Biology

DNA and Genetics

985 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 probe is used in recombinant DNA technology and molecular diagnosis?

  1. A short, double or single-stranded DNA or RNA tagged with radioactive molecule to detect the product enzyme

  2. A short mRNA strand tagged with radioactive molecule to detect the codon sequence

  3. A short DNA strand tagged with radioactive molecule for identifying the coding and template strands

  4. A short, single-stranded DNA or RNA tagged with radioactive molecule to detect the complimentary strand

  5. A short, double DNA tagged with radioactive thimidine for recognising its corresponding complementary strand
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

A short, single-stranded DNA or RNA tagged with radioactive molecule to detect the complementary strand is called probe. A short, double DNA tagged with radioactive thimidine for recognising its corresponding complementary strand is not a probe. 

Multiple choice

Which of the following statements about proto-oncogenes is true?

  1. They are originally derived from DNA tumor viruses.

  2. Loss of function mutations tend to occur in tumor cells.

  3. Mutation underlies most cases of familial predisposition to cancer.

  4. Some are activated by gene amplification.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Proto-oncogenes are normal cellular genes that, when activated by mutation, contribute towards the malignant phenotype. Gene amplification is a mechanism of proto-oncogene activation.

Multiple choice

The length of DNA molecule greatly exceeds the dimensions of the nucleus in eukaryotic cell. How is this DNA accommodated within the little sphere of nucleus?

  1. Deletion of genes

  2. Through elimination of repetitive DNA

  3. Supercoiling of nucleosomes

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

These are the actual processes of chromosomal packing of DNA within nucleus. DNA double helix coils around Histone octamers to form nucleosomes and then the nucleosomes undergo supercoiling to produce more thicker chromatids, which is accommodated within nucleus.

Multiple choice

Which of the following plasmids is used to reduce the expression of an endogenous gene?

  1. Cloning plasmids

  2. Expression plasmids

  3. Gene knockdown plasmids

  4. Reporter plasmids

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

These plasmids are used for reducing the expression of endogenous genes. This is often attained through the expression of an shRNA while targeting the mRNA of the gene of interest. These plasmids possess promoters that can influence the expression of short RNAs.

Multiple choice

Which of the following are used as intercalating agents in chemical mutation?

  1. Acridine orange, proflavin and ethidium bromide

  2. Nitrosoguanidine, methyl methanesulfonate and ethyl methanesulfonate

  3. NAAAF

  4. Peroxides

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

Acridine orange, proflavin and ethidium bromide are flat, multiple ring molecules which react with DNA bases and insert between them. This insertion creates a stretching in the DNA duplex and the DNA polymerase is fooled into inserting an extra base opposite an intercalated molecule. The result is that intercalating agents cause frameshifts.

Multiple choice

Which of the following features is NOT true for a retrovirus?

  1. The membrane of a retrovirus contains glycoproteins, which are capable of binding to a receptor protein on a host cell.

  2. Inside the cell there are two strands of DNA that have three enzymes, protease, reverse transcriptase and integrase.

  3. Inside the cells, reverse transcriptase makes a complementary strand of DNA from the retrovirus RNA and the RNA is degraded.

  4. Inside the nucleus, the DNA is incorporated into the host cell DNA with the aid of integrase.

  5. Ribosomal units are employed to transcribe the viral mRNA into amino acid sequences that can be transformed into proteins in the RER.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

This statement is wrong. The correct statement is - Inside the cell there are two strands of RNA that have three enzymes, protease, reverse transcriptase and integrase.

Multiple choice

Which of the following pairs is incorrectly matched?

  1. Recombinant DNA technology - combining genes from different species

  2. Restriction fragments - pieces of DNA that have been cut into different lengths

  3. Genomic library - all the genes contained in one kind of organism

  4. Restriction enzymes - DNA cutting enzymes

  5. DNA fingerprinting - technique for identification of patterns that occur in DNA
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

A genomic library is a collection of cloned DNA pieces from a genome.

Multiple choice

Assertion (A): The normal role of restriction endonucleases in bacterial cells is to degrade the bacterial chromosome into small pieces during replication. Reason (R): 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. (1)

  2. (2)

  3. (3)

  4. (4)

  5. (5)
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

This option is correct because 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.