Two strands of DNA - are held together by

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Q: 117 (CDS-I/2014)
Two strands of DNA - are held together by

question_subject: 

Science

question_exam: 

CDS-I

stats: 

0,33,37,33,20,6,11

keywords: 

{'dna': [3, 1, 1, 2], 'hydrogen bonds': [0, 0, 0, 1], 'covalent bonds': [0, 0, 0, 2], 'strands': [0, 0, 1, 2], 'electrostatic force': [0, 0, 0, 1], 'forces': [0, 0, 0, 1], 'van der waals': [0, 0, 0, 1]}

The correct answer is option 1, hydrogen bonds.

DNA, which stands for deoxyribonucleic acid, is a double-stranded molecule consisting of two strands. These two strands are held together by hydrogen bonds. Hydrogen bonds form between specific nucleotide bases on each strand. In DNA, there are four types of nucleotide bases: adenine (A), thymine (T), cytosine (C), and guanine (G). Adenine always pairs with thymine, and cytosine always pairs with guanine.

Hydrogen bonds form when a hydrogen atom from one nucleotide base forms a weak bond with an electronegative atom, such as oxygen or nitrogen, from the complementary nucleotide base on the other strand. These hydrogen bonds are relatively weak compared to covalent bonds, which are much stronger. However, the collective strength of multiple hydrogen bonds along the length of the DNA molecule helps to keep the two strands tightly bound together.

It is important to note that the other options - covalent bonds, electrostatic forces, and van der Waals` forces - are not involved in holding the two strands of DNA together.