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

Genetic material in prokaryotes comprises

  1. circular DNA and histones

  2. linear DNA and histones

  3. circular DNA, but no histones

  4. linear DNA, but no histones
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Prokaryotes have circular DNA, but lack in proteins called histones.

Multiple choice

Which among the following BLAST programs are used to study the sequence-structure-function relationship of nucleotide sequences?

  1. Blastp
  2. MEGABLAST
  3. Blastn
  4. PSI-BLAST

  1. 1 and 2

  2. 1 and 3

  3. 2 and 3

  4. 2 and 4

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

Comparative sequence analysis is the first step to study sequence-structure-function relationship in protein and nucleotide sequences. E.g:  Protein sequences: Blastp, PSI-BLAST and PHI-BLAST Nucleotide sequences: MEGABLAST, Discontigous-megablast and Blastn

Multiple choice

The basis for the current treatment of urea cycle disorders is

  1. replacement of missing enzyme activity by enzyme infusion

  2. providing alternative pathways for excretion of ammonia

  3. coenzyme replacement

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

Urea cycle disorders lead to buildup of ammonia. The mainstay of current treatment is to use substances such as sodium benzoate and sodium phenylacetate to complex with ammonia, forming water soluble compounds that can be excreted in the urine.

Multiple choice

What is the sequence of nucleotides in Pribnow box?

  1. ATATTA

  2. TATAAT

  3. UAUAAT

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

The Pribnow box (also known as the Pribnow-Schaller box) is the sequence TATAAT of six nucleotides (thymine-adenine-thymine-etc.) that are essential parts of a promoter site on DNA for transcription to occur in bacteria.

Multiple choice

In a bacterial gene, the sequence TTGACA is known as

  1. pribnow box

  2. consensus sequence

  3. conservative sequence

  4. ori site

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

TTGACA is a conserved sequence seen in 35 base pair upstream of initiation site of transcription. This is known as consensus sequence.

Multiple choice

Which of the following sequences is true for prokaryotic transcription?

  1. Separation of DNA strands, joining of RNA polymerase, release of sigma factor, longation complex formation

  2. Separation of DNA strands, release of sigma factor, joining of RNA polymerase, elongation complex formation

  3. Joining of RNA polymerase, separation of DNA strands, release of sigma factor, longation complex formation

  4. Separation of DNA strands, joining of RNA polymerase, elongation complex formation, release of sigma factor

  5. Separation of DNA strands, elongation complex formation, joining of RNA polymerase, release of sigma factor

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

In prokaryotes, first DNA strands separate, then RNA polymerase adds to template DNA, then the sigma factor releases and elongation complex forms.

Multiple choice

Assertion: The normal role of restriction endonucleases in bacterial cells is to degrade the bacterial chromosome into small pieces during replication. Reason: Bacterial cells protect their own DNA from degradation by restriction endonucleases by deleting all recognition sites from the genome.

Directions: In the following question, there are two statements, Assertion (A) and Reason (R). Consider both the statements independently and mark your answer as under:

1. A and R both are correct and R is the correct explanation of A.
2. A and R both are correct and R is not the correct explanation of A.
3. A is correct and R is incorrect.
4. A is incorrect and R is correct.
5. A and R both are incorrect.

  1. A and R both are correct and R is the correct explanation of A.

  2. A and R both are correct and R is not the correct explanation of A.

  3. A is correct and R is incorrect.

  4. A is incorrect and R is correct.

  5. A and R both are incorrect.
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

Correct answer. The normal role of restriction endonucleases in bacterial cells is to degrade invading phage DNA. Bacterial cells protect their own DNA from degradation by restriction endonucleases by methylating the DNA at the sites that the enzyme recognises.

Multiple choice

Which of the following explanations about restriction endonucleases is FALSE?

  1. The enzymes are natural products of bacteria.

  2. The enzymes cut DNA at defined sequences.

  3. The enzymes cut only single-stranded DNA molecules.

  4. The enzymes are named because they restrict the growth of bacteriophage.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Restriction endonucleases cut double stranded DNA and are made by bacteria, where they cut DNA injected into the cells by bacteriophage.

Multiple choice

What happens in lac operon when glucose is present?

  1. Cyclic AMP is high, the catabolite activator protein (CAP) binds to the activator binding site and transcription of lactose is turned on.

  2. Cyclic AMP is low, CAP does not bind to the activator binding site and transcription is turned off.

  3. Cyclic AMP is low, CAP binds to the activator binding site and transcription of lactose is turned on.

  4. Cyclic AMP is high, CAP does not bind to the activator binding site and transcription of lactose is turned on.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

When glucose is present, the concentration of cyclic AMP is low, CAP is unable to bind to the activator binding site and transcription cannot take place.