculation trick 50 - 2 = 48 can help remember this number.

Which amino acids are histones primarily composed of?

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

• Lysine and Arginine
• Glycine and Alanine
• Tryptophan and Tyrosine
• Aspartate and Glutamate
Correct Option: A  [ Lysine and Arginine ]

Remark: Histones are basic proteins rich in the basic amino acids Lysine and Arginine. These positive residues allow them to bind tightly to negative DNA.

Why is DNA negatively charged?

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

• Due to Nitrogenous bases
• Due to Phosphate groups
• Due to Deoxyribose sugar
• Due to Hydrogen bonds
Correct Option: B  [ Due to Phosphate groups ]

Remark: DNA is negatively charged and acidic primarily due to the presence of phosphate groups in its backbone, which release protons at physiological pH.

The structure formed by the wrapping of DNA around a histone octamer is called?

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

• Chromatin
• Nucleosome
• Chromosome
• Solenoid
Correct Option: B  [ Nucleosome ]

Remark: The complex of negatively charged DNA wrapped around the positively charged histone octamer is called a nucleosome.

Which histone is NOT part of the nucleosome core octamer?

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

• H2A
• H2B
• H1
• H3
Correct Option: C  [ H1 ]

Remark: The nucleosome core is an octamer made of H2A, H2B, H3, and H4 (two of each). H1 is the linker histone that seals the DNA as it enters and exits the nucleosome.

Approximately how many base pairs of DNA wrap around a histone octamer?

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

• 146 bp
• 200 bp
• 100 bp
• 50 bp
Correct Option: B  [ 200 bp ]

Remark: While the core DNA is about 146 bp, the entire nucleosome structure including the linker DNA associated with it is typically cited as containing about 200 base pairs of DNA.

Which chromatin type is transcriptionally active?

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

• Heterochromatin
• Euchromatin
• Prochromatin
• Metachromatin
Correct Option: B  [ Euchromatin ]

Remark: Euchromatin is the loosely packed, light-staining form of chromatin that allows transcription machinery access to DNA, making it transcriptionally active.

Heterochromatin is characterized by being?

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

• Loosely packed and light stained
• Densely packed and dark stained
• Transcriptionally active
• Absent in eukaryotes
Correct Option: B  [ Densely packed and dark stained ]

Remark: Heterochromatin is densely packed and stains darkly. Due to this tight packaging, it is inaccessible to transcription enzymes and is therefore transcriptionally inactive.

Which region of the chromosome is likely to contain Heterochromatin?

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

• Centromere and Telomere
• Entire length equally
• Only promoter regions
• Only coding regions
Correct Option: A  [ Centromere and Telomere ]

Remark: Heterochromatin is typically found at the centromeres and telomeres of chromosomes, providing structural stability but not coding for active proteins.