Chapter 12 DNA 121 Identifying the Substance of Genes 122 The Structure of DNA 123 DNA Replication 121 Identifying the Substance in Genes Genes A section of DNA on a chromosome in a nucleus ID: 934081
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Slide1
Chapter 12: DNA
Lab Biology CP
Slide2Chapter 12: DNA
12.1 Identifying the Substance of Genes12.2 The Structure of DNA12.3 DNA Replication
Slide312.1 Identifying the Substance
in Genes
Slide4Genes
A section of DNA on a chromosome in a nucleusEach chromosome contains hundreds of genescontains most of your characteristics: hair color, skin color, how things taste to you, etc.
Contains the instructions for making a specific protein
Determines the order of amino acids in making proteins
Slide5Slide6Bacterial TransformationFrederick Griffith’s Experiment
Injected mice with 4 different samples of bacteriaHeat-killed diseasing causing bacteria injected mice LIVED
Live, harmless bacteria injected mice LIVED
The 2 strains together caused fatal pneumonia
Concluded:
genetic info could be transferred from one bacterial strain to another
Transformation
: when one type of bacteria (harmless) changed
permanently
into another (disease causing form)
The transforming factor must be a
GENE!!!
http://www.youtube.com/watch?v=eovTbQgan5M
Slide7Griffith’s Experiment
Slide8Oswald Avery’s Experiment
By observing bacterial transformation, he discovered that DNA stores and transmits genetic information from one generation to the next.DNA is responsible for transformation
Slide9Avery’s Experiment
Slide10Bacterial Viruses
Bacteriophage: a virus that infects bacteriahttp://www.youtube.com/watch?v=41aqxcxsX2w&feature=related
Slide11The Hershey-Chase Experiment
Studied a bacteriophage composed of a DNA core and a protein coatThey wanted to determine what part entered the bacterial cell (the DNA or protein coat)
Used radioactive markers to label the DNA and proteins
Results: The
bacteriophages
only injected
DNA
, not proteins, into the bacterial cells
Slide12Slide13Slide14The Role of DNA
The DNA that makes up genes must be capable of:1.)
storing
,
2.)
copying
,
3.)
transmitting
, and t
he genetic information in a cell
Slide1512.2 The Structure of DNA
Slide16DNA
Deoxyribonucleic
A
cid
Slide17Structure of DNA
Double-stranded
Double-helix
Side ladders
:
Sugar (
deoxyribose
) and phosphate group
Held together by hydrogen bonds
Steps of ladder:
4 nitrogen
bases (nucleotides)A-T (
adenine and thymine
)
C-G (
cytosine and guanine
)
http://www.youtube.com/watch?v=qy8dk5iS1f0
Slide18DNA Scientists
Erwin Chargaff’s RuleBase pairing
A-T and C-G
http://www.youtube.com/watch?v=VIlF6fovLZE&feature=related
Rosalind
Franklin
Used x-ray diffraction to study DNA and gain information about it’s structure
http://www.youtube.com/watch?v=VIlF6fovLZE&feature=related
James Watson & Francis Crick
(1953):
Double Helix
model from evidence from Franklins x-ray pattern
Slide1912.3 DNA Replication
Slide20DNA unzips and new base pairs are formed
2 new strands of DNA
Slide21DNA Replication
DNA must get copied BEFORE a cell can divide
Occurs during late
interphase
(S phase)
DNA “unzips” into 2 strands
2 new
complementary strands
are produced
Each new copy has one original strand and one new strand
DNA polymerase
: An enzyme that joins individual nucleotides to produce a new strand of DNA
http://www.youtube.com/watch?v=teV62zrm2P0&feature=related
Slide22Telomeres
Telomeres:DNA at the tips of chromosomes
Very
difficult
to replicate
Telomerase
: a special enzyme to solve this problem by adding short, repeated DNA sequences to the telomeres
Often switched
off
in adult cells
In cancer, telomerase may be activated to enable cancer cells to grow rapidly
Slide23DNA Replication in Prokaryotes and Eukaryotes
Prokaryotes: have a singular, circular DNA
in the
cytoplasm
Begins at a single point
Eukaryotes
:
have 1000x more DNA than prokaryotes
Found in the
nucleus
Packed into chromosomes
DNA and proteins packed together: chromatinCan begin at hundreds of places