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

The similarity between DNA and RNA is that both

  1. are double stranded

  2. have similar sugars

  3. are polymers of nucleotides

  4. have similar pyrimidine
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Both DNA and RNA are nucleic acids composed of nucleotide monomers, which is their fundamental similarity. The key differences are that DNA contains deoxyribose sugar and is typically double-stranded, while RNA contains ribose sugar and is usually single-stranded. DNA uses thymine as a pyrimidine base, whereas RNA uses uracil.

Multiple choice

Which base is responsible for hot spots in spontaneous point mutation?

  1. Adenine

  2. Guanine

  3. 5-bromouracil

  4. 5-methylcytocine
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

5-Bromouracil (or 5-bromo-2,4(1H,3H)-pyrimidinedione or 5-BrU or 5-BU) is a brominated derivative of uracil that acts as an antimetabolite or base analog, substituting for thymine in DNA, and can induce DNA mutation

Multiple choice

DNA also exists as modified structure known as a triple helical DNA. Which of the following does not apply to this modified form of DNA?

  1. It is formed at neutral or acidic pH although being rare.

  2. It is triple-stranded.

  3. It requires Hoogsteen hydrogen bonding only.

  4. It requires Watson-Crick hydrogen bonding.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

A triple-stranded DNA is a structure of DNA in which three oligonucleotides wind around each other and form a triple helix. One strand binds to a B-form DNA double helix through Hoogsteen or reversed Hoogsteen hydrogen bonds. The triple helix is a partial binding to one of the strands, where the other strand maintains the Watson-Crick pairing. The formation of triple helix is favoured when there are stretches of oligopurines/pyrimidines in a DNA.

Multiple choice

The DNA strands are antiparallel because of A. orientation of nitrogenous bases B. phosphodiester bonds C. orientation of sugar and phosphate molecules D. structure of the deoxyribose sugar E. hydrogen bonds

  1. B and D

  2. B, C and D

  3. Only A

  4. A, B and E
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The antiparallel nature of DNA molecule is primarily due to structure of deoxyribose sugar (it lacks an oxygen at 2') that causes the difference in chemical polarity and the directionalism of phosphodiester bonds makes the polarity zero.

Multiple choice

With reference to the properties of sugars in DNA, answer the following question.

What would be the expected change in the DNA structure if the 1' position of the deoxyribose sugar is silenced?

  1. The double helical structure will distort and bend towards right.

  2. The complete double helical structure will be destroyed.

  3. The stack space will be highly decreased thus minimising the helical rise.

  4. There would not be a visible change in the structure although physico-chemical properties would be affected.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The deoxyribose sugar has an 'H' instead of 'OH' at 2' position. The nitrogenous bases binds to the 1' position of the sugars by glycosidic bonds. Silencing of the 1' position will hinder the glycosidic bond formation and thereby disrupting the complete structure.

Multiple choice

DNA having labelled thymidine is allowed to replicate in medium having non-radioactive thymidine. After 3 replications, the number of DNA molecules having labelled thymidine shall be

  1. one

  2. two

  3. four

  4. eight

Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Initially we have 2 strands with radioactive thymidine. Going by the concept of replication and the statement provided that the replications were carried out in non-radioactive medium, there would be 2 molecules of DNA having radioactive thymidine.

Multiple choice

With reference to the properties of sugars in DNA, fill in the blanks.

The ribose sugar and deoxyribose sugar are ____ carbon sugars and they both differ in an oxygen (O) at ___ position.

  1. 5; 1'

  2. 6; 3'

  3. 6; 2'

  4. 5; 2'
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The deoxyribose sugar has an 'H' instead of 'OH' at 2' position. The nitrogenous bases bind to the 1' position of the sugars by glycosidic bonds. Silencing of the 1' position will hinder the glycosidic bond formation and thereby disrupting the complete structure.

Multiple choice

Which of the following statements is/are not correct about deoxyribonucleic acid?

  1. Histones are rich in the acidic amino acid moities.
  2. A typical nucleosome contains 200 bp of DNA helix.
  3. The chromatin that is more densely packed and stains dark are called as euchromatin.
  4. Euchromatin is a transcriptionally active chromatin.

  1. 1 and 2

  2. 1 and 3

  3. 1 and 4

  4. 2 and 3

  5. 3 and 4
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

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. In a typical nucleus, some region of chromatin are loosely packed (and stains light) and are referred to as euchromatin. The chromatin that is more densely packed and stains dark are called as Heterochromatin.

Multiple choice

Which of the following statements is/are correct about the structure of deoxyribonucleic acid?

  1. It is made of two polynucleotide chains, where the backbone is constituted by sugar-phosphate, and the bases project outside.
  2. The two chains have anti-parallel polarity.
  3. Adenine forms three hydrogen bonds with thymine from opposite strand.
  4. The two chains are coiled in a right-handed fashion.

  1. 1 and 2

  2. 1 and 4

  3. 2 and 3

  4. 2 and 4

  5. 3 and 4
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The two chains have anti-parallel polarity. It means, if one chain has the polarity 5'→3', the other has 3'→5'. The two chains are coiled in a right-handed fashion. The pitch of the helix is 3.4 nm and there are roughly 10 bp in each turn. Consequently, the distance between a bp in a helix is approximately equal to 0.34 nm.

Multiple choice

The International Nucleotide Sequence Database (INSD) consists of which of the following databases?

  1. DNA Data Bank of Japan
  2. European Nucleotide Archive
  3. GenBank
  4. PROSITE
  5. VectorBase

  1. 1, 2 and 3

  2. 1, 3 and 5

  3. 2, 3 and 4

  4. 2, 4 and 5

  5. 3, 4 and 5
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The International Nucleotide Sequence Database Collaboration (INSDC) is a joint effort to collect and disseminate databases containing DNA and RNA sequences. It consists of the following databases: DNA Data Bank of Japan (Japan), GenBank (USA) and the European Nucleotide Archive (UK).

Multiple choice

Which of the following is an incorrect statement?

  1. PCR is a laboratory technique for amplifying a specific DNA sequence.

  2. Gel electrophoresis is a basic technique used to separate DNA, RNA or proteins.

  3. The northern blotting is a laboratory method used to detect specific RNA molecules from a mixture of RNA molecules.

  4. Electroporation used to transfer polar molecules like DNA into host cells.

  5. The southern blotting technique depends on similarities between the sequences of probe RNA and experimental RNA.
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

The southern blotting technique is a laboratory method used to detect specific DNA molecules from many other DNA molecules. The southern blotting technique depends on similarities between the sequences of probe DNA and experimental DNA.

Multiple choice

Hybridoma is a result of fusion of

  1. normal antibody producing cell with myeloma

  2. abnormal antibody producing cell with myeloma

  3. male reproducing cell with myeloma

  4. female reproducing cell with myeloma

  5. liver cell with myeloma
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Hybridoma technology is a technology of forming hybrid cell lines (called hybridomas) by fusing a specific antibody-producing B cell with a myeloma .