BC Lec Nucleic Acids (MCQ)

Nucleic acids are unbranched polymers composed of repeating monomers called:
A) Polysaccharides
B) Nucleotides
C) Amino acids
D) Fatty acids

Correct answer: B

Which of the following stores genetic information and transmits it from one generation to another?
A) RNA
B) DNA
C) Protein
D) Lipid

Correct answer: B

The nucleic acid responsible for translating genetic information from DNA into proteins is:
A) DNA
B) RNA
C) mRNA only
D) Histone

Correct answer: B

Each nucleotide consists of which three components?
A) Monosaccharide, amino acid, phosphate group
B) Monosaccharide, nitrogen-containing base, phosphate group
C) Fatty acid, nitrogen base, monosaccharide
D) Polysaccharide, lipid, base

Correct answer: B

DNA molecules typically contain:
A) A few dozen nucleotides
B) Several hundred nucleotides
C) Several million nucleotides
D) A few thousand nucleotides

Correct answer: C

RNA molecules are usually composed of:
A) Several million nucleotides
B) A few thousand nucleotides
C) A few dozen nucleotides
D) Billions of nucleotides

Correct answer: B

In humans, DNA is organized into:
A) 22 chromosomes
B) 23 chromosomes
C) 46 chromosomes (23 pairs)
D) 92 chromosomes

Correct answer: C

The portion of DNA responsible for synthesizing a single protein is known as a:
A) Codon
B) Gene
C) Chromosome
D) Nucleoside

Correct answer: B

The monosaccharide found in RNA nucleotides is:
A) D-glucose
B) D-ribose
C) D-2-deoxyribose
D) Galactose

Correct answer: B

The monosaccharide found in DNA nucleotides is:
A) D-glucose
B) D-ribose
C) D-2-deoxyribose
D) Fructose

Correct answer: C

Which of the following bases are pyrimidines?
A) Adenine and Guanine
B) Cytosine, Uracil, Thymine
C) Adenine, Cytosine, Uracil
D) Guanine and Thymine

Correct answer: B

Which bases are present in DNA?
A) A, G, C, U
B) A, G, C, T
C) A, C, G only
D) A, G, U, T

Correct answer: B

Which bases are present in RNA?
A) A, G, C, T
B) A, G, C, U
C) A, U, T, C
D) A, G, U, T

Correct answer: B

Nucleosides derived from pyrimidine bases are named with the suffix:
A) -osine
B) -idine
C) -ase
D) -ine

Correct answer: B

ATP (adenosine triphosphate) is an example of a:
A) Monophosphate
B) Diphosphate
C) Triphosphate
D) Deoxynucleotide

Correct answer: C

Nucleic acids are polymers of nucleotides joined together by:
A) Glycosidic linkages
B) Peptide bonds
C) Phosphodiester linkages
D) Hydrogen bonds

Correct answer: C

The backbone of a polynucleotide consists of alternating:
A) Sugar and base groups
B) Sugar and phosphate groups
C) Base and phosphate groups
D) Phosphate and peptide groups

Correct answer: B

The identity and order of nitrogenous bases in a polynucleotide determine its:
A) Secondary structure
B) Primary structure
C) Tertiary structure
D) Quaternary structure

Correct answer: B

In DNA, the sequence of bases is responsible for carrying:
A) Enzymatic activity
B) Genetic information
C) Structural support
D) Energy storage

Correct answer: B

The correct way to read the sequence of a polynucleotide is from:
A) 3′ end to 5′ end
B) 5′ end to 3′ end
C) Middle to both ends
D) N-terminus to C-terminus

Correct answer: B

The DNA double helix model was first proposed by:
A) Watson and Franklin
B) Watson and Crick
C) Crick and Pauling
D) Chargaff and Franklin

Correct answer: B

The DNA double helix is stabilized primarily by:
A) Ionic bonds
B) Disulfide bonds
C) Hydrogen bonds
D) Peptide bonds

Correct answer: C

According to Chargaff’s rules, base pairing occurs as:
A) A pairs with C; G pairs with T
B) A pairs with T; G pairs with C
C) A pairs with G; T pairs with C
D) A pairs with U; G pairs with T

