Biology

Molecular Biology and Genetics

717 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 kind of mutation is induced by base analog 5-bromouracil?

  1. Insertion mutation

  2. Transversion mutation

  3. Transition mutation

  4. Deletion mutation
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

5BU induces transition mutation in DNA. When a nucleotide containing 5-bromouracil is incorporated into the DNA, it is most likely to pair with adenine. However, it can spontaneously shift into another isomer which pairs with a different nucleobase, guanine. If this happens during DNA replication, a guanine will be inserted as the opposite base analog. This results in a change in one base pair of DNA, specifically a transition mutation.

Multiple choice

Which of the following form(s) DNA cross links to induce mutation?

  1. Ochratoxin A

  2. Psoralens

  3. Ethidium bromide

  4. Bromodeoxyuridine
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Psoralens are natural compounds (furocoumarins) present in plants. They form DNA cross links to induce mutation. The crosslinking reaction by psoralens targets TA sequences intercalating in DNA and linking one base of the DNA with the one below it.

Multiple choice

Which among the following methods of sequencing DNA produces information about both identity and location of nucleotide sequences within the genome of an individual?

  1. Transposon sequencing

  2. Deep sequencing

  3. Exome sequencing

  4. Positional sequencing

  5. MicroRNA sequencing
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Positional sequencing is a method of sequencing DNA that simultaneously generates information about both identity and location of nucleotide sequences. The method involves detecting the location of sequence specific recognition events (e.g., such as hybridization of probes of known sequence) on single DNA molecules.

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. Select the correct answer using codes given below:

  1. Only 1

  2. Only 2

  3. Only 3

  4. Both 1 and 2

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

The term ‘genome’ was given by Hans Winkler, professor of botany at the University of Hamburg, Germany.

Multiple choice

Full form of DNA is

  1. deoxyribonucleic acid

  2. dioxyribonucleic acid

  3. diribonucleic acid

  4. deribonucleic acid
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

DNA stands for deoxyribonucleic acid, which is the molecule that carries genetic instructions for the development, functioning, growth, and reproduction of all known organisms. Option B is incorrect because it should be 'deoxy' not 'dioxy'. Option C is missing 'oxy' and option D is missing 'oxy' as well.

Multiple choice

Define Chromosomal DNA.

  1. Genomic DNA of prokaryotic organisms complexed with protein

  2. Genomic DNA of eukaryotic organisms complexed with protein

  3. Genomic DNA of nearly all prokaryotic and eukaryotic organisms is complexed with protein to form chromosomal DNA

  4. Single stranded RNA

  5. A fragment of DNA
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

It is the complete definition for chromosomal DNA.

Multiple choice

What is the melting temperature (Tm) of DNA?

  1. The temperature at which 50% of the DNA is melted is termed the melting temperature or Tm.

  2. The temperature at which 100% of the DNA is melted is termed the melting temperature or Tm.

  3. The temperature at which DNA starts melting is termed the melting temperature or Tm.

  4. The temperature at which DNA is denatured is termed the melting temperature or Tm.

  5. All of the above
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

This option is the correct answer. At this temperature, 50% of the DNA is melted.

Multiple choice

Explain renaturation of DNA.

  1. Formation of a stable double-stranded DNA molecule

  2. Pairing of complementary single strands of DNA in order to form a stable double stranded DNA

  3. Separation of strands of a double stranded DNA

  4. Pairing of chromosomes

  5. All of the above
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Renaturation is the process in which two complementary DNA strands pair with each other to form a stable double stranded DNA. This process occurs when the melted DNA is cooled. So, the given option is true and it is the correct answer.

Multiple choice

Explain denaturation of DNA.

  1. Separation of strands of DNA into single strands

  2. Denaturation is the separation of strands of DNA into single strands when heated to 90 degrees or above

  3. Denaturation or separation of RNA strands

  4. Denaturation or separation of DNA strands when heated to 50 degrees

  5. None of these
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

When a DNA solution is heated to 90°C or above, there will be enough kinetic energy to denature the DNA completely, causing it to separate into single strands. So, this option is true.

Multiple choice

Why is the value of Tm (melting temperature) more for some DNAs as compared with other DNAs?

  1. DNA which contains more adenine (A) and thymine (T) content will have more Tm value compared with other DNAs.

  2. Tm value increases with the cytosine and guanine content in the DNA.

  3. Greater the number of C-G pairs in the DNA, more will be its Tm value than the others which have more A-T pairs.

  4. Options (2) & (3) are correct

  5. None of these
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Yes, both the options (2) and (3) actually describe the increased Tm value for some DNAs compared with others.Hence, this option is the correct answer.

Multiple choice

What is hybridisation of nucleic acids?

  1. The pairing of radioactively labelled RNA or DNA with the complementary strand of denatured DNA

  2. Pairing of RNA with complementary denatured DNA

  3. Pairing of radioactively labelled DNA with denatured DNA

  4. Options (1), (2) and (3) are true

  5. Pairing of chromosomes
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

A strand of radioactively labelled RNA or DNA, when added to a denatured DNA preparation will act as a probe for DNA molecules to which it is complementary. This hybridisation of complementary strands of nucleic acid is very useful for isolating a specific fragment of DNA from a complex mixture. Hence, this option is the correct answer.

Multiple choice

What is Hyperchromic effect of DNA?

  1. Increase in the absorption of light at 260 nm as the DNA becomes denatured is known as Hyperchromic effect.

  2. Absorption of light at 260 nm by DNA is known as hyperchromic effect.

  3. DNA denaturation with the increase in temperature is known as hyperchromic effect.

  4. Both the options (1) and (2)

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

Denatured DNA have less constrained bases compared to stacked bases of double stranded DNA. So, the denatured DNA will show more absorption of light. Hence, this option is the correct answer.

Multiple choice

Nucleoside is composed of

  1. one pentose carbon sugar and a nitogenous base

  2. a hexose sugar and a nitogenous base

  3. one pentose carbon sugar and two nitrogenous bases

  4. two pentose sugars and one base

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

Nucleosides are composed of a five membered pentose carbon sugar (2-deoxyribose sugar in DNA and ribose in RNA) and a nitrogenous base. Hence, this option is the correct answer.