THE MOLECULAR BASIS OF INHERITANCE
DNA REPLICATION
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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The phosphate of the new nucleotide attaches to the 3’C of the previous nucleotide
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The phosphate of the new nucleotide attaches to the 5’C of the previous nucleotide
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The 3’C of the new nucleotide attaches to the phosphate of the previous nucleotide
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The 5’C of the new nucleotide attaches to the phosphate of the previous nucleotide
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Detailed explanation-1: -DNA is always synthesized in the 5’-to-3’ direction, meaning that nucleotides are added only to the 3’ end of the growing strand. As shown in Figure 2, the 5’-phosphate group of the new nucleotide binds to the 3’-OH group of the last nucleotide of the growing strand.
Detailed explanation-2: -One of the key molecules in DNA replication is the enzyme DNA polymerase. DNA polymerases are responsible for synthesizing DNA: they add nucleotides one by one to the growing DNA chain, incorporating only those that are complementary to the template.
Detailed explanation-3: -The DNA is only copied in the 5’ to 3’ direction because eukaryotic chromosomes have many origins for each chromosome in keeping with their much larger size. If some were copied in the other direction, mistakes will happen. It keeps every cell division on the same page, so to speak.
Detailed explanation-4: -The nucleotide exists in the triphosphate form before being added to the chain, and the removal of two of the phosphate groups provides the energy to bind it to the growing chain. This is why nucleotides are only added on the 3’ end.
Detailed explanation-5: -Nucleotides are formed from nucleosides by the esterification of inorganic phosphate to the C5 on the aldose. Specific nucleotides, namely nicotinamide dinucleotide (NAD+), 7 flavin adenine dinucleotide (FAD) and the adenosine phosphates, are essential to energy generation, storage and transfer (Section 5.1).