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DNA is the molecular basis of heredity, exploring the structure of DNA and how it replicates
bacterial viruses, structure consists of of DNA and protein, DNA containing head, tail and tail fibers that attach to surfaces susceptible to bacteria.
Hershey and Chase experiment
knew that phages held genetic information, made only of only proteins (20 different monomers) and DNA (4 monomers) one goes into the host cell, 1. they mixed radioactively labelled phages with bacteria, the phages infect bacteria, they wanted to track where the DNA went and where the Protein goes. Put it in centrifuge and tested for radioactivity. the protein caused radioactivity outside the cell, DNA radioactivity was found inside the pellet. discovered DNA was the genetic info of phages.
polymer built of nucleic acids, example is the structure of DNA with the arrangement of the nucleotides A, T, C, and G
the nucleotides are joined to one another by covalent bonds between the sugar of one nucleotide and the phosphate of the next, ________________ a repeating pattern of sugar-phosphate, nitrogenous bases are arranged along this backbone
four nucleotides found in DNA
Thymine (T), Cytosine (C), Adenine (A), guanine (G),
T and C are single ringed structures, A and G are double ring structures
Watson and Crick experiment
used copy of Photo 51, and knowledge to gather that 1. DNA is a double helix, 2. helix diameter is uniform, 3. Phosphate on outside of helix is negatively charged.
A=T, C=G relative proportions of basis of DNA in every species, later changed to Base pair rule
X ray crystalography, found structure of a model of DNA, photo 51, didn't share it.
Found by Franklin, Wilkins stole Photo 51, copied it on newspaper with W and C, returned photo and Franklin never knew, shows X which means double helix, horizontal line through X (at the angel it is rotated) tells how tight the helix is.
the orietnation of DNA strands, running in opposite directions, copmliment, 3 prime to 5 prime then opposite would run 5 prime to 3 prime
number of carbons
______________ __ ________ only go from 5 prime to 3 prime and 3 prime to 5 prime, one direction
The three theories of DNA replication
1. conservative model: whole DNA molecule would be consumed 1rst gen: 1 exact parent replication and 1 new, 2nd gen: 1 original 3 new
2. semiconservative: produces DNA molecules 1 strand old and 1 strand new.
3. Disperative model: each strand of both daughter molecules contain a mixture of old and newly synthesized parts
density experiment to find the way DNA replicates, Nitrogen 15( number of neutrons, does not change property of atom, all DNA made of nitrogen, then bacteria grows and divides)they tracked old heavy DNA, with new lighter DNA, used a centrifuge and gel electrophysis to separate molecules on size- grows and divide in 20 minutes, just once, centrifuged it then found medium Density DNA so no to the conservative method, found that DNA replicates semi-conservatively.
split the two strands of DNA, 2 strands separate and separate the two nucleotide strips that are complementary to each other (a and T, c and G)
DNA polymerase on leading strand
travels down reading each of the sequences on the parental strips and putting the complementary nucleotide on the leading strand, DNA polymerase build 5 to 3, leading strands run in opposite direction 3 to 5 so it works
DNA polymerase on lagging strand
cannot build because both are going from 5 to 3 so needs to build in fragments, builds away from the replication fork, goes in opposite direction.
enzyme that can start from scratch to build DNA primer, which allows DNA polymerase to add nucleotides
built in pieces, RNA clamp attaches to DNA polymerase, joined together removes RNA replaces DNA
heating and cooling
______________ DNA breaks the bonds like helicase and __________ puts DNA back together like DNA ligase
makes it easy to determine exactly what genes are active in particular cells at particular times
a method for physically sorting macromolecules proteins or nucleic acids- primarily on the basis of their electrical charge and size
extract DNA from some of cells and treat it with a restriction enzyme, mixture of DNA pieces, the number of these and their sizes reflect the specific sequence of nucleotides in your DNA
"jumping genes", a segment of DNA that can move from one site to another within a cell and serve as an agent of genetic change
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