Chapter 12 Notes

1
Chapter 12 Notes
2
A. First Discoveries

• Griffith- experiment showed that live uncoated
• bacteria acquired the ability to make coats
• from dead coated bacteria. He called the
• process transformation.

3
Figure 122 Griffiths Experiment
Section 12-1
Heat-killed, disease-causing bacteria (smooth
colonies)
Harmless bacteria (rough colonies)
Control(no growth)
Harmless bacteria (rough colonies)
Heat-killed, disease-causing bacteria (smooth
colonies)
Disease-causing bacteria (smooth colonies)
Dies of pneumonia
Dies of pneumonia
Lives
Lives
Live, disease-causingbacteria (smooth colonies)
Go to Section
4

• 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).

5
Figure 124 Hershey-Chase Experiment
Section 12-1
Bacteriophage with phosphorus-32 in DNA
Phage infectsbacterium
Radioactivity inside bacterium
Bacteriophage with sulfur-35 in protein coat
Phage infectsbacterium
No radioactivity inside bacterium
Go to Section
6
DNA Structure

• 1. DNA is composed of subunits called
  nucleotides.
• Nucleotides have three parts a) sugar
• b)
  phosphate group
  c) base
• a. 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. Cytosine
• 4. Thymine

7
Figure 125 DNA Nucleotides
Section 12-1
Purines
Pyrimidines
Adenine
Guanine
Cytosine
Thymine
Phosphate group
Deoxyribose
Go to Section
8
DNA Structure
9

• 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 chain
• 3. Chargaffs Rule
• a. A (adenine) always equals (joins) to T
  (thymine)
• b. G (guanine) always equals (joins) to C
  (cytosine)

10
Figure 127 Structure of DNA
Section 12-1
Nucleotide
Hydrogen bonds
Sugar-phosphate backbone
Key Adenine (A) Thymine (T) Cytosine (C) Guanine
(G)
Go to Section
11
DNA RNA
12

• 4. Rosalind Franklin
• Used 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.

13
Figure 12-10 Chromosome Structure of Eukaryotes
Section 12-2
Nucleosome
Chromosome
DNA double helix
Coils
Supercoils
Histones
Go to Section
14

• C. DNA Replication
• 1. 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 its complementary base partner,
  making 2 new complementary strands. The strands
  follow Chargaffs 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.

15
Figure 1211 DNA Replication
Section 12-2
Original strand
DNA polymerase
New strand
Growth
DNA polymerase
Growth
Replication fork
Replication fork
Nitrogenous bases
New strand
Original strand
Go to Section
16
DNA
17
DNA Replication

• Complementary base pairs form new strands.

18
DNA
19
Concept Map
Section 12-3
RNA
can be
also called
which functions to
also called
also called
which functions to
which functions to
from
to
to make up
Go to Section
20
III. RNA Structure

• A. RNA Structure
• 1. Nucleic Acid made of single chains of
  nucleotides
• 2. The sugar is called Ribose
• 3. Base pairs are cytosine guanine, adenine
  Uracil.
• 4. Uracil replaces the Thymine

21

• B. Types of RNA
• 1. Messenger RNA (mRNA)- carries the
  instructions to make a particular protein from
  DNA
• 2. Ribosomal RNA (rRNA)- makes up the major
  part of ribososmes
• 3. Transfer RNA (tRNA)- transfers the amino
  acids to ribosomes during protein synthesis

22
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).

23
Figure 1214 Transcription
Section 12-3
Adenine (DNA and RNA) Cystosine (DNA and
RNA) Guanine(DNA and RNA) Thymine (DNA
only) Uracil (RNA only)
RNApolymerase
DNA
RNA
Go to Section
24
(No Transcript)
25
B. RNA Editing

• 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.

26
IV. Genetic Code

• Three bases long, called codons (Ex. GCA)
• B. Proteins are made of long chains called
  polypeptides
• Codons specify a single amino acid that is to be
  added to the polypeptide
• D. Polypeptides are made by joining the amino
  acids.

27
Figure 1217 The Genetic Code
Go to Section
28
(No Transcript)
29
V. Translation (Protein synthesis)

• A. The decoding of an mRNA message into a
  protein
• B. Takes place in the ribosomes
• Steps involved
• 1. mRNA is transcribed from DNA and released in
  the cytoplasm
• 2. 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.

30

• The ribosome positions the start codon to attract
  its anticodon, which is part of tRNA and binds
  them together.
• Once the first and second codon and anticodon are
  bound, the ribosome joins the two amino acids and
  the tRNA breaks away.
• Chains of amino acids continue to grow until the
  ribosome reaches a stop codon on the mRNA strand.
  Then it replaces the chain.

31
Figure 1218 Translation
Section 12-3
Nucleus
Messenger RNA Messenger RNA is transcribed in
the nucleus.
mRNA
Lysine
Phenylalanine
tRNA
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.
Methionine
Ribosome
Start codon
mRNA
Go to Section
32
Figure 1218 Translation (continued)
Section 12-3
The Polypeptide Assembly Line The ribosome
joins the two amino acidsmethionine and
phenylalanineand 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.
Growing polypeptide chain
Ribosome
tRNA
Lysine
tRNA
mRNA
Completing the Polypeptide The process continues
until the ribosome reaches one of the three stop
codons. The result is a growing polypeptide
chain.
mRNA
Translation direction
Ribosome
Go to Section
33
http//www.pbs.org/wgbh/aso/tryit/dna/
34
Gene MutationsSubstitution, Insertion, and
Deletion
Section 12-4
Deletion
Substitution
Insertion
Go to Section
35
Figure 1220 Chromosomal Mutations
Section 12-4
Deletion
Duplication
Inversion
Translocation
Go to Section