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

Arrange the following organisms in increasing order of genome size.

  1. Borrelia burgdorferi 2. Helicobacter pylori 3. Mycoplasma pneumoniae 4. Treponema pallidum

  1. 1 < 2 < 3 < 4

  2. 1 < 3 < 2 < 4

  3. 2 < 4 < 1 < 3

  4. 3 < 4 < 1 < 2

  5. 3 < 1 < 4 < 2
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Organism (Genome size in millions of nucleotide pairs): Mycoplasma pneumoniae (0.8) Treponema pallidum (1.1) Borrelia burgdorferi (1.3)  Helicobacter pylori (1.7) Hence, the correct order is 3 < 4< 1 < 2.

 

Multiple choice

How many codons make the genetic code?

  1. 4

  2. 16

  3. 64

  4. 46

  5. 20
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

If nucleotides are arranged in units of three, the possible nucleotide combination will be 4 x 4 x 4 = 64 codons, which are more than sufficient for 20 amino acids.

Multiple choice

'A genetic code is degenerate.' What is meant by this statement?

  1. A genetic code is a triplet like UUU.

  2. There are no commas in the genetic code.

  3. Three codons are for amino acid serine.

  4. There are both initiation and termination codons.

  5. The codes are non-overlapping.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Presence of more then one codon for an amino acid is called degeneracy.

Multiple choice

Which of the following pieces of information can be derived from interrupted mating experiments?

  1. Recombinant frequency

  2. Mutation frequency

  3. Genomic mapping

  4. Gene sequence
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Interrupted mating experiments are done to determine genomic maps. It is a technique that is used to map bacterial genes by determining the sequence in which donor genes enter recipient cells. Genes are mapped by disrupting conjugation after specific time intervals.

Multiple choice

Which of the following was proved by Luria and Delbruck by fluctuation test?

  1. In bacteria, genetic mutations arise in the absence of selection.

  2. In bacteria, genetic mutations arise in response to selection.

  3. Bacteria never develop resistance to their respective phages.

  4. Mutation can be induced by an external factor.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Luria and Delbruck (1943) proved by the fluctuation test that in bacteria, genetic mutations arise in the absence of selection.

Multiple choice

DNA, or deoxyribonucleic acid, is the hereditary material in all the organisms. Which of the following compounds is used in isopycnic centrifugation for separating various types of DNA?

  1. Caesium iodide

  2. Caesium fluoride

  3. Caesium chloride

  4. Caesium bromide
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Caesium chloride is an inorganic compound with the formula CsCl. It is widely used in isopycnic centrifugation for separating various types of DNA. It is a reagent in analytical chemistry, where it is used to identify ions by the colour and morphology of the precipitate.

Multiple choice

Which of the following is a set of primary nucleic acid sequence databases?

  1. PIR, MIPS, SWISS-PROT

  2. TrEMBL, NRL-3D, EMBL

  3. EMBL, TrEMBL, GenBank

  4. EMBL, GenBank, DDBJ

  5. SWISS-PROT, EMBL, TrEMBL
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Correct answer. EMBL, GenBank and DDBJ are primary nucleic acid sequence databases. Primary database is a database that stores biomolecular sequences of proteins, nucleic acids, etc. and associated annotation information of organism, species, function, etc.

Multiple choice

Identify the incorrect option for prokaryotic cell.

  1. Size is 1 to 10 μm.

  2. Double stranded DNA is present.

  3. DNA is not associated with histone sugar.

  4. Nucleolus is 0.01 to 0.5 μm in size.

  5. Membrane bound cell organelles are absent.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Nucleolus is absent in prokaryotic cell.

Multiple choice

Regarding cancer genome sequencing, which of the following statements is INCORRECT?

  1. Cancer genome sequencing is the whole genome sequencing of a single, homogeneous or heterogeneous group of cancer cells.

  2. Cancer genome sequencing involves direct sequencing of primary tumor tissue.

  3. Cancer genome sequencing is not limited to WG sequencing.

  4. Cancers are homogeneous populations of cells.

  5. Cancer genome sequencing provides clinically relevant information in patients with rare tumor types.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Cancer genome sequencing is the whole genome sequencing of a single, homogeneous or heterogeneous group of cancer cells. It is a biochemical laboratory method for the characterisation and identification of the DNA or RNA sequences of cancer cell(s).

Multiple choice

In a solution of nucleotides, made from a ground-up segment of DNA, adenine makes up 33% of the solution. What percentage of the solution would be guanine?

  1. 17%

  2. 27%

  3. 24%

  4. 33%
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

According to Chargaff's rules, in double-stranded DNA, adenine (A) pairs with thymine (T), and guanine (G) pairs with cytosine (C). If adenine is 33%, then thymine is also 33%. This accounts for 66% of the nucleotides. The remaining 34% must be guanine + cytosine in equal proportions, so guanine is 17% and cytosine is 17%.