Question

1. what components make up a nucleotide in dna?

a. phosphate group, lipid molecule, and nitrogenous base
b. sugar molecule, phosphate group, and nitrogenous base
c. sugar molecule, nitrogenous base, and lipid group
d. sugar molecule, phosphate group, and oxygen atom

1. what is the complementary strand for the dna sequence atg - gta?

a. tag - cat
b. atg - cat
c. agc - att
d. tta - gca

1. which of the following correctly describes the structure of dna?

a. triple - stranded helix
b. double - stranded helix
c. single - stranded helix
d. coiled structure without nucleotides

Explanation:

Question 7

A nucleotide in DNA consists of a deoxyribose sugar (sugar molecule), a phosphate group, and a nitrogenous base (adenine, thymine, cytosine, or guanine). Lipids are not part of a nucleotide, so options a and c are incorrect. Option d includes an oxygen atom which is not a main component of a nucleotide's structure. Option b has the correct components: sugar molecule, phosphate group, and nitrogenous base.

In DNA base pairing, adenine (A) pairs with thymine (T), and cytosine (C) pairs with guanine (G). For the sequence ATC - GTA, we replace each base with its complement: A→T, T→A, C→G, G→C, T→A, A→T. So ATC becomes TAG and GTA becomes CAT. Thus the complementary strand is TAG - CAT.

The structure of DNA is a double - stranded helix. It is composed of two strands of nucleotides that wind around each other. It is not triple - stranded (option a is wrong), not single - stranded (option c is wrong), and it is made up of nucleotides (so option d is wrong).

Answer:

b. Sugar molecule, phosphate group, and nitrogenous base

Question 8