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Chapter 13: The Molecular Basis of Inheritance
 DNA replication:  Watson and Crick deduced that DNA is a double helix and
built a structural model
...
The nitrogenous bases project into the interior, where they hydrogen-bond
in specific pairs: A with T, G with C
...
1 DNA is the gentic material
The Search for the Genetic Material: Scientific Inquiry
 T
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Morgan’s group showed that genes exists as parts of chromosomes,
two chemical components – DNA and protein -  What which provides the genetic
material? 
Evidence that DNA can
transform Bacteria
 Fredrick Griffith, a
british medical officer, in 1928
was trying to develop a vaccine
against pneumonia
...

One Pathogenic (disease-causing)
and one nonpathogenic
...


 used a radioactive isotope of sulfur to tag protein in one batch of T2 and a
radioactive isotope of phosphorus to tag DNA in a second patch
...
– the atoms of radioactive phosphorus labeled
only the DNA  The researchers then tested the two samples shortly after
the onset of infection to see which type of molecule –protein or DNA – had
eneter the bacterial cells 
 Hershey and Chase concluded that the DNA injected by the phage
must be the molecule carrying the genetic information that makes the cell
produce new viral DNA and proteins
...

Building a Structural Model of DNA: Scientific Inquiry
 Watson and Crick deduced that DNA is a double helix and built a structural
model
...

The nitrogenous bases project into the interior, where they hydrogen-bond in specific pairs:
A with T, G with C
...
2 Many proteins work together in DNA replication and repair
 The Mesolson-Stahl Experiment showed that DNA Replication is
semiconservative: The parntal molecule unqinds, and each strand then serves as a
template for the synthesis of a new strand according to base-pairing rules  DNA
Replication at one replication fork is summarized here:

 DNA Polymerases proofread new DNA, replacing incorrect necleotides
...
Nucleotide excision repair
is a general process by which nucleases cut out and replace damaged straches of
DNA
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3 A chromosome consists of a DNA molecule packed together with proteins
 The chomosome of most bacterial species is a circular DNA molecule with some
associated proteins, making up the nucleoid of the cell
...
Additonal
coiling and folding lead ultimately to the highly condensed chromatin of the metaphase
chromosome
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Euchromatin, but not
heterochromatin, is generally accessible for transcription of genes
...
4 Understanding DNA structure and replication makes genetic engineering
possible
 Gene cloning (or DNA cloning) produces multiple copies of a gene (or DNA
fragment) that can be used to manipulate and
analyze DNA and to produce useful new
products or organisms with benefical traits 
 In genetic engineering, bacterial
restriction enzymes are used to cut DNA
molecules within short, specific nucleotide
sequences (restriction sites), yielding a set of
double-stranded restriction fragments with
single-stranded sticky ends 
 DNA fragments of different lengths
can be separated and their lengths assessed by
gel electrophoresis 
 The sticky ends on restriction
fregments from one DNA source – such as
bacterial plasmid or other cloning vectorb –
can base-pair with complimentary sticky ends
on fragments from other DNA molecules;
sealing the base-paired fragments with DNA
ligase produces recombiant DNAB molecules
...
PCR uses
primers that bracket the desired segment and
requires a heat-resistant DNA polymerase
...




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