Nucleotides and DNA Replication Mechanisms

Nucleoside

Nitrogenous base linked to a pentose sugar.

Nucleotide

Nucleoside with a phosphate group included.

Purines

Adenine and guanine; two-ringed structures.

Pyrimidines

Cytosine, thymine, uracil; single-ring structures.

Thymine

Pyrimidine in DNA with a methyl group.

Uracil

Pyrimidine in RNA without a methyl group.

NTP

Nucleoside triphosphate; building blocks of RNA.

dNTP

Deoxynucleotide triphosphate; building blocks of DNA.

1' Position

Carbon attached to the nitrogenous base.

2' Position

Carbon attached to H (deoxyribose) or OH (ribose).

3' Position

Carbon with hydroxyl group at DNA's end.

5' Position

Carbon with phosphate group outside the ring.

5' to 3' Directionality

DNA polymerase moves from 5' to 3' end.

Chargaff's Rule

A=T and G=C ratios in DNA.

Franklin's Discovery

DNA exists in a double helix structure.

Watson & Crick

First accurate depiction of DNA structure.

Semi-Conservative Replication

Produces two copies with one original strand.

Meselson and Stahl

Experiment supporting semi-conservative DNA replication.

RNA Polymerase

Synthesizes RNA from DNA template during transcription.

Origin of Replication

Site where DNA replication begins.

Replication Forks

Areas where DNA strands are unzipped.

Primase

Enzyme synthesizing RNA primers on DNA strands.

DNA Polymerases

Enzymes that assemble nucleotides into DNA.

DNA Ligase

Catalyzes bonding of DNA fragments' ends.

Helicase

Unwinds DNA to move replication forks forward.

Single-Strand Binding Proteins

Protect single-stranded DNA from degradation.

Topoisomerase

Relieves tension from unwinding DNA double helix.

Telomerase

Extends telomeres using RNA template for synthesis.

Telomeres

Compound structures at chromosome ends.