9.4

3. Give the one-letter abbreviation for each type of nitrogen-containing base classified as a purine. Separate your responses by one space.

A G

2. Use the terms listed below to correctly explain concepts, assigned figures, and specified end-of-chapter questions Phosphodiester linkage Backbone Directionality 5' to 3'

Phosphate groups at the 5' C of sugar forms ester bonds with the 3'OH of the next nucleotide forming phosphodiester linkage. Because of the phosphate negative charge, the backbone has a negative charge. Bases are pointing inward from the backbone. The directionality of a nucleotide is from 5' to 3' from Phospate C 5' to OH 3' . So the directionality is a 5' to 3'

directionality

Refers to the 5' to 3' orientation of the sugars in the polynucleotide strands.

backbone

Refers to the alternating sugar and phosphate groups along the "rail" of the polynucleotide strand.

1. In a DNA strand, a phosphate connects a 3ʹ carbon atom in one deoxyribose to a. a 5ʹ carbon in an adjacent deoxyribose. b. a 3ʹ carbon in an adjacent deoxyribose. c. a base in an adjacent nucleotide. d. none of the above.

a

2. What is meant by the phrase "directionality" with regards to DNA and RNA?

all sugar molecules have the same orientation. In this example, the direction of the strand is 5ʹ to 3ʹ when going from top to bottom. Both DNA and RNA in 5' to 3' direction !

8. The sequence of ______ (one word) within the DNA and RNA is the defining feature that allows nucleic acids to carry information

bases

2. If a 2'-H is observed in the sugar of a nucleotide, then you know the sugar is:

deoxyribose

7. The phrase "5' to 3'" or "3' to 5'" is used to indicate ____________ (one word).

directionality

5, What two-word phrase is used to describe the structure resulting from the interactions between the two polynucleotide strands of DNA?

double helix

1. Describe the structural features of a DNA strand.

A phosphate group connects two sugar molecules via ester bonds. For this reason, the linkage in DNA or RNA strands is called a phosphodiester linkage. The phosphates and sugar molecules form the backbone of a DNA or RNA strand. The bases project from the backbone. The backbone is negatively charged due to a negative charge on each phosphate. A second important structural feature is the orientation of the nucleotides. As mentioned, the carbon atoms in a sugar molecule are numbered in a particular way. In Figure 9.10, the 5ʹ carbons in every sugar molecule are above the 3ʹ carbons. Therefore, a strand has a directionality because all sugar molecules have the same orientation. In this example, the direction of the strand is 5ʹ to 3ʹ when going from top to bottom.

phosphodiester linkage

A phosphate group connects two sugar molecules via ester bonds. For this reason, the linkage in DNA or RNA strands is called a.. Type of bond that holds adjacent nucleotides together and is formed via a dehydration synthesis reaction.

C4. What are the building blocks of a nucleotide? With regard to the 5ʹ and 3ʹ positions on a sugar molecule, how are nucleotides linked together to form a strand of DNA?

Answer: The building blocks of a nucleotide are a sugar (ribose or deoxyribose), a nitrogenous base, and a phosphate group. In a nucleotide, the phosphate is already linked to the 5 position on the sugar. When two nucleotides are hooked together, a phosphate on one nucleotide forms a covalent bond with the 3 hyrdroxyl group on another nucleotide.

5' to 3'

Therefore, a strand has a directionality because all sugar molecules have the same orientation. In this example, the direction of the strand is 5ʹ to 3ʹ when going from top to bottom. fig 9.10

4. Give the one-letter abbreviation of the pyrimidine base found only in RNA

U

1. What is the repeating structural unit of nucleic acids?

nucleotides

1. What two functional groups participate in formation of the phosphodiester linkage between adjacent nucleotides on a polynucleotide strand?

phosphate groups between two sugars via ester bonds

6. What specific type of linkage is formed between adjacent nucleotides by removal of water? (One word

phosphodiester