Correct answer: B

In DNA, the two polynucleotide strands run:
A) In parallel 5′ to 3′ directions
B) Antiparallel to each other
C) In the same orientation 3′ to 5′
D) Randomly oriented

Correct answer: B

The number of hydrogen bonds in the base pair A–T is:
A) One
B) Two
C) Three
D) Four

Correct answer: B

The number of hydrogen bonds in the base pair C–G is:
A) One
B) Two
C) Three
D) Four

Correct answer: C

A fundamental chemical difference between DNA and RNA is that DNA contains:
A) Ribose instead of deoxyribose
B) Deoxyribose instead of ribose
C) Uracil instead of thymine
D) Peptide instead of phosphate

Correct answer: B

The presence of thymine in DNA instead of uracil provides:
A) Greater energy storage capacity
B) An additional recognition signal to avoid mutations
C) A smaller molecular weight
D) Faster replication speed

Correct answer: B

DNA wraps around proteins called histones to form:
A) Nucleosomes
B) Solenoids
C) Chromatids
D) Ribosomes

Correct answer: A

During replication, the new DNA molecules each contain:
A) Two strands from the parent DNA
B) Two entirely new strands
C) One parental strand and one newly synthesized strand
D) Only RNA intermediates

Correct answer: C

The Y-shaped region that forms as two DNA strands split apart during replication is called:
A) Replication fork
B) Okazaki fragment
C) Nucleosome
D) Helicase

Correct answer: A

The order of bases on the new DNA strand is determined by:
A) Histone acetylation
B) The template strand sequence
C) DNA ligase activity
D) Ribosomal binding sites

Correct answer: B

During replication, a new phosphodiester bond forms between:
A) 5′-OH and 3′-phosphate
B) 5′-phosphate and 3′-OH
C) Two nitrogenous bases
D) Two deoxyribose sugars

Correct answer: B

Replication on the template strand occurs in which direction?
A) 5′ → 3′
B) 3′ → 5′
C) Both directions simultaneously
D) Random orientation

Correct answer: B

The strand synthesized continuously during replication is the:
A) Lagging strand
B) Leading strand
C) Okazaki fragment
D) Primer strand

Correct answer: B

The strand synthesized discontinuously in small fragments is called the:
A) Primer strand
B) Template strand
C) Lagging strand
D) Leading strand

Correct answer: C

The short fragments formed on the lagging strand during DNA replication are called:
A) Exons
B) Okazaki fragments
C) Introns
D) Nucleosomes

Correct answer: B

Acetylation of lysine residues on histones during replication has the effect of:
A) Strengthening DNA-histone interaction
B) Weakening DNA-histone interaction
C) Breaking DNA hydrogen bonds
D) Increasing base pairing

Correct answer: B

Enzymes that relax higher-order DNA supercoiling by introducing temporary breaks are:
A) Helicases
B) Ligases
C) Topoisomerases
D) Polymerases

Correct answer: C

The enzyme responsible for unwinding the double helix at the replication fork is:
A) Helicase
B) DNA ligase
C) DNA polymerase
D) Primase

Correct answer: A

Primers required to initiate DNA synthesis are composed of:
A) DNA oligonucleotides
B) RNA oligonucleotides
C) Deoxyribonucleoside diphosphates
D) Histones

Correct answer: B

The enzyme that catalyzes the polymerization of nucleotides into new DNA strands is:
A) Helicase
B) DNA polymerase
C) Ligase
D) Topoisomerase

Correct answer: B

The enzyme responsible for joining Okazaki fragments and sealing nicks is:
A) Helicase
B) DNA polymerase
C) DNA ligase
D) Primase

Correct answer: C

The BER (base excision repair) pathway begins with:
A) DNA polymerase excising the base
B) DNA glycosylase removing a damaged base
C) Helicase unwinding the DNA
D) Ligase repairing the gap directly

Correct answer: B

In base excision repair, the gap created after removal of the AP site and nucleotides is repaired by:
A) Topoisomerase and helicase
B) Primase and gyrase
C) DNA polymerase and DNA ligase
D) RNA polymerase and ribosomes

Correct answer: C