AP BIOLOGY

THE MOLECULAR BASIS OF INHERITANCE

DNA REPLICATION

Question [CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
How does DNA replicate?
A
The deoxyribose of a free nucleotide is linked to the phosphate of the last nucleotide in the chain.
B
The phosphate of a free nucleotide is linked to the deoxyribose of the last nucleotide in the chain.
C
Nucleotides are linked in a 3’ to 5’ direction and the new strands are anti-parallel to the template strands.
D
Nucleotides are linked in a 5’ to 3’ direction and the new strands are parallel to the template strands.
Explanation: 

Detailed explanation-1: -The phosphate of a free nucleotide is linked to the deoxyribose of the last nucleotide in the chain. Nucleotides are linked in a 3′ to 5′ direction and the new strands are anti-parallel to the template strands. Nucleotides are linked in a 5′ to 3′ direction and the new strands are parallel to the template strands.

Detailed explanation-2: -The phosphate groups of nucleotides are joined to the 5′ hydroxyl group of the sugar component in an ester or anhydride linkage. Several forms of nucleoside phosphate compounds are possible, containing up to three esterified phosphate groups polymerized off the ribose or deoxyribose unit.

Detailed explanation-3: -A DNA molecule consists of two long polynucleotide chains composed of four types of nucleotide subunits. Each of these chains is known as a DNA chain, or a DNA strand. Hydrogen bonds between the base portions of the nucleotides hold the two chains together (Figure 4-3).

Detailed explanation-4: -When nucleotides are incorporated into DNA, adjacent nucleotides are linked by a phosphodiester bond: a covalent bond is formed between the 5’ phosphate group of one nucleotide and the 3’-OH group of another (see below). In this manner, each strand of DNA has a “backbone” of phosphate-sugar-phosphate-sugar-phosphate.

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