Chromatin appears as _______ under electron microscope.

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

• Rods
• Beads-on-string
• Spheres
• Helices
Correct Option: B  [ Beads-on-string ]

Remark: The nucleosomes give chromatin a "beads-on-string" appearance.

The packaging of chromatin at higher level requires additional set of proteins collectively referred to as _______

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

• Histones
• Non-histone chromosomal proteins
• Enzymes
• Polymers
Correct Option: B  [ Non-histone chromosomal proteins ]

Remark: NHC proteins are involved in higher-level packaging.

In a nucleus, some regions of chromatin are loosely packed and are referred to as _______

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

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

Remark: Euchromatin is loosely packed and transcriptionally active.

The chromatin that is more densely packed and stains dark is called _______

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

• Euchromatin
• Heterochromatin
• Mesochromatin
• None
Correct Option: B  [ Heterochromatin ]

Remark: Heterochromatin is densely packed and transcriptionally inactive.

_______ is transcriptionally active chromatin.

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

• Heterochromatin
• Euchromatin
• Both
• Neither
Correct Option: B  [ Euchromatin ]

Remark: Euchromatin allows transcription enzymes access to DNA.

The transformation experiments were conducted by _______ in 1928.

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

• Hershey and Chase
• Frederick Griffith
• Avery et al.
• Meselson and Stahl
Correct Option: B  [ Frederick Griffith ]

Remark: Griffith conducted the transformation experiments with Streptococcus pneumoniae.

Griffith worked with the bacterium _______

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

• Escherichia coli
• Streptococcus pneumoniae
• Bacillus subtilis
• Salmonella typhimurium
Correct Option: B  [ Streptococcus pneumoniae ]

Remark: The experiments involved S. pneumoniae strains S and R.

The S strain of Streptococcus pneumoniae produces a _______ mucous coat.

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

• Polypeptide
• Lipid
• Polysaccharide
• Protein
Correct Option: C  [ Polysaccharide ]

Remark: The S strain has a smooth polysaccharide capsule.

Mice infected with the _______ strain die from pneumonia infection.

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

• R
• S
• Heat-killed S
• Heat-killed R
Correct Option: B  [ S ]

Remark: The virulent S strain causes death in mice.

Griffith concluded that the R strain bacteria had somehow been transformed by the _______ bacteria.

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

• Living S
• Heat-killed S
• Living R
• Heat-killed R
Correct Option: B  [ Heat-killed S ]

Remark: The transforming principle came from the heat-killed S strain.