Molecular Basis of Inheritance -CBSE Class 12th NCERT Solution

Get, detailed solutions to the questions of the chapter Electromagnetic induction from NCERT textbooks

Get, detailed solutions to the questions of the chapter Molecular Basis of Inheritance from NCERT textbooks. The objective is to helping students regarding the pattern of answering the question as per the cbse latest marking provided you NCERT solutions for classes 12th math and science subjects.


Some questions of this chapter are given here

Q. Group the following as nitrogenous bases and nucleosides: Adenine, Cytidine, Thymine, Guanosine, Uracil and Cytosine.

Answer. Among the list listed above, Adenine, Thymine, Uracil and cytosine are nitrogenous bases. Cytidine and Guanine are nucleosides.

Q. If a double stranded DNA has 20 per cent of cytosine, calculate the per cent of adenine in the DNA.

Answer.Taking total number of nitrogenous base to be 100 then number of cytosine will be 20. By base pairing rule we know in DNA segments a cytosine make pairs with a guanine by 3-H bonds. So, the no. of guanine will also 20. After 20 to cytosine and 20 to guanine, 60 are left. We know adenine and thymine pairs among themselves through 2-H bonds. So, 60 will be divided among adenine and guanine equally (60? 2) = 30%. By the above calculation, it is clear that adenine amount would be 30%.

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Q. Depending upon the chemical nature of the template (DNA or RNA) and the nature of nucleic acids synthesised from it (DNA or RNA), list the types of nucleic acid polymerases.

Answer. Two types of nucleic acids are found, Deoxyribonucleic acid and ribonucleic acid. These are synthesised within the cellular machinery by specific enzymes like polymerases. Polymerases are of two types depending on the kind of nucleic acid.

a) DNA polymerases: It is a DNA dependent enzyme, along with additional enzymes. It catalyzes the polymerisation of deoxynucleotides by using DNA template. This enzyme can catalyze polymerization only in one direction from 5` to 3`. Because of this replication on strand from 3` to 5` is continuous but from 3` to 5` is discontinuous.

b) RNA polymerase: This enzyme can catalyse polymeration of RNA. They may be of different types for e.g. three types of RNA are found in bacteria, mRNA, tRNA, rRNA and these RNA are synthesized by single DNA dependent RNA polymerase. It catalyzes transcription of all three types of RNA in bacteria, which are needed in protein synthesis. In eukayotes, three RNA polymerases are present in nucleus and additional polymerases present in organelles. RNA polymerase 1 does transcription of rRNA (28s, 18s, 5.8s) RNA polymerase 2 transcribes precursor of mRNA, hnRNA and RNA polymerase 3 does transcription of tRNA, 5sRNA and snRNA.


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