AP BIOLOGY

THE MOLECULAR BASIS OF INHERITANCE

STRUCTURE OF NUCLEIC ACIDS

Question [CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
If 30% of the bases in a DNA molecule are adenine, what percentage of the bases are guanine?
A
20%
B
30%
C
35%
D
70%
Explanation: 

Detailed explanation-1: -The percentage of guanine is 20%.

Detailed explanation-2: -Adenine (30%) = Thymine (30%) Guanine (20%) = Cytosine (20%) Therefore, 60% A-T and 40% C-G.

Detailed explanation-3: -Option A is correct ans Thymine −30%, Guanine −20%, Cytosine −20% (Chargaffs nitrogen base pairing rule which states that amount of Adenine is equal to Thymine and Guanine is equal to Cytosine.

Detailed explanation-4: -Thymine – 30%, Guanine – 20%, Cytosine – 20%. Chargaff’s nitrogen base pairing rule which states that amount of adenine is equal to thymine and guanine is equal to cytosine.

Detailed explanation-5: -The ratio of adenine to thymine and guanine to cytosine is always unity in a DNA molecule. The percentage of adenine in DNA isolated from human liver is observed to be 30.7% .

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