Biology

Molecular Biology and Genetics

717 Questions

Molecular biology and genetics explore the structure and function of DNA, RNA, genetic mutations, and heredity. Understanding these building blocks of life is essential for most biology examinations. Review these practice questions to test your molecular genetics knowledge.

DNA structure and basesGenetic mutationsNucleic acids compositionDNA sequencing and replication

Molecular Biology and Genetics Questions

Multiple choice

Which is the peculiar feature of chemical synthesis of oligonucleotides?

  1. DNA polymerase is involved in chemical synthesis.

  2. Template is required for oligonucleotide synthesis.

  3. Synthesis of oligonucleotide in 5'-3' direction.

  4. Synthesis of oligonucleotides in 3'-5' direction.

  5. None of the above
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Chemical synthesis of oligonucleotides occur in 3'-5' direction.

Multiple choice

Melting point (Tm) of the DNA is affected by

  1. G-C content

  2. Presence of monovalent cations

  3. A-T content

  4. Both (1) and (2)

  5. All of the above
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

G-C content and presence of monovalent cations directly affect melting point of DNA.

Multiple choice

_______ leads to hyperchromic effect of DNA.

  1. Increased absorption of light

  2. Denaturation of DNA

  3. Hydrogen bonding

  4. Van der Waals force

  5. None of the above
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Denaturation of DNA leads to hyperchromic effect.

Multiple choice

Among the following ---------------- is a DNA pyrimidine nitrogen base.

  1. 5-Hydroxymethylcytosine

  2. hygrine

  3. imazapyr

  4. imidazole
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

5-Hydroxymethylcytosine is a DNA pyrimidine nitrogen base. It is formed from the DNA base cytosine by adding a methyl group and then a hydroxy group. It is important in epigenetics because the hydroxymethyl group on the cytosine can possibly switch a gene on and off.

Multiple choice

Pseudogenes, also known as noncoding DNA, are extra DNA in a genome that do not get transcribed into RNA to synthesise proteins. Which of the following statements regarding the pseudogenes is FALSE?

  1. Exact mapping of the pseudogenes onto chromosomes is extremely difficult.

  2. The absolute rate of mutation is lower in nucleus than the one occurring in mitochondria.

  3. They form a molecular record of the evolutionary history and statistics of the parental genome.

  4. Multiple pseudogenes of the same sequence are found in human genes.

  5. They are also useful to find the rate of nucleotide substitutions, DNA loss, etc.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

They form a molecular record of the evolutionary history and statistics of the parental genome.

Multiple choice

DNA damage caused by exogenous agents comes in various forms. Which of the following agents increases the rate of depurination in DNA strands?

  1. Vinyl chloride

  2. Ionising radiation

  3. High tempretures

  4. UV-A light

  5. UV-B light
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Thermal disruption at elevated temperature increases the rate of depurination (loss of purine bases from the DNA backbone) and single-strand breaks. For example, hydrolytic depurination is seen in the thermophilic bacteria, which grow in hot springs at 40-80 °C.

Multiple choice

The heterocyclic compound used in the studies of nucleic acids and proteins is

  1. oxaziridine

  2. oxirene

  3. dioxirane

  4. diazirines
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Diazirines are a class of organic molecules consisting of a carbon bound to two nitrogen atoms, which are double-bonded to each other, forming a cyclopropene-like ring. They are mainly used as carbene precursor and also in photoaffinity labelling studies of nucleic acids and proteins.

Multiple choice

When a mutation is limited to the substitution of one nucleotide pair for another, it is called a

  1. point mutation

  2. base inversion

  3. translocation

  4. sugar-phosphate deletion
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

A point mutation is a genetic mutation where only a single nucleotide base is changed, inserted, or deleted from a DNA sequence. The substitution of one nucleotide pair for another is the classic definition of a point mutation, as opposed to larger-scale mutations like translocations or deletions.

Multiple choice

Choose the correct statement.

  1. 11 base pairs are present in one turn of DNA.

  2. Anticodon occurs in transfer-RNA.

  3. Adenine is an amino acid.

  4. Distance between two strands of DNA is 15 Å.

  5. Distance between two base pairs of DNA is 34 nm.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

An anticodon is a unit made up of three nucleotides that correspond to the three bases of the codon on the mRNA. Each tRNA contains a specific anticodon triplet sequence that can base-pair to one or more codons for an amino acid.

Multiple choice

Identify the incorrectly matched pair?

  1. Adenosine: Adenine and ribose sugar

  2. Guanidine: Guanine and ribose sugar

  3. Nucleotide: Nitrogen base, sugar and phosphate

  4. Nucleoside: Pentose sugar and nitrogen base

  5. Both 2 and 4
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Guanine linked to ribose is called guanosine. Guanidine is a strongly alkaline crystalline compound formed by the oxidation of guanine.

Multiple choice

Which of the following is a purine?

  1. Adenine

  2. Cytosine

  3. Uracil

  4. Thymine

  5. None of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Purines (adenine and guanine) have a double-ring structure consisting of a pyrimidine ring fused to an imidazole ring. Pyrimidines (cytosine, thymine, and uracil) have a single six-membered ring. This structural difference is fundamental to DNA and RNA structure and affects base pairing patterns.