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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
