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CHAPTER 16 - Coggle Diagram
CHAPTER 16
THE MOLECULAR BASIS OF INHERITANCE
virus
a DNA enclosed by a protein
bacteriophage
virus that affects bacteria
DNA
A polymer of nucleotides each consisting of a nitrogen base, a sugar and a phosphate group.
pyrimidine
C and T
purine
A and G
DNA replication
copying of DNA
begins at origins of replication
where the two DNA strands are separated opening up a replication bubble
replication york
a Y shaped region where parental DNA strands are being unwound
helicases
enzymes that untwist the double helix at the replications forks
single strand binding proteins bind to and stabilize single stranded DNA
topoisomerase
relieves the strain of twisting of the double helix by breaking and rejoining DNA strands
dna can be damaged by exposure to harmful chemical or physical agents like cigarette
mismatch repair of dna
repair enzymes replace incorrectly paired nucleotides that have evaded the proofreading process
nucleotide excision repair
a nuclease cuts out and replaces damaged stretches of dna
telomeres
special nucleotide sequences at dna ends
dna is precisely combined with proteins in a complex called chromatin
histones
are responsible for the main level of dna packing in interphase chromotin
nucleosome
composed of dna wound twice around a core of eight histones two each of the four main histone types
euchromatin
loosely packed chromatin
synthesizing a new DNA strand
a primer
allows DNA polymerase to synthesize new DNA strands
synthesized by the enzyme primase
DNA polymerase
catalyze the synthesis of new dna at the replication fork
they require a primer
synthesis a leading strand moving toward the replication fork
the lagging strand is synthesized as a series of segments called okazaki fragments
joined together by DNA ligase
semiconservative model
predicts that when a double helix replicates , each daughter molecule will have one old strand and one newly made starnd
two components of chromosomes
dna
proteins
chargaff's rule
the base composition of dna vries between species
the number of T and A in any species is equal and G and C are equal
how dna structure accounts for its role
maurice Wilkins and Rosalind Franklin used a technique called X-ray crystallgraphy
Franklin's X-ray allowed James Watson to deduce that DNA was helical
Frankin's X-ray images suggested that the DNA molecule was made up of two strands forming a double helix
Watson built a model in which the backbones were antiparallel
that pairing a purine A or G with a pyrimidine C or t resulted in a uniform width consistent with X -ray data
determined that A paired with T only, and G with C only