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BIOL 111 CHAPTER 16
the molecular basis of inheritance
42
Biology
Undergraduate 1
11/05/2009

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Term
who introduced the double hilical model for dna?
Definition
james watson an dfrancis crick in 1953
Term
who discovered that genes were located on chromosomes?
Definition
t.h. morgan
Term
who discovered teh genetic role of dna? what did he study?
Definition
frederick griffith in 1928.  he worked with two strains of bacterium, one pathogenic and one harmless
Term
what happened when griffith mixed the heat killed reamins of a pathogenic strain with the living cells of a harmless one? what did he call this phenomenon?
Definition
some of the living became pathogenic.  he called it tranformation, a change in genotype and phenotype due to assimilation of foreign dna
Term
who discovered what the transforming substance was in griffith's experiment.  why were many biologists skeptical about this discovery?
Definition
Oswald Aver, Maclyn Mccarty and Colin MacLeod.  little was known about dna at the time
Term
bacteriophages
Definition
or simply phages are viruses that infect bacteria
Term
who showed that dna is the genetic matierial of a phage known as T2?
Definition
alfred hershey and martha chase
Term
who reported that dna composition varies from one species to teh next? what did this do for dna as a genetic material?
Definition
erwin chargaff in 1950.  it made dna a more credible candidate for genetic material.
Term
chargaff's rule
Definition
in any species there is an equal number of A and T bases, and an equal number of G and C bases
Term
who studied teh molecular structure of dna with x ray crystallogrophy?
Definition
maurice wilkins and roalind franklin
Term
double helix
Definition
two strands of dna coiling making a two spirals
Term
who concluded that there were two antiparallel sugar-phosphate backbones with nitrogenous bases paired in teh molecule's interior?
Definition
Franklin
Term
what is watson and crick's semiconservative model?
Definition
when a doubel helix replicates, each daughter molecule will have one old strand derived or conserved from teh parent molecule and one newly made strand
Term
whose experiments suppored teh semiconservative model?
Definition
matthew meselson and franklin stahl's
Term
origins of replication
Definition
site where replication begins.  the two dna strands seperate opening up a replication bubble
Term
explain replication role of the replication bubble in eukaryotic chromosome replication.
Definition
hundreds or even thousands of bubbles form and seperate the strand in both directions from each origin until entire molecule is copied
Term
replication fork
Definition
the ends of replication bubbles, a y shaped region where new dna strands are elongating
Term
helicases
Definition
enzymes that untwist the double helix at the replication forks
Term
single strand binding protein
Definition
this protein binds to and stablizes single stranded dna until it can be used as a template
Term
topoisomerase
Definition
corrects overwinding ahead of replication forks by breaking, swiveling, and rejoining dna strands
Term
primer
Definition
a short stretch of rna with a free 3' end, bound by complementary base pairing to the template strand, that is elongated with dna nucleotides during dna replication
Term
primase
Definition
enzyme that joins rna nucleotieds to make the primer using the parental dna strand as a template
Term
dna polymerases
Definition
catalyze teh elongation of new dna at the replication fork
Term
leading strand
Definition
the new complementary dna strand synthesized consinuously along the template strand toward the replication fork in the mandatory 5' --> 3' direction
Term
lagging strand
Definition
a discontinuously synthesized dna strand that elongates by means of okazaki fragments, each synthesized in a 5' --> 3' direction away from the replication fork
Term
okazaki fragments
Definition
a short segment of dna synthesized away from the replication fork on a template strand during dna replication, many of which are joind together to make up the lagging strand of newly synthesized dna
Term
dna ligase
Definition
a linking enzyme essential for dna replication; catalyzes the covalent bonding of the 3' end of one dna fragment (such as an okazaki fragment) to the 5' end of another dna fragment ( such as a growing dna chain)
Term
mismatch repair
Definition
repair enzymes correct erros in base pairing
Term
nucleotide excision repair
Definition
a nuclease cuts out and replaces damaged stretechs of dna.  it cuts in such a way that it can immortalize mutations
Term
telomeres
Definition
the tandemly repetitive dna at the end of a eukaryotic chromosome's dna molecule that protects the organism's genes from being eroded during successive rounds of replication.  TTAGGG
Term
telomerase
Definition
catalyzes the lengthening of telomeres in germ cells
Term
transformation
Definition
change in genotype or phenotype due to assimilation of foreign dna
Term
what's requires more energy to break, adenine and thymine or guanine and cytosine and why?
Definition
guanine and cytosine requires more energy to break because they have more hydrogen bonds
Term
nucleoid
Definition
region in bacteria where is found dna in a supercoild state
Term
chromatin
Definition
complex of dna and protein found in the nucleus of eukaryotic cells
Term
histones
Definition
proteins that are responsible for packagine teh first level of dna in chromatin
Term
nucleosome
Definition
beads formed when dna winds around histones.  nucleosomes are strung together like beads on a string by lnker dna.  10 - nm fiber
Term
30 nm fiber
Definition
interactions between nucleosomes cause the thin fiber to coil or fold into this thicker fiber
Term
300 nm fiber
Definition
the 30 nm fiber forms looped domains that attach to proteins
Term
metaphase chromosome
Definition
the loops domains that further coil.  the width of a chromatid is 700 nm
Term
euchromatin
Definition
loosely packed chromatin
Term
heterochromatin
Definition
highly condensed chromatin
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