If a double standard DNA has 20 per cent of cytosine calculate the per cent of adenine in the DNA.
Solution and Explanation
According to Chargaff's rule the DNA molecule should have an equal ratio of pyrimidine(cytosine and thymine)and purine(adenine and guanine).
It means that the number of adenine molecules is equal to thymine molecules and the number of guanine molecules is equal to cytosine molecules.
%A=%T and %G=%C
If dsDNA has 20% of cytosine then according to the law it would have 20% of guanine.
Thus, percentage of G+C content=40%
The remainig 60% represents both A+T molecule. Since adenine and guanine are always present in equal numbers the percentage of adenine molecule is 30%.
Top Questions on Molecular Basis of Inheritance
- The RNA triplet UAG acts as a stop codon which terminates the synthesis of a polypeptide. Below is given a strand of DNA which codes for four amino acids.
In which position will an insertion of a thymine nucleotide result in the termination of translation?
DNA strand:
3′ T C C A C C C G A T G C 5′- CBSE CLASS XII - 2025
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Student to attempt either option-(A) or (B):
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OR
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- CBSE CLASS XII - 2025
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- CBSE CLASS XII - 2025
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India – Trends of Urbanisation
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Concepts Used:
Structure of DNA and RNA
DNA Structure:
Human DNA is unique and is made up of 3 billion base pairs. However, 99% of them are the same in all humans. The sequence of these bases determines what information needs to be coded that is necessary for the organism's growth and development. During the process of transcription (when DNA is replicated), a product is formed known as RNA (Ribonucleic Acid). This RNA is responsible for translating genetic information from DNA to protein followed by reading through ribosomes.
Read More: Structure of DNA
RNA Structure:
The ribonucleic acid has all the components same to that of the DNA with only 2 main differences within it. RNA has the same nitrogen bases called the adenine, Guanine, Cytosine as that of the DNA except for the Thymine which is replaced by the uracil. Adenine and uracil are considered as the major building blocks of RNA and both of them form base-pair with the help of 2 hydrogen bonds.
RNA resembles a hairpin structure and like the nucleotides in DNA, nucleotides are formed in this ribonucleic material(RNA). Nucleosides are nothing but the phosphate groups which sometimes also helps in the production of nucleotides in the DNA.
Read More: Structure of RNA