Chapter 12
DNA and RNA
transformation, bacteriophage, nucleotide, base pairing,
chromatin, histone, replication, DNA polymerase, gene,
messenger RNA, ribosomal RNA, Transfer RNA,
transcription, RNA polymerase, promoter, intron, exon,
codon, translation, anticodon, mutation, point mutation,
frameshift mutation, polyploidy, adenine, cytosine, deletion,
guanine, nitrogen base, purine, pyrimidine, thymine, uracil
12-1 DNA
12-1 DNA
Frederick Griffith – 1928 – looking at how mice
react to two
related pneumonia bacteria
• Experiment
- Rough bacteria – mice live
- Smooth bacteria – mice got pneumonia & die
- Heat-killed smooth bacteria – mice live
- Heat killed smooth + rough bacteria – mice
got pneumonia & die
12-1 DNA
Figure 12–2 Griffith’s Experiment
Heat-killed,
disease-causing
bacteria (smooth
colonies)
Disease-causing
bacteria (smooth
colonies)
Harmless bacteria Heat-killed, disease(rough colonies) causing bacteria
(smooth colonies)
Dies of pneumonia
Lives
Lives
Control
(no growth)
Harmless bacteria
(rough colonies)
Dies of pneumonia
Live, disease-causing
bacteria (smooth colonies)
12-1 DNA
Figure 12–2 Griffith’s Experiment
• Results = heat killed smooth bacteria
could pass on their trait to harmless
strain… called transformation
Oswald Avery – 1944 – repeated Griffith’s
exp. and found thatDNA was the
transforming factor
12-1 DNA
Alfred Hershey & Martha Chase – 1952 – worked
with bacteria and virus to find out if protein or
DNA held genes
• Virus = DNA/RNA surrounded by a protein coat
• Bacteriophage = a virus that infects bacteria
• Experiment
- Radioactive marker attached to protein part of
bacteriophage… infects bacteria… marker
was seen outside of bacteria
- Radioactive marker to DNA…infection…
marker was seen inside bacteria
12-1 DNA
Figure 12–4 Hershey-Chase
Experiment
Bacteriophage with
phosphorus-32 in
DNA
Phage infects
bacterium
Radioactivity inside
bacterium
Bacteriophage with
sulfur-35 in protein
coat
Phage infects
bacterium
No radioactivity inside
bacterium
• Results = genetic material of bacteriophage
was DNA
12-1 DNA
Components and Structure of DNA
Nucleotides = units (monomers) that make up
DNA molecule
• Made of 3 parts:
- deoxyribose – a 5-carbon sugar
- a phosphate group
- a nitrogenous base
12-1 DNA
• 4 possible nitrogenous bases
- purines: Adenine or Guanine
- pyrimidines: Cytosine or Thymine
Purines
Adenine
Guanine
Phosphate
group
Pyrimidines
Cytosine
Thymine
Deoxyribose
12-1 DNA
Erwin Chargaff – studied amounts of nitrogenous bases in DNA
• % guanine equal to % cytosine
• % adenine equal to % thymine
• also known as base pairing rule: A=T and C=G
Nucleotide
Hydrogen
bonds
Sugar-phosphate
backbone
Key
Adenine (A)
Thymine (T)
Cytosine (C)
Guanine (G)
12-1 DNA
Rosalind Franklin – 1952 – X-ray diffraction to get
pattern from structure of DNA
James Watson & Francis Crick – 1953 –
published model and paper on DNA structure
as a double helix
• double helix is similar to a twisted ladder or
spiral staircase
- deoxyribose and phosphate make up
sides/backbone
- nitrogenous base makes up stairs/rungs
12-2 – Chromosomes and DNA
Replication
Prokaryotes = generally circular strand of DNA in
cytoplasm
Eukaryotes = multiple molecules of DNA in
nucleus
Chromosome
E. coli bacterium
Bases on the chromosome
12-2 Chromosomes and DNA Replication
Chromosome structure
• Chromatin = DNA that is tightly packed around
proteins called histones
- during cell division, chromatin form packed
chromosomes
Chromosome
Nucleosome
DNA
