dna and rna
DESCRIPTION
Chapter 12. DNA and RNA. 1928 – Griffith Discovered bacteria transferred something between them that changed them into a new strain. Called this “bacterial transformation”. Historical Development. Griffith’s Experiment. Section 12-1. - PowerPoint PPT PresentationTRANSCRIPT
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DNA AND RNAChapter 12
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HISTORICAL DEVELOPMENT
1928 – Griffith Discovered
bacteria transferred something between them that changed them into a new strain.
Called this “bacterial transformation”.
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Disease-causing bacteria (smooth
colonies)
Harmless bacteria (rough colonies) Heat-killed,
disease-causing bacteria (smooth colonies)
Control(no growth)
Heat-killed, disease-causing bacteria (smooth colonies)
Harmless bacteria (rough colonies)
Dies of pneumonia Lives Lives Live, disease-causingbacteria (smooth colonies)
Dies of pneumonia
Section 12-1
GRIFFITH’S EXPERIMENT
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HISTORICAL DEVELOPMENT 1944 – Avery
Determined the transforming factor was DNA.
He destroyed different parts of the bacteria, and only when the DNA was destroyed did transformation not
occur.
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HISTORICAL DEVELOPMENT 1952 – Hershey and Chase
Using a blender and bacteriophage, determined that DNA, not protein, was the genetic material.
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Bacteriophage with phosphorus-32 in DNA
Phage infectsbacterium
Radioactivity inside bacterium
Bacteriophage with sulfur-35 in protein coat
Phage infectsbacterium
No radioactivity inside bacterium
HERSHEY-CHASE EXPERIMENT
Section 12-1
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Bacteriophage with phosphorus-32 in DNA
Phage infectsbacterium
Radioactivity inside bacterium
Bacteriophage with sulfur-35 in protein coat
Phage infectsbacterium
No radioactivity inside bacterium
Section 12-1
HERSHEY-CHASE EXPERIMENT
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Bacteriophage with phosphorus-32 in DNA
Phage infectsbacterium
Radioactivity inside bacterium
Bacteriophage with sulfur-35 in protein coat
Phage infectsbacterium
No radioactivity inside bacterium
Section 12-1
HERSHEY-CHASE EXPERIMENT
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HISTORICAL DEVELOPMENT 1952 – Rosalind
Franklin Used x-ray
crystallography to show the structure of DNA was a helix.
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HISTORICAL DEVELOPMENT
1953 – Watson and Crick Determined the
structure of DNA was a double helix, and proposed a model for DNA replication.
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DNA STRUCTURE DNA is a chain (polymer) of
nucleotides. A nucleotide consists of a sugar, phosphate
and nitrogenous base.
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Purines PyrimidinesAdenine Guanine Cytosine Thymine
Phosphate group Deoxyribose
DNA NUCLEOTIDESSection 12-1
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DNA STRUCTURE DNA is a double helix (twisted ladder).
Two nucleotide polymers are held together by weak hydrogen bonds.
Nitrogen bases always pair up this way: Adenine with thymine A-T Cytosine with guanine C-G
The backbone of the ladder is alternating sugars and phosphates.
The steps of the ladder are the base pairs.
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Hydrogen bonds
Nucleotide
Sugar-phosphate backbone Key
Adenine (A)Thymine (T)Cytosine (C)Guanine (G)
STRUCTURE OF DNASection 12-1
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CHROMOSOMES AND DNA REPLICATION
12-2
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DNA AND CHROMOSOMES Prokaryotic cells (bacteria)
No nucleus Single circular chromosome Bacterial DNA is about 1.6mm long
Eukaryotic cells (all else) 1000X more DNA than bacteria DNA in nucleus (protected) Multiple chromosomes Human DNA (combined) is over 1 meter long
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Chromosome
E. coli bacteriumBases on the chromosome
PROKARYOTIC CHROMOSOME STRUCTURE
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DNA AND CHROMOSOMES Eukaryotic DNA is tightly packed and
folded. It is wound about proteins called
histones.
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Chromosome Structure of Eukaryotes
Chromosome
Supercoils
Coils
Nucleosome
Histones
DNAdoublehelix
Section 12-2
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DNA Packing
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DNA REPLICATION A cell copies its DNA before dividing.
