AP BIOLOGY

THE MOLECULAR BASIS OF INHERITANCE

STRUCTURE OF NUCLEIC ACIDS

Question [CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
During DNA replication, the two strands of a double helix separate and new nucleotides attach themselves to the original bases. What would the complementary strand be for the sequence ATTGCGAGCTG
A
CGGATACATCG
B
ATTGCGAGCTA
C
GTCGAGCGTTA
D
TAACGCTCGAC
Explanation: 

Detailed explanation-1: -During DNA replication, each of the two strands that make up the double helix serves as a template from which new strands are copied. The new strand will be complementary to the parental or “old” strand. Each new double strand consists of one parental strand and one new daughter strand.

Detailed explanation-2: -Replication relies on complementary base pairing, that is the principle explained by Chargaff’s rules: adenine (A) always bonds with thymine (T) and cytosine (C) always bonds with guanine (G).

Detailed explanation-3: -The initiation of DNA replication occurs in two steps. First, a so-called initiator protein unwinds a short stretch of the DNA double helix. Then, a protein known as helicase attaches to and breaks apart the hydrogen bonds between the bases on the DNA strands, thereby pulling apart the two strands.

Detailed explanation-4: -DNA base pair. Under normal circumstances, the nitrogen-containing bases adenine (A) and thymine (T) pair together, and cytosine (C) and guanine (G) pair together. The binding of these base pairs forms the structure of DNA .

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