Nucleotide Structure: Pentose sugar

Nucleotide Structure: Pentose sugar

Nucleotide Structure: Nitrogenous Bases

DNA Linkage

• Phosphate group/phosphodiester bond• Nucleotides contain one, two, or three

phosphate groups

*nucleoside *nucleotide

Nucleic Acid Polarity

*Top of molecule hasfree 5’-phosphate

group

This is the 5’ end

*Bottom has a free 3’hydroxyl group

This is the 3’ end

*Early 1950’s Rosalind Franklin

*1953 Watson and Crick

Structural analysis of DNA

Complementarity

DNA Structure:

Brief Review of DNA Replication:

Nearest Neighbor Analysis (Kornberg 1956):

In vitro DNA synthesis

•Template DNA

•DNA polymerase

•dNTPs*dTTP*dCTP *dGTP*dATP

•Allow DNA replication to take place

•Denature DNA

•Treat with micrococcal nuclease-

yields mononucleotides with 3’ terminal phosphates

A

C

G

T

T

C

ssDNA:

*

ssDNA treated with micrococcal nuclease:

A

C

G

T

T

C

*

Exercise:

List all possible dinucleotides (analysis of nearest 5’ neighbor)

Which must be present in equal frequencies if the DNA strands are:

Parallel ? Antiparallel?