AP BIOLOGY

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THE MOLECULAR BASIS OF INHERITANCE

STRUCTURE OF NUCLEIC ACIDS

Question [CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
The research of Erwin Chargaff was essential in the discovery of the structure of DNA by Crick and Watson. Chargaff analysed the base composition of DNA from a wide range of organisms.He reported his findings using the initial letter of each base to stand for the number of that base found in an organism’s genome.A=number of adenine bases G=number of guanine basesC =number of cytosine bases T=number of thymine basesWhich of these relationships did he find within the genome of each organism he studied?
A
A = G C = T
B
A+T = C+G
C
A+G = T+C
D
A = C G = T
Explanation: 

Detailed explanation-1: -The research of Erwin Chargaff was essential in the discovery of the structure of DNA by Crick and Watson. Chargaff analysed the base composition of DNA from a wide range of organisms.

Detailed explanation-2: -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.

Detailed explanation-3: -In Watson and Crick’s model, the two strands of the DNA double helix are held together by hydrogen bonds between nitrogenous bases on opposite strands. Each pair of bases lies flat, forming a “rung” on the ladder of the DNA molecule. Base pairs aren’t made up of just any combination of bases.

Detailed explanation-4: -Five different types of trinucleotide repeats are present in the transcripts of 16 genes known to be associated with TREDs.

Detailed explanation-5: -Chargaff’s rules are important because they point to a kind of “grammar of biology”, a set of hidden rules that govern the structure of DNA. This grammar ought to reveal itself as patterns in DNA that are invariant across all species.

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