Biology

Molecular Biology and Genetics

985 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

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

Which of the following is the protein governing the coordination of cell–cell adhesion and gene transcription in mammals?

  1. Alpha-catenin

  2. Beta-catenin

  3. Delta-2-catenin

  4. Gamma-catenin

  5. Gelsolin
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

It is a dual function protein, regulating the coordination of cell–cell adhesion and gene transcription. Mutations and overexpression of β-catenin are associated with many cancers, including hepatocellular carcinoma, colorectal carcinoma, lung cancer, malignant breast tumors, ovarian and endometrial cancer.

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

In plants, the transcription of Cab genes has been previously shown to be regulated by a circadian oscillator coupled to the red light-absorbing plant photoreceptor. Which among the following types of oscillating gene present in plants regulates the expression of CAB?

  1. Kai genes

  2. The CCA1 gene

  3. Frq gene

  4. The LHY gene

  5. Toc1 gene
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

Toc1 gene, also known as Timing of CAB Expression 1 gene, is an oscillating gene found in the plants that is known to control the expression of CAB. It has been shown to affect the period of circadian rhythms through its repression of transcription factors. This was found through mutations of toc1 in plants that had shortened period of CAB expression.

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

During the artificial peptide synthesis, the amino acids are coupled by

  1. N,N-Dicyclohexylcarbodiimide

  2. Iron(III) chloride

  3. Orthoformic acid

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

N,N-Dicyclohexylcarbodiimide is an organic whose primary use is to couple amino acids during artificial peptide synthesis. Under standard conditions, it exists in the form of white crystals with a heavy, sweet odour.

Multiple choice

Which of the following compounds suppresses racemization & enhances the efficiency of peptide synthesis?

  1. Benzotriazol-1-yl-oxytripyrrolidinophosphonium hexafluorophosphate

  2. Hydroxybenzotriazole

  3. 1-Hydroxy-7-azabenzotriazole

  4. N,N-Diisopropylcarbodiimide
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Hydroxybenzotriazole is an organic compound that is a derivative of benzotriazole. It is mainly used to suppress racemization and improve the efficiency of peptide synthesis. It is a white crystalline powder. Commercial it always contains some water (~11.7% wt as the HOBT monohydrate crystal) because it is explosive.

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.