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 Multiple Choice QuestionsMultiple Choice Questions

11.

Which of the following enzymes is used to join bits of DNA?

  • Ligase

  • Primase

  • Endonuclease

  • DNA polymerase


A.

Ligase

Ligase is an enzyme that facilitates the joining of DNA strands together by catalyzing the formation of a phosphodiester bond.

Primase is an enzyme which is involved in the replication process of DNA. It is a type of RNA Polymerase. It catalyzes the synthesis of a short RNA segment called a primer complementary to a ssDNA template.

Nucleases are enzymes that cut, shorten or degrade nucleic acids. Endonucleases are enzymes which are able to break internal phosphodiester bonds within a DNA molecule.

DNA polymerases are enzymes that synthesize a new strand of DNA complementary to an existing DNA or RNA template.


12.

The arrangement of genes on chromosomes is

  • linear 

  • ovoid

  • diffused 

  • spiral


A.

linear 

According to chromosome theory, proposed by Morgan and Castle (1912), the genes showing linkage are situated on the same pair of chromosome and are arranged in a linear fashion.


13.

Polymerase chain reaction is most useful in

  • DNA synthesis

  • DNA amplification

  • protein synthesis

  • amino acid synthesis


A.

DNA synthesis

Polymerase chain reaction (PCR) is a method widely used in molecular biology to make many copies of a specific DNA segment. Using PCR, a single copy (or more) of a DNA sequence is exponentially amplified to generate thousands to millions of more copies of that particular DNA segment


14.

Given below is a diagrammatic cross section of a single loop of the human cochlea.

diagram

Which one of the following options correctly represents the names of three parts? 

  • B: Perilymph
    C: SPerilymph
    D: Secretory Cells
  • C :Endolymph
    D : Sensory hair cells
    A: Serum

  • D: Sensory hair cells 
    A: Endolymph
    B: Tectorial membrane

  • D: Sensory hair cells 
    A: Endolymph
    B: Tectorial membrane


D.

D: Sensory hair cells 
A: Endolymph
B: Tectorial membrane

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15.

Lysozyme that is present in perspiration, saliva and tears, destroys

  • certain fungi

  • certain types of bacteria

  • all viruses

  • all viruses


B.

certain types of bacteria

Lysozyme is an enzyme that breaks down bacterial cell walls and provides protection against bacterial invasion in the skin, mucous membranes and many body fluids. It is found in tears, sweat and saliva.

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16.

Which one among the following is just a cloning plasmid not an expression plasmid?

  • pBAD-18-Cam

  • pBCSK

  • pUC18

  • pET


C.

pUC18

Cloning vector is a small piece of DNA, taken from a virus, a plasmid or the cell of a higher organism that can be stably maintained in an organism. pUC 18 is the most popular E. coli cloning vector.

An expression vector or construct, is usually a plasmid or virus designed for gene expression in cells. The vector is used to introduce a specific gene into a target cell, and can commandeer the cell's mechanism for protein synthesis to produce the protein encoded by the gene.


17.

Transformation in bacteria was discovered by

  • Lederberg 

  • Griffith

  • Avery et. al

  • Tatum


B.

Griffith

Griffiths (1928), for the first time, reported transformation in bacteria and later on Avery, Mcleod and McCarthy (1944) studied it in detail.


18.

Which one of the following pairs of codons is correctly matched with their function or the signal for the particular amino acid?

  • GUU, GCU - Alanine

  • UAG, UGA - stop

  • AUG, ACG - start/ methionine

  • AUG, ACG - start/ methionine


B.

UAG, UGA - stop

The group of nucleotides that specifies one amino acid is a code word or condo. The nucleotides of mRNA are arranged as a linear sequence of codons, each London consisting of three successive nitrogenous bases. Three codons UAG, UAA and UGA are the chain stop or termination codons. They do not code for any of the amino acids.

In most organisms AUG codon is the start or initiation codon, They do not code or any of the amino acids.

In most organisms AUG codon is the start or initiation codon, ie, the polypeptide chain starts either with methionine or N-formylmethionine.

Leucine - UUA, UUG, CUU, CUC, CUA, CUG


Alanine - GUC, GCC, GCA, GCG

GUU - Valine

UCA - Serine

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19.

Shorter generation time of E. coli compared to eukaryotes may be explained on the basis of

  • shape

  • large surface : volume ratio

  • presence of cell wall

  • absence of organelles


B.

large surface : volume ratio

In unicellular organisms (bacteria, Protozoa), cells divide at very fast rate but in multicellular animals the rate of cell division is regulated by the requirement of organism as a whole.


20.

Plasmid is

  • small extrachromosomal circular self replicating DNA that can carry genes into host organism

  • bacteriophage

  • DNA found in mitochondria

  • DNA incorporated in bacterial chromosome


A.

small extrachromosomal circular self replicating DNA that can carry genes into host organism

Plasmids are additional or extrachromosomal small rings of DNA having a few useful but non-vital genes like F-factor, R-factor or Nif gene. These are self-replicating and work as a vector in genetic engineering.