MCQ Bank

During transcription, RNA is synthesized using DNA as the template. The resulting mRNA carries the copied genetic information from DNA for protein synthesis.

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Q15

The coding sequence of a gene is a series of __________ nucleotide codons.

A) 4
B) 2
C) 5
D) 3

AI Explanation

The coding sequence of a gene is organized into codons, each consisting of three nucleotides. Each codon specifies an amino acid or a stop signal during translation.

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Q15

Pyrimidine consist of???

A) Heterocyclic aromatic ring structure composed of carbon and nitrogen atoms. It has a six-membered ring with two nitrogen atoms at positions 1 and 3. Examples of pyrimidines include cytosine, thymine (in DNA), and uracil (in RNA).
B)
C)
D)

AI Explanation

Pyrimidines are six-membered heterocyclic aromatic nitrogen-containing bases with two nitrogen atoms in the ring. The major biological pyrimidines are cytosine, thymine, and uracil.

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Q16

The general transcription factors help polymerase bind to the __________and melt the DNA.

A) enhancer
B) promoter
C)
D)

AI Explanation

General transcription factors help RNA polymerase recognize and bind to the promoter. They also participate in opening or melting the DNA so transcription can begin.

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Q16

Most important clue of structure of DNA before 1953

A) Erwin Chargaff
B)
C)
D)

AI Explanation

Chargaff's base-composition rules provided an important clue about DNA structure before 1953. He found that the amount of adenine approximately equals thymine and guanine approximately equals cytosine.

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Q17

Select the incorrect statement regarding spliceosomes:

A) It is believed that many of the functions of the spliceosome are performed by its RNA components rather than the proteins
B) Spliceosomes are larger in size compared to a ribosome
C) In performing even a single splicing reaction, the spliceosome hydrolyzes several molecules of ATP
D) Spliceosomes complex comprises about 150 proteins and five RNAs

AI Explanation

This statement is incorrect because the spliceosome composition is more complex and its exact protein and RNA composition is not accurately represented by this fixed description. The other statements correctly describe important features of spliceosome structure and function.

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Q17

DNA with bound histone in the eukaryotes is

A) Chromatin
B)
C)
D)

AI Explanation

In eukaryotic cells, DNA associates with histone proteins to form chromatin. This packaging allows the long DNA molecule to be compacted within the nucleus.

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Q18

During initial transcription, RNA polymerase produces and releases short RNA transcripts of_____________

A) <10 nucleotides
B) <5 nucleotides
C)
D)

AI Explanation

During initial transcription, RNA polymerase can produce and release short RNA transcripts of fewer than 10 nucleotides. This abortive initiation occurs before the polymerase successfully transitions into productive elongation.

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Q18

During DNA replication each strand serve as

A) template
B)
C)
D)

AI Explanation

During DNA replication, each parental DNA strand serves as a template for synthesis of a complementary daughter strand. This produces two DNA molecules with the same genetic information.

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Q19

TFIIE, a general transcription factor consists of_______subunits

A) 3
B) 2
C)
D)

AI Explanation

TFIIE is a general transcription factor composed of two subunits. It helps recruit and regulate TFIIH during transcription initiation by RNA polymerase II.

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Q19

Mutation is necessary evil as?

A) not all mutations give advantage to organism
B)
C)
D)

AI Explanation

Mutations generate genetic variation, which is essential for evolution, but they are not necessarily beneficial. Many mutations are neutral or harmful to the organism, making mutation a necessary but potentially damaging process.

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Q20

The introns and exons are distinguished through ______________.

A) Only 3’ splice site
B) Only 5’ splice site
C) 5’ and 3’ splice site
D) 5’ and 3’ side

AI Explanation

Introns and exons are distinguished during splicing by signals at both the 5′ and 3′ splice sites. These conserved sequences help the spliceosome accurately identify the boundaries of each intron.

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Q20

Replication machine achieves remarkably high degree of accuracy

A) proofreading mechanism
B)
C)
D)

AI Explanation

DNA replication achieves high accuracy partly through the proofreading activity of DNA polymerases. The polymerase detects incorrectly incorporated nucleotides and removes them before continuing synthesis.

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Q21

During the removal of intron, the first reaction is triggered by:

A) 2’-OH of the conserved A at the branch site
B) 5’ phosphoryl group of conserved G at the splice site
C) 2’-OH of the conserved G at the branch site
D) 3’ phosphoryl group of conserved G at the splice site

AI Explanation

The first step of pre-mRNA splicing is initiated when the 2′-OH group of the conserved branch-point adenosine attacks the phosphate at the 5′ splice site. This forms the characteristic lariat intermediate.

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Q21

The RNA AU/GC ratio was roughly.... To the DNA AT/GC ratio.

A) Similar
B)
C)
D)

AI Explanation

The AU/GC ratio of RNA was found to be roughly similar to the AT/GC ratio of the corresponding DNA. This relationship supported the idea that RNA composition reflects information encoded by DNA.

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Q22

transition from initiation to elonagation phase involves the ___________enzyme shedding most of its initiation factors

A) Pol II
B) Pol I
C)
D)

AI Explanation

The transition from initiation to elongation involves RNA polymerase II shedding many of its initiation factors. Phosphorylation of its CTD helps recruit factors required for productive elongation.

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Q22

RNA polymerase performs essentially the same reaction in all cells from bacteria to human,

A) RNA
B)
C)
D)

AI Explanation

RNA polymerase catalyzes the synthesis of RNA by adding ribonucleotides to a growing RNA strand. Although the specific polymerases and regulatory mechanisms differ among organisms, the basic chemical reaction is conserved.

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Q23

large subunit of ___________has a carboxy-terminal domain (CTD), which is referred to as the “tail”

A) Pol II
B) Pol I
C)
D)

AI Explanation

The large subunit of RNA polymerase II contains a carboxy-terminal domain (CTD), often called its tail. The CTD is extensively phosphorylated during transcription and coordinates RNA-processing and transcription factors.

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Q23

Strands of DNA are separated at the replication fork..

A) dsDNA
B)
C)
D)

AI Explanation

At the replication fork, the two strands of double-stranded DNA (dsDNA) are separated to expose their bases. Each separated strand then serves as a template for synthesis of a complementary strand.

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Q24

The branchpoint site in RNA editing, is present on ___________.

A) Introns
B) Exons
C) DNA ligase
D) Both introns and Exons

AI Explanation

The branchpoint site is located within an intron of pre-mRNA. A conserved adenosine at this site participates directly in the first transesterification reaction during intron removal.