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-contains all the genetic info in an organism
-both stores and transmits the genetic information
Functions of DNA (3)
1. carry info. from one generation to the next
2. source of the info for protein synthesis
3. easily copied for the purpose of cellular replication & to pass to offspring
-infected mice w/ bacterial cells
-disease causing bacterial cells killed the mice
-dead disease causing bacterial cells did not kill the mice
-harmless bacterial cells did not kill the mice
-dead disease causing bacterial cells mixed w/ living harmless bacteria killed the mice
-used radioactive markers to determine that genetic info. was passed by DNA and not proteins
-5 carbon sugar in a ring (Deoxyribose)
-phosphate group (PO4)
-nitrogenous base - 4 possibilites
Watson & Crick used...
Rosalind Franklin's x-ray crystallography (in England),
Chargaff's Rule, and
Hydrogen bonding to...
create the double helix
-2 nucleotide polymers wound around eachother like a spiral staircase
-the nitrogenous bases fit on the inside (hydrophobic)
a long string of DNA that contains all the genes & many of the proteins associated w/ DNA
How does it all fit into a cell?
It must be tightly packed & well organized to fit in the nucleus (eukaryotes) and cell (prokaryotes)
1st level of packaging
-the DNA is tightly wrapped around proteins (HISTONES)
-the attraction is electrostatic the + charged histone & - charged DNA
-the histones & DNA form small beadlike structures (NUCLEOSOMES)
-1 nucleosome contains: 5 histones & DNA
When a cell divides...
each daughter cell receives a complete set of chromosomes
-each new cell has a complete set of the DNA code
Before a cell can divide, what must happen?
the DNA must be copied
so there are 2 sets ready to be distributed to the new cells
What is the function of enzymes?
lower the energy required to break the bonds
makes the process possible
-normally, strands would not separate b/c it is not favorable (in terms of energy)
adds complementary nucleotides creating the new DNA strands in a specific direction (5' - 3')
DNA Polymerase also proofreads the new strand to
make sure the complementary bases are in the right place
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