Molecular Basis of Inheritance Chapter-Wise Test 6

Correct answer Carries: 4.

Wrong Answer Carries: -1.

Which of the following statements about histones is incorrect?

Histones help in DNA packaging.
Histones are negatively charged proteins.
Histones form nucleosomes with DNA.
Histones are found in eukaryotic cells.
2

Histones are **positively charged proteins**, which help in DNA packaging by binding to negatively charged DNA.

Which of the following is incorrect about post-transcriptional modifications?

Splicing removes introns from pre-mRNA.
A poly-A tail is added to the 5' end of mRNA.
A 5' cap is added to mRNA.
These modifications occur in the nucleus.
2

The **poly-A tail is added to the 3' end** of mRNA, not the 5' end.

Which of the following proteins helps in the unwinding of supercoiled DNA?

Helicase
Topoisomerase
DNA polymerase
Ligase
2

Topoisomerase relieves supercoiling tension in DNA by cutting and rejoining strands.

Which subunit of prokaryotic RNA polymerase recognizes the promoter during transcription initiation?

Alpha (α) subunit
Beta (β) subunit
Sigma (σ) factor
Omega (ω) subunit
3

The sigma (σ) factor of prokaryotic RNA polymerase recognizes the promoter and facilitates transcription initiation.

Which type of bond connects nucleotides in a single DNA strand?

Hydrogen bond
Peptide bond
Phosphodiester bond
Glycosidic bond
3

Phosphodiester bonds connect nucleotides in a DNA strand, linking the phosphate of one nucleotide to the sugar of another.

Which of the following is NOT a component of a nucleosome?

Histone proteins
DNA
RNA polymerase
Linker DNA
3

A nucleosome consists of DNA wrapped around histone proteins with linker DNA in between, but RNA polymerase is not part of it.

Which of the following correctly describes the function of enhancers?

Enhancers increase transcription by binding to activator proteins.
Enhancers directly synthesize RNA.
Enhancers repress gene expression.
Enhancers are located only within the promoter region.
1

Enhancers **increase transcription** by binding to activator proteins, which promote RNA polymerase binding.

Which protein binds to the operator region to prevent transcription in the lac operon?

RNA polymerase
Repressor protein
Activator protein
Sigma factor
2

The repressor protein binds to the operator region in the lac operon to block transcription in the absence of lactose.

Which of the following statements about transcription factors is correct?

They help regulate gene expression.
They are enzymes that synthesize RNA.
They only function in prokaryotic cells.
They are responsible for unwinding DNA during replication.
1

Transcription factors **regulate gene expression** by helping RNA polymerase bind to DNA and initiating transcription.

Which of the following statements about translation initiation is correct?

It begins at a promoter sequence.
It requires the ribosome, mRNA, and tRNA.
It occurs in the nucleus in eukaryotic cells.
It does not require energy.
2

Translation initiation **requires the ribosome, mRNA, and tRNA** to start protein synthesis.

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