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

Which of the following statements is/are true regarding genome?

  1. The term ‘genome’ was given by Hans Winkler.
  2. Genome size is the total number of DNA base pairs in one copy of a diploid genome.
  3. Bacteriophage MS2 was the first sequenced DNA-genome.

  1. Only 1

  2. Only 2

  3. Only 3

  4. 1 and 2

  5. 2 and 3
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

This option is correct because the term ‘genome’ was given by Hans Winkler, professor of botany at the University of Hamburg, Germany.

Multiple choice

Which of the following statements are incorrect?

P. Histones are rich in the acidic amino acid residues. Q. A typical nucleosome contains 200 bp of DNA helix. R. The chromatin that is more densely packed and stains dark is called as euchromatin. S. Euchromatin is transcriptionally active chromatin.

  1. P and Q

  2. P and R

  3. P and S

  4. Q and R

  5. Q and S
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

This option is correct because in eukaryotes, there is a set of positively charged, basic proteins called histones. Histones are rich in the basic amino acid residues, lysines and arginines, and in a typical nucleus, some region of chromatin is loosely packed (and stains light) and is referred to as euchromatin. The chromatin that is more densely packed and stains dark is called as heterochromatin.

Multiple choice

What would happen if in a gene encoding a polypeptide of 100 amino acids, the 83rd codon (UAC) is mutated to UAG?

  1. A polypeptide of 99 amino acids will form.

  2. A polypeptide of 83 amino acids will form.

  3. A polypeptide of 82 amino acid will form.

  4. A polypeptide of 17 amino acids will form.

  5. Two polypeptides of 83 and 17 amino acids respectively will form.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

A polypeptide of 82 amino acid will form. As UAG is a stop codon, it will not attach with any anticodon loop of tRNAbecause polypeptide elongation will be stopped at the 83rd position. Therefore, polypeptide chain with 82 amino acids will form.

Multiple choice

Match the viral families in group I with their characteristics in group II.

 
Group I Group II
P. Adenoviridae 1. Single-stranded RNA, + Strand, Enveloped
Q. Caliciviridae 2. Single-stranded RNA, + Strand, Non-enveloped
R. Picornaviridae 3. Double-stranded DNA, Enveloped
S. Poxviridae 4. Double-stranded DNA, Non-enveloped

  1. P - 1; Q - 2; R - 3; S - 4

  2. P - 1; Q - 3; R - 2; S - 4

  3. P - 2; Q - 1; R - 4; S - 3

  4. P - 4; Q - 1; R - 2; S - 3

  5. P - 3; Q - 2; R - 4; S - 1
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Adenoviridae is a family of non-enveloped double-stranded DNA viruses. Caliciviridae is a family of enveloped + strand single-stranded RNA viruses. Picornaviridae is a family of non-enveloped + strand single-stranded RNA viruses. Poxviridae is a family of enveloped double-stranded DNA viruses.

Multiple choice

Which of the following statements regarding nucleosomes is incorrect?

  1. They are beaded structures, each with a histone core wrapped in a left-handed super helix of DNA.

  2. The beads are linked by a DNA chain.

  3. Each contains two molecules of histones H2A, H2B, H3 and H4.

  4. The primary structure of the histones is a characteristic of the cell type and the species.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Histone proteins (H2A, H2B, H3, H4) are highly conserved across species and cell types. Their primary amino acid sequence is remarkably similar from yeast to humans, not characteristic of specific cell types.

Multiple choice

Which of the following statements are true about virusoid? P. It is a satellite nucleic acid. Q. It is a non-coding molecule. R. It is a ribozyme. S. It is a viroid with capsid.

  1. P and Q

  2. Q and R

  3. P, Q and R

  4. P, Q, R and S
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Virusoids are satellite nucleic acids that depend on helper viruses for replication. They are indeed non-coding molecules and some exhibit ribozyme activity (catalytic RNA). However, they do not have a capsid - that would distinguish them from viroids, which are also naked infectious RNA molecules.