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

If genomic sequence of the organism is done, which of the following theory will be supportive of the organism?

Directions: Rickettsia prowazekii is an obligate intracellular parasite.

  1. Parasitic bacteria have large genomes.

  2. Parasitic bacteria and viruses share similar genomic sequence.

  3. Mitochondria have evolved from endosymbiotic bacteria.

  4. Bacteria evolved from viruses.

  5. Parasitic bacterial genome has more of exons than introns.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

 Mitochondria have evolved from endosymbiotic bacteria. According to researchers, the modern mitochondria that generate energy in eukaryotic cells have actually evolved from endosymbiotic bacteria. Since these bacteria lived within cells, they have become a part of the cells producing ATP. Rickettsia prowazekii genome is very close to mitochondria.

Multiple choice

Which of the following statements is false?

  1. The term 'enzyme' was proposed by Kuhne.

  2. The first enzyme molecule to be isolated in pure crystalline form was urease.

  3. Synthesis of enzymes is regulated by inducer and repressor genes.

  4. DNA ligase was first isolated from bacteriophages.

  5. Ribozyme is RNA with enzyme activity.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Synthesis of enzymes is regulated by operator and regulator genes.

Multiple choice

Assertion: Zinc-finger nucleases (ZFNs) are artificial restriction enzymes. Reason: The DNA-binding domains of individual ZFNs are typically contained between nine and eighteen individual zinc finger repeats.

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
C Correct answer
Explanation

Zinc-finger nucleases are artificial restriction enzymes obtained by fusing a zinc finger DNA-binding domain to a DNA-cleavage domain. The DNA-binding domains of individual ZFNs are typically contained between three and six individual zinc finger repeats and can each recognise between 9 and 18 base pairs.

Multiple choice

During somatic hybridisation, which of the following enzymes are needed to obtain naked protoplasts?

  1. Cellulase and protease

  2. Cellulase and amylase

  3. Cellulase and pectinase

  4. Cellulase and lipase
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Plant cell walls contain cellulose and pectin as structural components. To obtain naked protoplasts during somatic hybridization, both cellulase (breaks down cellulose) and pectinase (breaks down pectin) are needed to digest the cell wall completely. Amylase (starch), protease (proteins), and lipase (lipids) are not relevant for cell wall digestion.

Multiple choice

How does p53 prevent the advancement of cancer in humans?

  1. It acts as a transcription factor.

  2. It restricts the replication of cells with damaged DNA.

  3. It restricts the cells from triggering apoptosis.

  4. It regulates the synthesis of DNA repair enzymes, which replaces telomeres.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

TP53 protein is normally present at very low levels in the cell because it is broken down very quickly after its synthesis. The p53 gene is a tumour suppressor gene, which is inactivated in at least 50% of all cancers. Its role is to prevent the replication of cells with damaged DNA.

Multiple choice

The protein coded by a tumour suppressor gene in humans

  1. forms fractions of a growth factor signaling pathway

  2. codes for a DNA repair enzyme

  3. helps to prevent apoptosis

  4. controls progression through the cell cycle
Reveal answer Fill a bubble to check yourself
D 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 only one gene has no effect. They contribute to cancer because the absence of the protein product removes controls on cell division.

Multiple choice

What are the chromatin like proteins present in the chromosomal DNA of endospores?

  1. SASPs

  2. HAPs

  3. Mot B

  4. MCPs

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

The core contains the spore chromosomal DNA, which is encased in chromatin like proteins known as SASPs (small acid-soluble spore proteins) that protect the spore DNA from UV radiation and heat. The core also contains normal cell structures such as ribosomes and other enzymes,  but is not metabolically active.

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? (Eukaryotic gene organisation)

  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 the nucleus. DNA double helix coils around Histone octamers to form nucleosomes and then, the nucleosomes undergo supercoiling to produce more thicker chromatids which are accommodated within the nucleus.

Multiple choice

The Act protein secreted by Listeria monocytogenes when it invades a eukaryotic cell

  1. attaches to microtubules, allowing the bacterium to move along the fibres

  2. degrades the cytoskeleton, allowing the bacterium to travel through the plasma membrane to adjacent cells

  3. depolymerises microfilaments, allowing the bacterium to move more easily in the cytoplasm

  4. polymerises actin filaments, causing the bacterium to move through the cytoplasm
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Polymerises actin filaments, causing the bacterium to move through the cytoplasm. L. monocytogenes invades the cells by polymerising actin filaments in the cytoplasm, because ActA protein is a protease enzyme and specific for actin proteins for its degradation.

Multiple choice

In drosophila development, the two maternal genes, bicoid and nanos, regulate the expression of a gap gene called 'hunch back'. Which among the following statement(s) is/are not true about these two genes?

  1. Bicoid and nanos have opposite effects on a gene called hunch back.

  2. Bicoid is a transcription factor that activates hunch back.

  3. Nanos inhibits the translation hunch back mRNA's.

  4. Bicoid is a transcription factor that inhibits hunch back.

  5. The combined effect of biocoid and nanos results in production of high levelsof hunch back protein at the anterior of the embryo and low levels towards the posterior end.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Bicoid activates hunch back at anterior ends.

Multiple choice

In which of the following cases would you assert that the virus used the host DNA to replicate?

  1. If radioactive sulfur from a bacteriophage is found in a bacterium

  2. If radioactive phosphorus from a bacteriophage is found in a bacterium

  3. If radioactive phosphorus from a bacterium is found in a bacteriophage

  4. If radioactive sulfur from a bacterium is found in a bacteriophage
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The DNA backbone comprises of phosphorus. If the radio-labelled phosphorus from a bacteriophage is found in the DNA of bacterium, it would logically prove that the bacteriophage used bacterium's machinery due to which the radio-labelled phosphorus existed in the bacterium.

Multiple choice

Match the functions of the enzymes involved in DNA replication and choose the correct option from the alternatives given below.

 
ENZYME FUNCTION
A. DNA Polymerase III I. Stabilisation of the single stranded DNA strand
B. Helicase II. Nicks and cuts the backbone and relieves the tension of unzipped strand
C. Topoisomerase III. Synthesises new strand from RNA primer
D. DNA Polymerase I IV. Joins the backbone of newly synthesised strand
E. RNA Polymerase V. Unzipping DNA double strand
F. SSBP VI. Replaces RNA with DNA
G. DNA Ligase VII. Lays down the RNA primer

  1. A - VI, B - V, C - I, D - III, E - VII, F - II, G - IV

  2. A - III, B - V, C - II, D - VI, E - VII, F - I, G - IV

  3. A - VII, B - V, C - II, D - VI, E - III, F - I, G - IV

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

Topoisomerases demarkate the cuts by nicking the phosphates in the backbone. Only DNA polymerase I has the ability to replace RNA with DNA. SSBP are single stranded binding proteins that stablise the tension of single strandedness.