double
helix
Coils
Supercoils
Histones
12-2 Chromosomes and DNA Replication
DNA Replication
• Replication = process of copying DNA
- occurs during S phase of Interphase
- process:
1. DNA is separated into two strands by an
enzyme
2. free nucleotides are added by DNA
polymerase according to base pairing rule
12-2 Chromosomes and DNA Replication
DNA Replication
New strand
Original
strand
DNA
polymerase
Growth
DNA
polymerase
Growth
Replication
fork
Replication
fork
New strand
Original
strand
Nitrogenous
bases
12-3 RNA and Protein Synthesis
12-3 RNA and Protein Synthesis
RNA structure
• Has ribose as a sugar instead of deoxyribose
• Is generally single-stranded
• Has uracil instead of thymine
12-3 RNA and Protein Synthesis
Types of RNA
• All types control protein synthesis in a cell
• 3 main types
- mRNA = messenger RNA – copies of
instructions from DNA
- rRNA = ribosomal RNA – part of
ribosomes
- tRNA = transfer RNA – transfers amino
acids to ribosome
12-3 RNA and Protein Synthesis
RNA
can be
Messenger RNA
also called
Ribosomal RNA
which functions to
mRNA
Carry instructions
also called
which functions to
rRNA
Combine
with proteins
from
to
to make up
DNA
Ribosome
Ribosomes
Transfer RNA
also called
which functions to
tRNA
Bring
amino acids to
ribosome
12-3 RNA and Protein Synthesis
RNA Decoding Chart
12-3 RNA and Protein Synthesis
Figure 12–14 Transcription
• Transcription = process of copying part of
nucleotide Sequence of DNA into a
complementary strand of RNA
• run by enzyme called RNA polymerase
Adenine (DNA and RNA)
Cystosine (DNA and RNA)
Guanine(DNA and RNA)
Thymine (DNA only)
Uracil (RNA only)
RNA
polymerase
DNA
RNA
12-3 RNA and Protein Synthesis
The Genetic Code
• Proteins are chains of amino acids
- 20 different amino acids
- the order or sequence of amino acids
determines properties of the protein
- codon = 3 consecutive nucleotides that
specify a single amino acid
- one amino acid can have multiple codons
start
codon
mRNA
A U G G G C U C C A U C G G C G C A U A A
codon 1
codon 2
codon 3
codon 4
codon 5
codon 6
codon 7
12-3 RNA and Protein Synthesis
Translation
• Translation = the decoding of an mRNA
message into a polypeptide chain (protein)
• Occurs on ribosomes
12-3 RNA and Protein Synthesis
• Process:
- mRNA binds to ribosome
- tRNA brings appropriate amino acid to
ribosome – tRNA has anticodon that is
complementary to codon on mRNA; begins
with specific start codon - AUG
- peptide bonds are made between amino
acids
- assembly line continues until a stop codon
12-3 RNA and Protein Synthesis
Why bother?
• Transcription and translation keep master
plans (DNA) safe in the nucleus, while
blueprints (RNA) are sent to the worksite
(ribosomes)
• Proteins are needed to act as enzymes that
produces the color of your skin, the type of
blood cell, the rate of growth
12-4 Mutations
12-4 Mutations
• Mutation = a change in the genetic
material
• Point mutations = change in one or a few
nucleotides
• Frameshift mutations = adding or deleting
a nucleotide… very disruptive
12-4 Mutations
Chromosomal Mutations
• Chromosomal mutations = change in the
number or structure of chromosomes.
- Deletion = loss of all or part of a chromosome
- Duplication = produce extra copies of parts of
chromosome
Deletion
Duplication
12-4 Mutations
- Inversion = reverse direction of parts of
chromosome
- Translocation = part of one chromosome
breaks and attaches to another
- Polyploidy = an organism has an extra sets
of chromosomes
Inversion
Translocation