Biology

DNA and Genetics

1,095 Questions

DNA and genetics questions explore molecular biology, DNA replication, and genetic engineering techniques. These topics are essential for various competitive exams requiring a strong foundation in life sciences. Practice these questions to understand complex biological processes thoroughly.

DNA replication mechanismsGenetic engineering techniquesGene editing toolsPolymerase chain reactionDNA sequencing methods

DNA and Genetics Questions

Multiple choice

A phage sensitive strain of E. coli is grown in the environment containig DNA from phage resistant bacteria. After incubation, the sensitive strain becomes resistant. Which of the following mechanisms is responsible for this event?

  1. Transduction

  2. Transformation

  3. Conjugation

  4. Replication

  5. Translation
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Transformation is genetic alteration of a cell resulting from the direct uptake, incorporation and expression of exogenous genetic material (exogenous DNA) from its surroundings and taken up through the cell membrane(s).

Multiple choice

What must happen to bacteriophage prior to infecting a bacterium?

  1. It should reproduce to make multiple copies of the phage chromosome.

  2. It should integrate its genome into the bacterial chromosome.

  3. It should penetrate the bacterial cell wall completely.

  4. It should attach to a receptor on the bacterial cell membrane.

  5. It should undergo shrinkage in its size.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The first step in the infection of a host is attachment of the phage tail to a specific receptor on the host cell membrane. The capsid on the bacteriophage does not enter the host cell.

Multiple choice

The pol gene in retroviruses does NOT encode for

  1. RNA polymerase

  2. Integrase

  3. Reverse transcriptase

  4. Proteases

  5. Neuraminidase
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

This enzyme is involved in the production of RNA from DNA through transcription. It adds ribonucleotides to growing RNA transcripts at the 3’ end. The pol gene does not encode for NA polymerase.

Multiple choice

A protein coded by a tumour suppressor gene in humans is

  1. the protein, which helps prevent apoptosis

  2. the protein, which codes for a DNA repair enzyme

  3. the protein, which controls progression through the cell cycle

  4. the protein, which forms fractions of a growth factor signalling pathway

  5. acts in the degradation of CD4 in the endoplasmic reticulum
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Tumour suppressor genes code for proteins, which normally control progression through a cell cycle checkpoint. These genes only contribute to a cancer when both copies are mutated in a way, which produces an inactive protein product. A single mutation inactivating one gene only has no effect. They contribute to cancer because the absence of the protein product removes controls on cell division.

Multiple choice

Which of the following characterises an oncogene?

  1. In tumor cells, they are expressed at lower levels.

  2. It codes for a cell cycle control protein in a cell.

  3. It codes for a protein, which restricts the cell from apoptosis.

  4. It codes for a mutated form of a protein which creates fractions of a signal transduction pathway.

  5. It is a predominantly expressed mutation, which provides growth or survival advantage to a cell.
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

An oncogene is a mutated form of a normal cellular gene (the proto-oncogene) that codes for a protein, which is either controlled abnormally, so that it is expressed in abnormally large amounts or has gained activity. It is more active than the normal protein.

Multiple choice

Restriction endonucleases are also known as

  1. molecular glue

  2. molecular scissors

  3. molecular markers

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

Restriction endonucleases are also known as molecular scissors as they function in cutting the DNA strand.

Multiple choice

Which of the following sentences about plasmids is untrue?

  1. Plasmid is always a double-stranded DNA molecule.

  2. Plasmid is always circular.

  3. Plasmid is coated with histone protein.

  4. Plasmid does not carry any vital gene necessary for the cell.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Plasmid is naked without histone protein.