AP BIOLOGY

THE MOLECULAR BASIS OF INHERITANCE

THE SEARCH FOR INHERITABLE MATERIAL

Question [CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
Erwin Chargaff discovered what feature regarding DNA
A
The Helical structure
B
The constant ratio of the bases
C
The Sugar-Phosphate Backbone
D
The length of a strand of DNA
Explanation: 

Detailed explanation-1: -Erwin Chargaff found that in DNA, the ratios of adenine (A) to thymine (T) and guanine (G) to cytosine (C) are equal. This parity is obvious in the final DNA structure.

Detailed explanation-2: -In 1950, he discovered that the amounts of adenine and thymine in DNA were roughly the same, as were the amounts of cytosine and guanine. This later became known as the first of Chargaff’s rules. Honors awarded to him include the Pasteur Medal (1949) and the National Medal of Science (1974).

Detailed explanation-3: -In 1950, Erwin Chargaff published a paper stating that in DNA of any given species, the ratio of adenine to thymine is equal, as is the ratio of cytosine to guanine. This is known as Chargaff’s ratios and it was a crucial clue that helped solve the structure of DNA.

Detailed explanation-4: -Chargaff’s rules state that in the DNA of any species and any organism, the amount of guanine should be equal to the amount of cytosine and the amount of adenine should be equal to the amount of thymine. Further a 1:1 stoichiometric ratio of purine and pyrimidine bases (i.e., A+G=T+C ) should exist.

Detailed explanation-5: -Chargaff rule: The rule that in DNA there is always equality in quantity between the bases A and T and between the bases G and C. (A is adenine, T is thymine, G is guanine, and C is cytosine.) Named for the great Austrian-American biochemist Erwin Chargaff (1905-2002) at Columbia University who discovered this rule.

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