Honors Biology DNA Replication

DNA Replication

process by which DNA molecule is copied; DNA synthesis (S stage of interphase)

Transformation

a change in genotype and phenotype due to the assimilation of external DNA by bacteria

Bacteriophages

Viruses that infect bacteria

Bacteria eaters

Virus

infects a cell and takes over the cell's metabolic machinery

Chargaff's Law

the base compostion of DNA varies between species and for each species, the percentages of A and T bases are roughly equal to the percentages of the G and C bases

Rosalind Franklin

X-ray crystallographer that discovered the double helix of DNA

Watson and Crick

discovered the structural double helix model of DNA

Double helix

two twisted strands

Antiparallel

subunits run in opposite directions

Nitrogenous bases of Dna

A, T, C, G

Purines

A and G

Nitrogenous bases with two organic rings

Pyrimidines

C and T

Nitrogenous base with a single organic ring

Semiconservative Model

the two strands of the parental molecule separate and each functions as a template for synthesis of a new complementary strand- most common

Origins of Replication

short stretches of DNA having a specific sequence of nucleotides

Replication Fork

a Y shaped region where the parental strands of DNA are being unwound

Helicases

enzymes that untwist the double helix at the replication forks, separating the two parental strands and make them available as template strands

Leading strand

Strand that continuously adds nucleotides to the new complementary strand as the fork progresses

Lagging Strand

The strand that DNA polymerase works away from the replication fork; Synthesized discontinuosly as a series of segments

Okazaki fragments

Series of segments that are 1000-2000 nucleotides long

DNA Ligase

joins the sugar phosphate backbones of all the Okazaki fragments into a continuous DNA strand

DNA polymerase

Synthesizes new DNA strands by adding nucleotides to a pre-existing DNA strand

Mismatch repair

Other enzymes remove and replace incorrectly paired nucleotides that have resulted from replication errors

Histones

Proteins that are responsible for the first level of DNA packing in chromatin

Chromatin

complex of DNA and protein

Nucleotide

A building block of DNA, consisting of a five-carbon sugar covalently bonded to a nitrogenous base and a phosphate group.

template strand

DNA strand that provides the pattern for ordering, by complementary base pairing, the sequence of nucleotides

complementary nucleotides

A-T

G-C

DNA directionality

one end has an exposed hydroxl group on the 3' carbon of deoxiribose and the other end has an exposed phosphate group on a 5' carbon

DNA structure

consists of two long chains of nucleotides twisted into a double helix and joined by hydrogen bonds between the complementary bases adenine and thymine or cytosine and guanine

antiparallel strands

Strands parallel to each other going in opposite directions (3'-5' and 5'-3')

Purine bases

have a double ring structure and include adenine and guanine.

Pyrimidine bases

Single ring structure; Cytosine, Thymine, Uracil