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 dna replication replication and protein synthesis nucleic acids and protein synthesis heredity biology

In bacterial DNA replication, synthesis starting from the site of origin of replication

  1. Involves RNA primers

  2. Requires telomerase

  3. Proceeds unidirectionally

  4. Moves bidirectionally
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

In circular bacterial DNA, replication begins at a single origin and proceeds in both directions simultaneously around the circle, known as bidirectional replication.

Multiple choice dna replication replication and protein synthesis nucleic acids and protein synthesis heredity biology

Choose the correct answer from the alternatives given.
A restriction enzyme breaks bonds between the

  1. base pairs of a DNA molecule

  2. sugar and phosphate components of a nucleic acid molecule

  3. base pairs of a DNA-RNA hybrid molecule.

  4. exons and introns of a DNA molecule
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Restriction enzymes are the enzymes that have the capability to cleave the phosphodiester bonds between the sugar molecule and the phosphate molecule. It has a property of cleaving DNA molecules at or near a specific sequence of bases. This is produced by certain strains of bacteria. Each restriction enzyme cleaves around a specific DNA sequence. Example: EcoR1 splices around sequence GAATTC, BamH1 cleaves around GGATCC, etc.

So, the correct option is 'sugar and phosphate components of a nucleic acid molecule'.

Multiple choice dna replication replication and protein synthesis nucleic acids and protein synthesis heredity biology

Choose the correct answers from the alternatives given :
Which enzyme catalyzes the synthesis of a new strand for a DNA molecule by linking nucleotides to the developing strand?

  1. DNA ligase

  2. DNA polymerase

  3. Single-strand binding proteins

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

DNA polymerase is an enzyme that synthesis DNA molecules from deoxyribonucleotides which are the building blocks of DNA. Each nucleotide contains a sugar molecule (deoxyribose sugar), a phosphate molecule, and any one of the nucleotides (adenine, guanine, cytosine and thymine). They basically help in DNA replication by working in pairs to form a new DNA molecule. 

So, the correct option is 'DNA polymerase'.

Multiple choice dna replication replication and protein synthesis nucleic acids and protein synthesis heredity biology

Choose the correct answers from the alternatives given :
In DNA replication, the Okazaki fragments on the lagging strand are joined together by

  1. DNA ligase

  2. DNA polymerase

  3. Primase

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

DNA ligase is an enzyme that facilitates the joining of the strands of the DNA by assisting the formation of phosphodiester bonds between two nucleotides.

DNA polymerase is an enzyme that helps in DNA replication by the formation of deoxyribonucleotides, building blocks of DNA.
Primase is an enzyme that synthesis short RNA sequences called primers that help in the initiation of DNA synthesis.
Helicase is an enzyme that helps in winding and unwinding of the double-stranded structure of the DNA.
So, the correct option is 'DNA ligase'

Multiple choice dna replication replication and protein synthesis nucleic acids and protein synthesis heredity biology

Which enzyme catalyses the synthesis of a new strand for a DNA molecule by linking nucleotides to the developing strand?

  1. RNA polymerase

  2. DNA ligase

  3. DNA polymerase

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

  • RNA polymerase helps in DNA dependent RNA synthesis. This process is known as transcription. DNA strands are used as a template to synthesize RNA molecules.
  • DNA ligase is used to join DNA segments during DNA repair or during replication (to join Okazaki fragments of the lagging strands).
  • DNA polymerase works in the pair to synthesis new strand for DNA molecule from deoxyribonucleotides. In other words, it helps in DNA dependent DNA synthesis.
  • Topoisomerase enzyme participates in overwinding or unwinding of DNA. During DNA replication or transcription, DNA becomes overwound ahead of the replication fork. It binds to DNA and cut the phosphate backbone of either one or both the DNA strands.
So, the correct option is 'DNA polymerase'.

Multiple choice dna replication replication and protein synthesis nucleic acids and protein synthesis heredity biology

Thermostable enzymes Taq and Pfu isolated from thermophilic bacteria are

  1. DNA polymerases

  2. DNA ligases

  3. Restriction endonucleases

  4. RNA polymerases
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Thermophilic bacteria that live in hot springs and hydrothermal vents. Taq polymerase and Pfu polymerase are enzymes isolated from thermophilic bacteria. These enzymes are used in polymerase chain reaction as these enzymes are able to withstand the protein-denaturing conditions (high temperature) required during polymerase chain reaction ( PCR ). 

So, the correct option is 'DNA polymerases'.

Multiple choice dna replication replication and protein synthesis nucleic acids and protein synthesis heredity biology

Select the correct match of enzyme with its related function

  1. DNA polymerase - Synthesis of DNA Strands

  2. Helicase - Unwinding of DNA helix

  3. Ligase - Joins together short DNA segments

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

DNA polymerase is the enzyme required for the addition of nucleotides into a DNA strand being synthesized from an existing strand of DNA. Helicase refers to another enzyme that functions in unwinding of the double helix structure of DNA wound around one another to result in a melted region of DNA strand to begin the replication of DNA. The joining of the short segments of DNA created during replication of the lagging strand (3' to 5') happens due to the enzyme ligase that acts as a molecular glue.

So, the correct option is 'All of these'.

Multiple choice dna replication replication and protein synthesis nucleic acids and protein synthesis heredity biology

Which of the following is known as joining enzyme or repair enzyme of DNA?

  1. Transcriptase

  2. Endonucleases

  3. Ligases

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

In molecular biology, DNA ligase is a specific type of enzyme that facilitates the joining of DNA strands together by catalyzing the formation of a phosphodiester bond. It plays a role in repairing single-strand breaks in duplex DNA in living organisms. Single-strand breaks are repaired by DNA ligase using the complementary strand of the double helix as a template, with DNA ligase creating the final phosphodiester bond to fully repair the DNA.

Therefore, the correct answer is option C.

Multiple choice dna replication replication and protein synthesis nucleic acids and protein synthesis heredity biology

Select the correct option that correctly fill the blanks i - iv
I. Less than (i) of genome represents structural genes that code for proteins.
II. Chemical substance that binds with repressor and convert it into a non-DNA binding State is (ii).
III. In prokaryotes, during replication RNA primer is removed by (iii) whereas in eukaryotes it is removed by (iv).

  1. (i) - 5%, (ii) regulator, (iii) - DNA polymerase II, (iv) - DNA polymerase $\beta$
  2. (i) - 10%, (ii) - regulator, (iii) - DNA polymerase I, (iv) - DNA polymerase $\alpha$
  3. (i) - 2%, (ii) inducer, (iii) - DNA polymerase I, (iv) - DNA polymerase $\beta$
  4. (i) - 50%, (ii) inducer, (iii) - DNA polymerase III, (iv) - DNA polymerase $\alpha$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The human genome is made of 3 billion DNA base pairs and out of them 2% only are responsible for coding for proteins and the rest may have regulatory functions. In an inducible operon such as the Lac Operon the inducer binds to the repressor to inactivate it such that the repressor can no longer bind to the operator and the gene expression can take place. DNA polymerase I (or Pol I) is an enzyme that participates in the process of prokaryotic DNA replication. This is responsible for proof reading and excising or removing off the RNA primers required for initiation of replication. DNA polymerase, beta, also known as POLB, is an enzyme present in eukaryotes involved in base excision and repair, also called gap-filling DNA synthesis.

So, the correct option is '(i) - 2%, (ii) inducer, (iii) - DNA polymerase I, (iv) - DNA polymerase  β '.