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 Multiple Choice QuestionsMultiple Choice Questions

1.

Assertion : Plasmids are double stranded extrachromosomal DNA.

Reason : Plasmids are possessed by eukaryotic cells.

  • If both assertion and reason are true and reason is the correct explanation of assertion.

  • If both the assertion and reason are true but reason is not the correct explanation of assertion

  • If assertion is true but reason is false.

  • If both the assertion and reason are false.


C.

If assertion is true but reason is false.

Plasmids are found mostly in prokaryotic cells and yeasts. They do not form a part of the normal chromosomal DNA of a cell and are capable of replicating independently. They constitute extrachromosomal DNA.


2.

Wobble hypothesis was given by

  • R.W. Holley

  • M. Nirenberg

  • H.G. Khorana

  • F.H.C. Crick


D.

F.H.C. Crick

The Wobble Hypothesis explains why multiple codons can code for a single amino acid. The triplet code is degenerate one with many codons than the number of amino acid types coded. It was given by F.H.C. Crick in 1966.


3.

Assertion : Clones are a group of organisms of identical genotype, produced by a single parent through asexual means.

Reason : Clones exhibit high genetic variations.

  • If both assertion and reason are true and reason is the correct explanation of assertion.

  • If both the assertion and reason are true but reason is not the correct explanation of assertion.

  • If assertion is true but reason is false

  • If both the assertion and reason are false.


C.

If assertion is true but reason is false

A clone can be defined as an individual organism that was grown from a single body cell of its parent and that is genetically identical to it. Plants that are able to propagate by asexual means produce genetically identical plants that are clones. Many unicellular organisms, such as bacteria and yeasts, are clones of parent cells generated by either binary fission or budding. The body cells of plants and animals are clones ultimately derived from the mitosis (cell reproduction) of a single fertilized egg. More narrowly, a clone can be defined as an individual organism that was grown from a single body cell of its parent and that is genetically identical to it.


4.

In RNA thymine is replaced by

  • uracil

  • adenine

  • thiamine

  • guanine


A.

uracil

In RNA, thymine is replaced by uracil. Guanine and Adenine are purines whereas Thymine and Cytosine are pyrimidines. In DNA, thymine is present instead of uracil.


5.

Extranuclear genes occurs in

  • plastids and are not inherited

  • plasmid and are not inherited

  • mitochondria and are inherited by female

  • mitochondria and are inherited by male


C.

mitochondria and are inherited by female

Cytoplasmic inheritance or non- chromosomal inheritance is the passage of traits from parents to offspring through structures present inside cytoplasm of contributing gametes. Genes controlling cytoplasmic inheritance are called plasma genes or extra nuclear genes. They occur in plastids, mitochondria, plasmids. It is usually uniparental. Also, it is known as maternal inheritsnce.


6.

Assertion : Watson and Crick provided experimental proof of semiconservative nature of DNA replication.

Reason : DNA polymerase binds nucleotides in replication.

  • If both Assertion and Reason are true and Reason is the correct explantion of Assertion

  • If both Assertion and Reason are true and Reason is not the correct explanation of Assertion

  • If Assertion is true but Reason is false

  • If Assertion is false but Reason is true.


D.

If Assertion is false but Reason is true.

Watson and Crick suggested the double helical structure of DNA. Semiconservative nature of DNA replication was proved by Messelson and Stahl by using heavy isotope of nitrogen (15N).

DNA polymerase III establishes phosphodiester linkages between the adjacent deoxyribo-nucleoside phosphate in presence of ATP/GTP, TPP and Mg2+. It produces a new strand of DNA. DNA polymerase binds nucleotides in 5'-3' direction.


7.

A point mutation comprising the substitution of a purine by pyrimidine is called

  • transition

  • translocation

  • deletion

  • transversion


D.

transversion

Transversion is a type of subsitution where a purine is replaced by a pyrimidine and vice versa.


8.

Assertion : The mRNA attaches itself to the ribosome via its 3' end.

Reason : The mRNA has F-capsular nucleotide and bases of lagging sequence.

  • If both assertion and reason are true and reason is the correct explanation of assertion.

  • If both the assertion and reason are true but reason is not the correct explanation of assertion.

  • If assertion is true but reason is false.

  • If both the assertion and reason are false.


D.

If both the assertion and reason are false.

The mRNA attaches itselfto the small subunit (30S) of the ribosome via its 5' end. This attachment is assisted by the G-cap nucleotide and bases of sequence present on the messenger RNA systems where G-cap is present as in eukaryotes.


9.

Radio-tracer technique shows that DNA is in

  • single-helix stage

  • double-helix stage

  • multi-helix stage

  • none of these


D.

none of these

DNA is a helical structure. It could be through X- ray diffractions patterns of DNA studied by Wilkins and Franklin.


10.

The chemical knifes of DNA are

  • polymerases

  • ligases

  • endonucleases

  • amylases


C.

endonucleases

A restriction enzyme or restriction endonuclease is an enzyme that cleaves DNA into fragments at or near specific recognition sites within the molecule known restriction sites.