When DNA replication begins, which of the following happens?

The bond between the nitrogen base and sugar of each nucleotide breaks.

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The hydrogen bonds between the nucleotides forming a base pair break.

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The phosphodiester bonds between adjacent nucleotides break.

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DNA ligase unzips the double helix.

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Solution

The correct option is B The hydrogen bonds between the nucleotides forming a base pair break.
At points where DNA synthesis has been initiated, the enzyme helicase (more specifically DNA helicase) uses energy to help unzip the double helix of the parental DNA by breaking the hydrogen bonds between the nucleotides of each base pair. It thus, forms the replication fork so that each of the two parental DNA strands (known as templates) could be copied from.

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Similar questions

Q. Find the hydrolysis product when a phosphodiester bond of nucleotide breaks.

Match the following enzymes of DNA replication with their respective functions:
$\begin{matrix} p . D N A p o l y m e r a s e & i . H e l p s u n z i p t h e D N A d o u b l e h e l i x q . D N A l i g a s e & i i . S e a l s n i c k s b e t w e e n O k a z a k i f r a g m e n t s r . D N A h e l i c a s e & i i i . L a y s R N A p r i m e r s t o w h i c h p o l y m e r a s e c a n a d d n u c l e o t i d e s s . P r i m a s e & i v . A d d s n u c l e o t i d e s t o t h e f r e e 3^{'} e n d o f R N A p r i m e r s \end{matrix}$

Q. Which of the following are correctly matched?
1. Ligase - Joins short segments of DNA together
2. DNA polymerase - cuts DNA at specific site
3. Helicase breaks hydrogen bond between complementary pairs during DNA replication

Q. Assertion :The sugar phosphate backbone of two chains in DNA double helix show anti-parallel polarity. Reason: The phosphodiester bonds in one strand go from a 3 carbon of one nucleotide to a 5 carbon of adjacent nucleotide, whereas those in complementary strand go vice versa.

Q. Identify the pair of nucleotides which is joined by three hydrogen bonds in double-stranded DNA

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