The DNA uncoils. Then it “unzips” – the two strands separate
along the weak hydrogen bonds. Complimentary nucleotides are added with
the help of the enzyme DNA Polymerase. The result: two identical molecules of DNA.
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DNA REPLICATIONSection 12-2
Growth
Growth
Replication fork
DNA polymerase
New strandOriginal strand DNA
polymerase
Nitrogenous bases
Replication fork
Original strand
New strand
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DNA REPLICATION C:\Users\Carolyn\Videos\RealPlayer Do
wnloads\How DNA Copies Itself.mp4
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RNA AND PROTEIN SYNTHESIS12-3
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BIG IDEA DNA makes RNA makes Proteins makes
You.
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RNA STRUCTURE Single-stranded chain of nucleotides No thymine - its replaced by uracil Sugar is ribose, not deoxyribose
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TYPES OF RNA Messenger RNA (mRNA)
Carries a copy of the genetic code (gene) for a protein into the cytoplasm.
Ribosomal RNA (rRNA) A component of ribosomes where proteins
are made. Transfer RNA (tRNA)
Carries amino acids to the ribosome for assembly into proteins.
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TRANSCRIPTION The process of DNA making mRNA in the
nucleus is called transcription. A section of DNA (gene) unwinds and separates Enzymes add complimentary RNA nucleotides
to make mRNA. mRNA leaves the nucleus and goes to a
ribosome in the cytoplasm. What is the complimentary nucleotide sequence for
this DNA sequence? DNA = A-T-T-C-G-C-G
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RNADNA
RNApolymerase
TRANSCRIPTIONAdenine (DNA and RNA)Cystosine (DNA and RNA)Guanine(DNA and RNA)Thymine (DNA only)Uracil (RNA only)
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TRANSCRIPTION C:\Users\Carolyn\Videos\RealPlayer Do
wnloads\Transcription.flv
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TRANSLATION The process of mRNA being read on a ribosome
to make a protein is called translation. mRNA attaches to a ribosome. tRNA carries amino acids to the ribosome. The mRNA codon (3 nucleotide sequence) matches
up with a complimentary tRNA anticodon (complimentary sequence).
The amino acid is dropped off and added the growing polypeptide chain.
What is the amino acid sequence for the following mRNA sequence? See the universal genetic code chart…
mRNA = AUAAGCGCU
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THE GENETIC CODE
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TRANSLATION
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FIGURE 12–18 TRANSLATION (CONTINUED)
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TRANSLATION C:\Users\Carolyn\Videos\RealPlayer Do
wnloads\Translation.flv
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TRANSCRIPTION AND TRANSLATION C:\Users\Carolyn\Videos\RealPlayer Do
wnloads\From DNA to Protein.mp4
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TRANSCRIPTION AND TRANSLATION C:\Users\Carolyn\Videos\RealPlayer Do
wnloads\DNA Transcription and Protein Assembly.mp4
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GENES AND PROTEINS Proteins are made of several
polypeptide chains folded together. The shape is important to how the protein
functions. One gene codes for the production of
one polypeptide. Therefore, several genes are needed to
make one protein.
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GENE MUTATIONS12-4
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KINDS OF MUTATIONS Mistakes made when DNA is copied are
called mutations. Two kinds: gene and chromosome
mutations
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GENE MUTATIONS Gene mutations affect only one gene.
There is a change in the sequence of bases in DNA.
This causes the protein made by that gene to be incorrect. (sometimes)
Ex: lactose intolerance
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CHROMOSOME MUTATIONS Changes in the number or structure of
chromosomes are called chromosome mutations. Ex: An extra chromosome causes Down
Syndrome.
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MUTAGENS Substances that can cause mutations
are called mutagenic agents. UV light, chemicals, radiation
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SIGNIFICANCE OF MUTATIONS• Inherited only if the mutation occurs in a sex
cell. Harmful mutations – cause many genetic
disorders. Ex: cystic fibrosis
Neutral mutations – have no effect on gene expression or protein function (most).
Beneficial mutations – source of genetic variability. Breeders artificially select for these traits