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26 Cards in this Set

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DNA
(deoxryibosenucleic acid)
the molecule of heredity
-allows genetic information to be passed from one generation to the next
Genes
-discrete packets in heritable information
-comprised of DNA
-genes are located on specific areas of chromosomes=locus(loci)
-geners are directions for protein synthesis
Chromosome
structure made of DNA and protein(histones)
Uncondensed DNA
-long, thread-like structure
-DNA usually exists in this form in a cell nucleus
Condensed DNA
-form that DNA takes prior to cell division
-DNA wraps around histones, forming a nucleosome
-Nucleosomes are coiled by other proteins (like a slinky)
-those coils are wrapped around proteins scaffolding to form a supercoil
Frederick Griffith
1920s: while attempting to make a vaccine for bacterial pneumonia, discovered that genetic information could be transferred from one strain of bacteria to another (transformation)
Frederick Griffith's experiment
-used 2 strains of Streotococcus pneumoniae: R strain-harmless to mice; S strain-deadly to mice
-the heat killed S-strain was mixed with the R-strain(living) and injected into mice as a possible vaccine
-mice died, Griffith examined the mice
-Griffith found live S-strain bacteria, proving that the genetic material from dead S-strain becaterua moved into the live R-strain bacteria
Avery, MacLeod, & McCarty
1940s: discovered that the molecule that changed the S-strain to the R-strain was DNA
-concluded that genes were made of DNA
Hershey & Chase
1950s: proved that DNA, not protein, was the hereditary material
"Blender Experiment"
-Hersehy and Chase used:
radioactive S (sulfur)-found in protein, NOT in DNA
radioactive P (phosphorus)-found in DNA, NOT in protein
-traced where the radioactivity showed up using viruses(bacterophages) that attack bacteria and replicate inside them
-radioactivity showed up inside bacteria (DNA) & not on outside of bacteria (protein coating) when using radioactive P
*did experiment twie, once w/ S and once w/ P
Nucleotides
-consist of three parts:
1. phosphate group(PO4)
2. sugar group(deoxyribose)
3. nitrogen-containing base:
Adamine, Guanine-purines(double rings)
Thymine, Cytosine-pyrimidines(single rings)
Structure of DNA
-shaped like a twisted ladder:double helix
-"backbone" or sides of ladder are mad of alternating sugars & phosphates
-"rungs' made of complementary base pairs
A=T C=G - - '=': Hydrogen bonds
X-ray diffraction
An analytical technique used to identify crystalline solids by measuring the characteristic spaces between layers of atoms or molecules in a crystal
Replication
*prior to cell division, DNA must make an exact copy of itself so that each new cell receives the correct genetic info
*occurs in nucleus
*requires enzymes
DNA helicase
breaks apart the DNA helix
DNA polymerase
moves along a single strand of DNA matching (pairing) a free nucleotide to one on the exposed strand
- base pairing
- catalyzes covalent bonds of sugar and phosphate
DNA ligase
joins the small DNA segments together into one long strand
Replication bubble
the unwound portion of the two parental DNA strands, separated by DNA helicase, in DNA replication
Replication forks
the place where enzymes synthesize two new DNA strands that are complemtary to the two parental strands
Free nucleotides
nucleotides that have not been joined together to form a DNA or RNA strand
Thymine pair
T=T
are present when there has been damage by UV rays
How does a long, thread-like molecule of DNA condense into a chromosome?
-uncondensed DNA wraps around histones, forming a nucleosome
-nucleosomes are coiled by other proteins (like a slinky)
-those coils are wrapped around a protein scaffolding to form a supercoil
How did Hershey and Chase prove that DNA, not protein, was the hereditary material?
By doing the "Blender Experiment"
How are the component parts of DNA arranged to form a double helix?
-shaped like a twisted ladder
-"backbone" made of alternating sugars and phosphates
-"rungs" made of complementary base pairs
What are the steps of DNA replication?
1. DNA helicase breaks apart the H-bonds between A,T,C,G - forms replication bubble & 2 replication forks
2. DNA polymerase goest to replicatoin fork site, recognizes chemically nucleotide bases, and then apirs it up with a free nucleotide found floating in the nucleus; the polymerase helps build the "backbone" by bonding sugars to PO4; polymerase always moves to "free sugar" end
3. DNA ligase creates 2 long strands of DNA
*replication rate is 100-700 nucleotides at the same time
How is UV ray damage to DNA repaired in the cell?
enzyme removes "thymine pair" and replaces it by A=T; DNA ligase reattach to DNA strands