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

Complementary DNA (cDNA) is

  1. the “other strand” of single-stranded DNA

  2. in no need of template for its synthesis

  3. a base sequence of the vector DNA

  4. produced by reverse transcription

  5. produced by transcription.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Complementary DNA (cDNA) is produced by reverse transcription.

Multiple choice

Which matrix is best suited for phylogenetic analysis?

  1. BLOSUM 80 and PAM 60

  2. BLOSUM 45 and PAM 80

  3. BLOSUM 65 and PAM 250

  4. BLOSUM 30 and PAM 40
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

For phylogenetic analysis of distant homologs, matrices designed for detecting remote similarities are needed. BLOSUM 65 (for moderately divergent sequences) paired with PAM 250 (for very distant relationships) provides the best balance of sensitivity and specificity for deep evolutionary comparisons. Lower BLOSUM numbers detect more distant relationships; higher PAM numbers are for more divergent sequences.

Multiple choice

For prediction of three-dimensional structure of protein, P. homology modeling tries many possible alignments Q. threading first identifies homologues R. threading evaluates many rough models S. homology modelling optimises one model

  1. Q, S

  2. P, Q

  3. R, S

  4. Q, R
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The statement asks which statements are correct. P (homology modeling tries many possible alignments) is TRUE because homology modeling must test different alignments between the target and template to find the best structural fit. Q (threading first identifies homologues) is also TRUE because threading methods search structural databases to find potential homologous templates before threading the sequence. R is false (threading doesn't evaluate many rough models - it selects templates). S is false (homology modeling doesn't just optimize one model - it explores multiple alignments).

Multiple choice

Which of the following statements is incorrect for SCOP?

  1. It stands for Structural Classification of Proteins.

  2. It is semi-automatic and hierachical classification of protein domains.

  3. It is a database which has manual classification of protein structural domains based on similarities of their amino acid sequences and three-dimensional structures.

  4. It utilises four levels of hierachical structural classification.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Statement B claims SCOP is 'semi-automatic and hierarchical' but SCOP is actually primarily manual with expert curation, not semi-automatic. Statement A is correct (Structural Classification of Proteins). Statement C is correct (manual classification based on sequence and structural similarities). Statement D is correct (four hierarchical levels: Class, Fold, Superfamily, Family). Thus B is the incorrect statement.

Multiple choice

Which of the following statements is incorrect for PDB?

  1. PDB archive contains information about experimentally determined structures of proteins, nucleic acids and complex assemblies.

  2. In this, users can perform simple and advanced searches based on annotations relating to sequence, structure and function.

  3. In this, the molecules can be visualised and analysed and can be downloaded.

  4. Data files contained in the PDB archive (ftp:// ftp.wwpodb.org) have copyright restrictions.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

PDB (Protein Data Bank) is an open-access repository for experimentally determined 3D structures of biological macromolecules. Users can freely search, visualize, analyze, and download all data files without any copyright restrictions; the data is in the public domain. The statement in option D is incorrect because PDB data has no copyright restrictions, and the URL provided is also erroneous.

Multiple choice

Consider the following statements. (a) Genes are found on chromosomes at variable positions. (b) Each gene is responsible for providing a particular trait to an organism. (c) Chemically, gene is a segment of a large poly-nucleotide molecule called DNA and RNA. Which of the above statements is/are incorrect?

  1. Only (a)

  2. Only (b)

  3. Only (c)

  4. All of the above

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

Statement (a) is incorrect. Genes are found on chromosomes at fixed, not variable positions.

Multiple choice

Which of the following statements is true for virus?

  1. They invariably contain DNA.

  2. They multiply only in the host cells.

  3. They occur only inside bacteria.

  4. They are bigger than bacteria.

  5. Their genetic material is RNA not DNA.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

This is true as they multiply only in the host cells.

Multiple choice

Radioactive adenosine is added to a medium where living mammalian tissue is cultured and the radioactive A gets incorporated into newly synthesised DNA. Which of the following types of chromatin is expected to be radioactive if cells are exposed to radioactive adenosine as soon as this enter the S phase? (Subtopic: Chromosome and Chromatin Structure)

  1. Both heterochromatin and euchromatin

  2. Only heterochromatin

  3. Neither euchromatin or heterochromatin but the nucleolus

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

As replication of DNA occurs in S-phase of cell cycle, DNA of both euchromatin and heterochromatin will undergo replication process and they take radioactive adenosine from the medium for the formation of complementary base pairs and hence, both chromatin will show Radioactive Adenosine. Heterochromatin is densely packed and deeply stained chromatin present in the periphery of nucleus responsible for regulation of gene expression due to position effect variegation. Euchromatin is loosely packed and lightly stained chromatin present in nucleus which contains almost 92% of human genome and undergoes transcription.

Multiple choice

In case of G-protein coupled receptor (GPCR), which of the following forms of G-protein is considered to be in active state?

  1. G-protein - ADP

  2. G-protein - ATP

  3. G-protein - GDP

  4. G-protein - GTP
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

G-protein coupled receptors (GPCR) are responsible for signal transduction. GPCRs are linked to trimeric G proteins. G-proteins are GTPase switch proteins. These proteins are turned on or remained active when bound to GTP and turned off or inactivated when bound to GDP.