MCQ Bank

There are five major types of histone proteins: H1, H2A, H2B, H3, and H4. H2A, H2B, H3, and H4 form the core of the nucleosome, while H1 is the linker histone.

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Q25

The coding sequence of a gene is a series of codons that specifies the ____________ of amino acids in the polypeptide product.

A) Linear sequence
B) RNA sequence
C) Structure
D) DNA

AI Explanation

The coding sequence of a gene contains codons that specify the linear sequence of amino acids in the resulting polypeptide. This amino acid sequence forms the primary structure of the protein.

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Q25

Simplest amino acid residues

A) glycine
B)
C)
D)

AI Explanation

Glycine is the simplest amino acid because its side chain consists of only a hydrogen atom. Its small size gives it considerable flexibility within protein structures.

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Q26

The “transient excursion” model proposes transient cycles of forward and reverse translocation of__________________

A) DNA polymerase
B) RNA polymerase
C)
D)

AI Explanation

The transient excursion model describes transcription by RNA polymerase. It proposes transient forward and reverse translocation movements of RNA polymerase during the transcription cycle.

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Q26

The most common cyclobutane pyrimidine dimer is

A) thymine-thymine
B)
C)
D)

AI Explanation

The most common cyclobutane pyrimidine dimer (CPD) formed by ultraviolet radiation is the thymine-thymine dimer. It forms when adjacent thymine bases become covalently linked, distorting the DNA structure.

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Q27

There are ___________ repeats of CTD are present in the yeast Pol II

A) 27
B) 12
C)
D)

AI Explanation

Yeast RNA polymerase II contains 27 tandem repeats of its C-terminal domain (CTD) heptapeptide sequence. The CTD plays important roles in transcription regulation and RNA processing.

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Q27

Enzyme that converts hydrogen peroxide into water and oxygen is

A) catalase
B)
C)
D)

AI Explanation

Catalase is an antioxidant enzyme that decomposes hydrogen peroxide into water and oxygen. The reaction helps protect cells from oxidative damage caused by hydrogen peroxide.

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Q28

Spliceosomes are huge molecular machine that mediate _______________ reactions

A) Transesterification
B) Neutralization
C) Hydrolysis
D) High energy

AI Explanation

Spliceosomes catalyze the two transesterification reactions required to remove introns from pre-mRNA. These reactions break and reform phosphodiester bonds to produce the mature RNA.

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Q28

Nucleotides join with bond___

A) phosphodiester bond
B)
C)
D)

AI Explanation

Nucleotides in DNA and RNA are connected by phosphodiester bonds. These bonds form between the 3′ hydroxyl group of one sugar and the 5′ phosphate group of the next nucleotide.

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Q29

During elongation, the enzyme adds ______________nucleotide at a time to the growing RNA transcript

A) 5
B) 3
C) 2
D) 1

AI Explanation

During elongation, RNA polymerase adds one ribonucleotide at a time to the 3′ end of the growing RNA transcript. The sequence of added nucleotides is determined by complementary base pairing with the DNA template.

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Q29

CPD photolyase is present in a variety of organisms except _

A) placental mammals
B)
C)
D)

AI Explanation

CPD photolyase is found in many organisms, including bacteria, plants, fungi, and some animals. Placental mammals, including humans, generally lack functional CPD photolyase and instead rely mainly on nucleotide excision repair.

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Q30

RNA polymerase starts most transcripts with _____________ ribonucleotide

A) thymine
B) adenine
C)
D)

AI Explanation

RNA polymerase commonly initiates transcription with a purine, most often adenine or guanine. In the given options, adenine is the correct choice.

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Q30

Hydrolytic deamination of cytosine is estimated to take place about _ times a day in a mammalian cell.....

A) 100 to 500
B)
C)
D)

AI Explanation

Spontaneous hydrolytic deamination of cytosine occurs frequently in mammalian cells. It is estimated to occur approximately 100 to 500 times per cell per day, producing uracil from cytosine.

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Q31

TFIIH controls the ____________transition of the preinitiation complex to the open complex

A) AMP-dependent
B) ATP-dependent
C)
D)

AI Explanation

TFIIH uses ATP-dependent helicase activity to unwind promoter DNA. This helps convert the closed preinitiation complex into the open complex required for transcription initiation.

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Q31

Okazaki fragments vary in length from _ nucleotides in bacteria.

A) 1000 to 2000
B)
C)
D)

AI Explanation

Okazaki fragments are short DNA segments synthesized discontinuously on the lagging strand. In bacteria such as E. coli, they typically range from about 1000 to 2000 nucleotides.

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Q32

__________ classes of splicing found in the cell

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

AI Explanation

Two major classes of pre-mRNA splicing are recognized: spliceosomal splicing and self-splicing. Spliceosomal splicing uses small nuclear ribonucleoproteins, whereas self-splicing introns can catalyze their own removal.

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Q32

Griffith theorized that some substance of the dead bacteria might be responsible for that transformation . He called that substance as the transforming principle. _

A) TRUE
B)
C)
D)

AI Explanation

Griffith observed that nonvirulent bacteria could be transformed into virulent bacteria by material from heat-killed virulent cells. He called the unknown material responsible for this change the transforming principle.

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Q33

The 5’ splice site is recognized by:

A) U5 SnRNP
B) U2AF
C) U1 SnRNP
D) U4 SnRNP

AI Explanation

U1 snRNP recognizes and binds the 5′ splice site of pre-mRNA through base pairing between U1 snRNA and the splice-site sequence. This is an early step in spliceosome assembly.

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Q33

The RNA AU/GC ratio was roughly _ to the DNA AT/GC ratio___

A) similar
B)
C)
D)

AI Explanation

The AU/GC ratio in RNA was found to be roughly similar to the AT/GC ratio in DNA. This observation provided an early clue about the relationship between RNA and DNA composition.

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Q34

All eukaryotes have __________ types of RNA polymerases

A) 2
B) 5
C) 7
D) 3

AI Explanation

Eukaryotic cells generally have three major nuclear RNA polymerases: Pol I, Pol II, and Pol III. They specialize in transcribing different classes of RNA.