DNA Structure and Genome Organization (unfinished slide 15)

What are prokaryotic and eukaryotic genomes made out of?

Double-stranded DNA

What are viral genomes made out of?

DNA or RNA that are single stranded or double-stranded

What is a polymer?

A chain of repeating units

What is a nucleotide?

a single unit in a polymer

What are nucleotides made out of?

• a ribose sugar

• a nitrogenous base

• a phosphate group

Which sugar is in DNA? Ribose or Deoxyribose

Why?

Deoxyribose

• Makes DNA more stable

• Because it does not form hydrolysis bonds

• Better for long-term storage

Which sugar is in RNA? Ribose or Deoxyribose

Why?

Ribose

• Has a hydroxyl group that is reactive at the 2^’ carbon

• Less stable

• Used for temporary tasks

Describe pyrimidine

Name the structures

• A nitrogenous base that is double-ringed

• Larger molecules with 4 nitrogens

Structures:

• Adenine (A)

• Guanine(G)

Describe pyrimidine

Name the structures

• A nitrogenous base that is a single 6-membered ring

• 2 nitrogens

Structures:

• Cytosine (C)

• Thymine (T) — DNA only

• Uracil (U) —RNA only

Are nucleic acids hydrophilic or hydrophobic?

Why?

Hydrophilic because of the negatively charged phosphate groups

What did Rosalind Franklin figure out about DNA

• 2 nm wide and 0.34nm from adjacent base pairs

• 3.4 for a complete turn

• It was a regular, repeating helical structure

Describe double helix DNA

• 2 strands of nucleotides run antiparallel

• sugars and phosphate are on the outside, and the nitrogenous bases are on the inside

• winds clockwise to make a right-handed helix

• the helix is 20 A wide

• base pairing by hydrogen bonds

• 2 strands are complementary, not identical

What is the primary structure of DNA?

The nucleotide sequence (bases)

What is the secondary structure of DNA?

The double helix

What is the tertiary structure of DNA?

The higher level organization of the double helix