DNA structure can be described as a twisted ladder. Imagine you are climbing a model of DNA, just as if you were climbing a ladder. What parts of a nucleotide are your feet touching as you climb?

The parts of a nucleotide that touch the feet when climbing are the four nitrogenous bases, namely: adenine, thymine, guanine and cytosine

Explanation:

The "handrails" of the DNA ladder are made of sugar phosphate, which protects the information in which the "steps" are transported. Each unit of sugar phosphate is attached to the next with a covalent bond.

Among the "handrails" of the DNA ladder are weaker hydrogen bonds that connect the two halves of the "steps." The "steps" of the DNA ladder are made of the nitrogenous bases: adenine, thymine, guanine and cytosine. Among them they form complementary pairs, for example, adenine binds with thymine, and guanine with cytosine.

The Nitrogenous Bases

Explanation:

DNA is a double helical structure, comprising nitrogenous bases, phosphate groups and deoxyribose sugars. A phosphate group is attached to a nitrogenous base and a deoxyribose sugar to form a nucleotide.

There are four types of nitrogenous bases in the DNA sequence. These are:

The deoxyribose sugar ensures the structural integrity of a nucleotide however, DNA is arranged such that the nitrogenous base of one nucleotide, is attached to the nitrogenous base of another nucleotide, pairing in a pattern known as complementary base pairing.

Adenine pairs with Thymine and Cytosine pairs with Guanine. This pairing, gives the continuous ladder appearance to DNA strands.

i guess the correct option is letter a.

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