13.2 The Structure of DNA

What are the building blocks for DNA?

• carbohydrates

• nucleotides

• lipids

• proteins

Answer explanation

The building blocks for DNA are nucleotides. Nucleotides are the correct choice because they are the individual units that make up DNA.

A DNA nucleotide may be made up of a phosphate group, along with _____.

• deoxyribose sugar and uracil

• ribose sugar and adenine

• deoxyribose sugar and thymine

• ribose sugar and cytosine

Answer explanation

A DNA nucleotide is composed of a phosphate group and deoxyribose sugar, along with thymine. This combination forms the backbone of DNA.

The building block of nucleic acids are nucleotides.  Nucleotides are composed of a sugar, a phosphate group, and a _________________ base.

• oxygen

• hydrogen

• nitrogen

• carbon

Answer explanation

Nucleotides, the building blocks of nucleic acids, consist of a sugar, a phosphate group, and a nitrogen base. The correct choice is nitrogen.

The backbone of a DNA molecule is made from a ______________ and a _______________ group.

• lipid, carbon

• sugar, phosphate

• nitrogen, oxygen

• nitrogen, sulfur

Answer explanation

The backbone of a DNA molecule is made from a sugar and a phosphate group. These two components form the repeating structure of the DNA molecule.

What 2 components make up the sides of the DNA ladder?

• Sugar and adenine

• Deoxyribose and thymine

• Sugar and phosphate

• Cytosine and guanine

Answer explanation

The sides of the DNA ladder are made up of sugar and phosphate, as indicated by the correct answer choice.

The shape of the DNA molecule is a double __________________?

• "S"

• helix

• rope

• curve

Answer explanation

The shape of the DNA molecule is a double helix. The two strands of DNA twist around each other like a twisted ladder, forming a helical structure.

What are the four nitrogen bases?

• adenine, thymine, guanine, cytosine

• adenine, lysine, prolene, guanine

• arganine, cytosine, lysine, purine

• lysine, cytosine, lucine, guanine

Answer explanation

The four nitrogen bases in DNA are adenine, thymine, guanine, and cytosine. These bases pair up to form the double helix structure of DNA.

Nitrogenous bases are held together by:

• covalent bonds

• phosphodiester bonds

• ionic bonds

• hydrogen bonds

Answer explanation

Nitrogenous bases in DNA are held together by hydrogen bonds.

Which one of the following nucleotide pair bonds would be found in a DNA molecule?

• adenine-guanine

• guanine-cytosine

• adenine-cytosine

• cytosine-uracil

Answer explanation

The correct nucleotide pair bond found in a DNA molecule is guanine-cytosine. This bond is formed by hydrogen bonding between the nitrogenous bases.

Who said, "The amount of A = the amount of T, and the amount of G = the amount of C"?

• Chargaff

• Avery

• Griffith

• Franklin

Answer explanation

According to Chargaff's rule, the amount of A is equal to the amount of T, and the amount of G is equal to the amount of C. Therefore, the correct answer is Chargaff.