Chapter 12 Notes. A. First Discoveries 1.Griffith- experiment showed that live uncoated bacteria...
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Transcript of Chapter 12 Notes. A. First Discoveries 1.Griffith- experiment showed that live uncoated bacteria...
Chapter 12 Notes
A. First Discoveries1.Griffith- experiment showed that live uncoated bacteria acquired the ability to make coats from dead coated bacteria. He called the process transformation.
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 12-1Figure 12–2 Griffith’s Experiment
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2. Avery- discovered that DNA is the nucleic acid that stores and transmits the genetic information from one generation to the next.
3. Hershey & Chase- used radioactive labeling to identify DNA. They showed that DNA, not protein, is the genetic material of a bacteriophage (virus).
Bacteriophage with phosphorus-32 in DNA
Phage infectsbacterium
Radioactivity inside bacterium
Bacteriophage with sulfur-35 in protein coat
Phage infectsbacterium
No radioactivity inside bacterium
Figure 12–4 Hershey-Chase ExperimentSection 12-1
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DNA Structure1. DNA is composed of subunits called nucleotides.2. Nucleotides have three parts: a) sugar
b) phosphate group c) basea. The sugar is a 5 carbon sugar called deoxyribose.b. There are four kinds of nitrogenous bases- these form the “rungs” of the ladder
1. Adenine 2. Guanine
3. Cytosine4. Thymine
Purines Pyrimidines
Adenine Guanine Cytosine Thymine
Phosphate group Deoxyribose
Figure 12–5 DNA NucleotidesSection 12-1
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DNA Structure
c. The two larger bases- adenine and guanine are called purines.d. The two smaller bases- cytosine and thymine are called
pyrimidines.
e. The backbone of the DNA chain is formed by all sugar and phosphates, the bases hook onto
the sugar part of the chain3. Chargaff’s Rule
a. A (adenine) always equals (joins) to T (thymine)b. G (guanine) always equals (joins) to C (cytosine)
Hydrogen bonds
Nucleotide
Sugar-phosphate backbone
Key
Adenine (A)
Thymine (T)
Cytosine (C)
Guanine (G)
Figure 12–7 Structure of DNASection 12-1
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DNA RNA
4. Rosalind FranklinUsed a technique called X-ray diffraction to
determine DNA was helical.5. Watson and Crick
Built a 3 dimensional model of a DNA molecule which was called a double helix
6. DNA is tightly coiled around a protein called histones. The coil then forms your Chromatin. Coiled chromatin forms your chromosomes.
Figure 12-10 Chromosome Structure of Eukaryotes
Chromosome
Supercoils
Coils
Nucleosome
Histones
DNA
double
helix
Section 12-2
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C. DNA Replication1. Before a cell divides DNA is copied (replicated)2. During DNA replication, the DNA molecule separates into 2 strands. Each new strand will hook up with it’s complementary base partner, making 2 new complementary strands. The strands follow Chargaff’s rule on base pairing.
3. The sites where separation and replication occur are called replication forks.
4. The replication is carried out by enzymes that “unzip” the DNA called DNA polymerase.
Figure 12–11 DNA ReplicationSection 12-2
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Growth
Growth
Replication fork
DNA polymerase
New strand
Original strand DNA
polymerase
Nitrogenous bases
Replication fork
Original strand
New strand
DNA
DNA Replication• Complementary base pairs form new strands.
DNA
from to to make up
Concept MapSection 12-3
also called which functions to also called also called which functions towhich functions to
can be
RNA
Messenger RNA Ribosomal RNA Transfer RNA
mRNA Carry instructions rRNACombine
with proteins tRNABring
amino acids toribosome
DNA Ribosome Ribosomes
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III. RNA Structure
A. RNA Structure1. Nucleic Acid made of single chains of
nucleotides2. The sugar is called Ribose3. Base pairs are cytosine & guanine,
adenine & Uracil.4. Uracil replaces the Thymine
B. Types of RNA1. Messenger RNA (mRNA)- carries the instructions to make a particular protein from DNA2. Ribosomal RNA (rRNA)- makes up the major part of ribososmes3. Transfer RNA (tRNA)- transfers the amino acids to ribosomes during protein synthesis
III. Transcription
A. The process of producing mRNA from DNA.1. RNA polymerase binds to the DNA and separates the strands.2. RNA polymerase uses one strand of DNA as a template to form a strand of mRNA.3. RNA polymerase enzymes will only bind to regions of DNA called promoters (it has a specific base sequence).
RNADNA
RNApolymerase
Figure 12–14 TranscriptionSection 12-3
Adenine (DNA and RNA)Cystosine (DNA and RNA)Guanine(DNA and RNA)Thymine (DNA only)Uracil (RNA only)
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B. RNA Editing
1. Intron- intervening sequences that are removed from the mRNA molecules before they become functional.
2. Exons- the remaining portions that are spliced back together to form the final mRNA.
IV. Genetic Code
A. Three bases long, called codons (Ex. GCA)B. Proteins are made of long chains called
polypeptidesC. Codons specify a single amino acid that is to
be added to the polypeptideD. D. Polypeptides are made by joining the
amino acids.
Figure 12–17 The Genetic Code
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V. Translation (Protein synthesis)A. The decoding of an mRNA message into a proteinB. Takes place in the ribosomesC. Steps involved:
1. mRNA is transcribed from DNA and released in the cytoplasm2. Translation begins when mRNA attaches to a ribosome in the cytoplasm at the start codon (AUG)3. Each transfer RNA as an anticodon whose bases are complementary to a codon on the mRNA. This has an amino acid attached to one end.
4. The ribosome positions the start codon to attract its anticodon, which is part of tRNA and binds them together.
5. Once the first and second codon and anticodon are bound, the ribosome joins the two amino acids and the tRNA breaks away.
6. Chains of amino acids continue to grow until the ribosome reaches a stop codon on the mRNA strand. Then it replaces the chain.
Messenger RNA
Messenger RNA is transcribed in the nucleus.
Transfer RNA
The mRNA then enters the cytoplasm and attaches to a ribosome. Translation begins at AUG, the start codon. Each transfer RNA has an anticodon whose bases are complementary to a codon on the mRNA strand. The ribosome positions the start codon to attract its anticodon, which is part of the tRNA that binds methionine. The ribosome also binds the next codon and its anticodon.
mRNA Start codon
Ribosome
Methionine
Phenylalanine tRNALysine
Nucleus
Figure 12–18 TranslationSection 12-3
mRNA
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The Polypeptide “Assembly Line”The ribosome joins the two amino acids—methionine and phenylalanine—and breaks the bond between methionine and its tRNA. The tRNA floats away, allowing the ribosome to bind to another tRNA. The ribosome moves along the mRNA, binding new tRNA molecules and amino acids.
mRNARibosome
Translation direction
Lysine tRNA
tRNA
Ribosome
Growing polypeptide chain
mRNA
Completing the PolypeptideThe process continues until the ribosome reaches one of the three stop codons. The result is a growing polypeptide chain.
Figure 12–18 Translation (continued)Section 12-3
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http://www.pbs.org/wgbh/aso/tryit/dna/#
Substitution InsertionDeletion
Gene Mutations:Substitution, Insertion, and Deletion
Section 12-4
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Deletion
Duplication
Inversion
Translocation
Figure 12–20 Chromosomal Mutations
Section 12-4
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