According to Chargaff's Rule, which of the following is true for double-stranded DNA?
A
%A = %G B
%A = %T C
%G = %T D
%C = %T
Analysis & Theory
In double-stranded DNA, adenine (A) pairs with thymine (T), so their percentages are equal.
If a DNA molecule contains 30% adenine, what percentage of guanine will it contain?
A
30% B
20% C
40% D
10%
Analysis & Theory
If A = 30%, then T = 30%. The remaining 40% must be G + C, so G = 20%.
In DNA, which bases pair with each other?
A
A–C and G–T B
A–T and G–C C
A–G and T–C D
A–U and G–C
Analysis & Theory
A pairs with T (2 hydrogen bonds), and G pairs with C (3 hydrogen bonds).
Chargaff’s Rule is not applicable to which of the following?
A
Double-stranded DNA B
Mitochondrial DNA C
Single-stranded DNA D
Nuclear DNA
Analysis & Theory
Chargaff’s Rule applies only to double-stranded DNA, not single-stranded molecules.
Which of the following base pairs is held together by 3 hydrogen bonds?
A
A–T B
G–C C
A–U D
C–T
Analysis & Theory
G–C base pairs are stronger and are held together by 3 hydrogen bonds.
If %C = 18% in a DNA molecule, what is the % of A?
A
32% B
36% C
18% D
64%
Analysis & Theory
If C = 18%, then G = 18%. Remaining 64% is A + T → A = 32%.
Which base is a purine in DNA?
A
Cytosine B
Thymine C
Adenine D
Uracil
Analysis & Theory
Purines include Adenine and Guanine. Cytosine and Thymine are pyrimidines.
Who formulated the base pairing rule that led to the discovery of DNA’s structure?
A
Watson B
Crick C
Chargaff D
Franklin
Analysis & Theory
Erwin Chargaff discovered the base ratio rule: %A = %T and %G = %C.
Which base is found only in RNA and replaces thymine?
A
Uracil B
Cytosine C
Adenine D
Guanine
Analysis & Theory
Uracil (U) is found in RNA and replaces thymine (T).
If the DNA of an organism contains 24% thymine, how much cytosine is present?
A
24% B
52% C
26% D
28%
Analysis & Theory
T = 24%, so A = 24%. Total A + T = 48%, remaining G + C = 52%, so C = 26%.