Question

Choose the correct answer from the alternatives given :

While analysing the DNA of an organism a total number of 5386 nucleotides were found out of which the proportion of different bases were: Adenine = 29%, Guanine = 17%, Cytosine = 32%, Thymine = 17%. Considering the Chargaff's rule it can be concluded that:

• A. it is a double stranded circular DNA
• B. it is single stranded DNA
• C. it is a double stranded linear DNA
• D. no conclusion can be drawn.

Answer 1

The correct option is (B):

Explanation of the correct option:

1. ​According to the Chargaff's rule, in a double stranded DNA there is a constant ratio between adenine and guanine and cytosine and thymine.
   
2. This constant ratio is because of the base complementarity of the double stranded DNA.
   
3. Here, it is given that adenine is 29% of all bases and based on that thymine should be 29% as well, but it is given here as 17%.
   
4. This proves that the DNA that is analyzed here is a single stranded DNA as it does not follow the Chargaff's rule.
   

Final Answer: Considering the Chargaff's rule it can be concluded that it is single stranded DNA.