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

Which of the following statements is/are correct regarding DNA?

P. Enzyme required for removing RNA primer during DNA replication is DNA primase. Q. The enzyme DNA polymerase can work only in 5’ → 3’ direction. R. The enzyme that cuts the bonds of DNA molecule at the origin of replication is restriction endonuclease. S. The enzyme required to release the tension imposed by uncoiling of strands is DNA gyrase.

  1. P and Q

  2. P and S

  3. Q and R

  4. R and S

  5. Q and S
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Correct answer. The enzyme that cuts the bonds of DNA molecule at the origin of replication is restriction endonuclease. The enzyme required to release the tension imposed by uncoiling of strands is DNA gyrase.

Multiple choice

The primary function of DNA polymerase is to

  1. add nucleotides to the growing daughter strand

  2. seal nicks along the sugar-phosphate backbone of the daughter strand

  3. unwind the parent DNA double helix

  4. prevent reassociation of the denatured present DNA strands.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

DNA polymerase adds nucleotides to an existing nucleotide strand.

Multiple choice

In negative operon

  1. co-repressor binds with repressor

  2. co-repressor does not bind with repressor

  3. co-repressor binds with inducer

  4. cAMP have negative effect on lac operon
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

In negative (repressible) oprnon, the repressor co-repressor complex binds with the operator. The free repressor cannot bind to the operator.

Multiple choice

If the gene encoding the lac repressor is mutated so that it can no longer bind the operator, will transcription of that operon occur?

  1. Yes, but only when lactose is present

  2. No, because RNA polymerase can transcribe the genes

  3. Yes, because the operator will not be bound by repressor and RNA polymerase can transcribe the lac operon.

  4. No, because cAMP levels are low when the repressor is nonfunctional
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

If the lac repressor in non functional, it cannot bind the operator site and transcription of the lac operon will occur at all times, whether or not lactose is present.

Multiple choice

Transcriptional regulation in prokaryotes can occur by

  1. a repressor binding an operator and preventing transcription

  2. an activator binding upstream from a promoter and positively affecting transcription

  3. different promoter sequences binding RNA polymerase more highly, resulting in more effective transcriptional ignition.

  4. All of the above
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Option a refers to the lac and trp repressors, option b to the CRP protein, and option c refers to prometer that have different transcriptional efficiencies.

Multiple choice

The primary function of DNA polymerase is to

  1. add nucleotides to the growing daughter strand

  2. seal nicks along the sugar-phosphate backbone of the daughter strand

  3. unwind the parent DNA double helix

  4. prevent reassociation of the denatured present DNA strands.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

DNA polymerase adds nucleotides to an existing nucleotide strand.

Multiple choice

The lagging daughter strand of DNA is synthesized in what appears to be the �wrong direction. This synthesis is accomplished by

  1. ligating (connecting) short Okazaki fragments that are synthesized in short in the �right� direction

  2. primase

  3. using multiple primers and DNA polymerase I

  4. Both (a) and (b)
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Okazaki fragments are short pieces of newly synthesized DNA. The production of each of these fragments is dependent on a beginning RNA primer. The small fragments are ultimately ligated (connected) together to form the lagging strand.

Multiple choice

Work of Beadle and Tatum on Neurospora crassa proved that

  1. DNA replication is semi conservative

  2. viruses have genetic material

  3. every gene is responsible for a specific enzyme

  4. plant cells are totipotent

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

The one gene-one enzyme hypothesis is the idea that genes act through the production of enzymes, with each gene being responsible for producing a single enzyme. This affects a single step in metabolic pathway. The concept was proposed by George Beadle and Edward Tatum.

Multiple choice

What was the objective of the experiment conducted by Hershey and Chase?

  1. To characterise the transforming principle responsible for the transformation phenomenon first described in Griffith's experiment of 1928

  2. To find whether genetic material was DNA or protein

  3. To prove that replication of DNA is semi-conservative

  4. To show that DNA is the genetic material in a bacteriophage
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The main objective of Hershey-Chase experiment was to confirm that genetic material is DNA, not protein.

Multiple choice

Which of the following statements are NOT true?

A. Plasmids are circular pieces of double stranded DNA that exist separately from chromosomal DNA. B. Plasmids that can be propagated in cells of two or more different species are called expression vectors. C. Shuttle vectors cannot be used in prokaryotes. D. A cloning vector is a small piece of DNA into which a foreign DNA fragment can be inserted for cloning purposes.

  1. A and B

  2. A and D

  3. B and C

  4. B and D

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

Correct answer. Plasmids that can be propagated in cells of two or more different species are called shuttle vectors. An expression vector is generally a plasmid that is used to introduce a specific gene into a target cell. A shuttle vector is a vector that can propagate in two different host species. Hence, inserted DNA can be tested or manipulated in two different cell types. It can be used in both eukaryotes as well as prokaryotes.

Multiple choice

Pneumococcus experiment proves that

  1. DNA is the genetic material

  2. bacteria undergo binary fission

  3. bacteria do not reproduce sexually

  4. at times, RNA controls the production of DNA and proteins
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Griffith's experiment on Pneumococcus suggested that DNA is the transforming principle.