Chapter 12 DNA & RNA
Jan 16, 2016
Chapter 12
DNA & RNA
I.DNA
A. Griffith & TransformationFrederick Griffith was trying to figure out how bacteria
made people sick-how they cause a certain type of pneumonia.
He isolated 2 strains(types) from mice-both cultured well,but only one caused pneumonia.The culture of the disease causing bacteria were __________________colonies while the other was
rough.
smooth
1-Griffith’s experiments (1928) Mice injected w/ disease –causing strain got sick
and died and nothing happened if injected w/other strain…He wondered if the disease-causing type made a toxin…?
So he took some of disease strain and heated to kill bacteria and then injected into mice….mice survived suggesting it was not a toxin producing disease
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
Figure 12–2 Griffith’s Experiment
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
Figure 12–2 Griffith’s Experiment
2-Transformation He mixed his heat –killed w/ live harmless bacteria and
injected into mice…..________________________ Somehow the disease –causing strain passed their
disease capacity to harmless bacteria….. disease –causing strain found in lungs
He called this changing of one bacteria by the genes of another _____________________....Thus a factor(gene) from heat killed disease –causing strain was passed on.
Mice developed pneumonia transformation
B. Avery & DNA
Team of scientists lead by Avery in 1944 repeated Griffith’s experiment in order to determine which molecule was responsible for the transformation.
They made an extract from the heat-killed bacteria and treated it w/enzymes that kill proteins,lipids and other molecules,inc. RNA
Avery cont’d
____________________still occurred so the above molecules were not responsible for transformation
They repeated the experiment but used enzymes that kill____________, stopping transformation….
Therefore ________caused the transformation and thus stores and transmits genetic info
transformation
DNA
C. The Hershey –Chase Experiment
1952-Alfred Hershey and Martha Chase studied viruses-disease-causing particles smaller than a cell.
______________________-virus that infects bacteria.They have a DNA or RNA core and a protein coat…They attach to the surface of a bacterium and inject genetic info into cell.The viral genes act to produce many new bacteriophages and eventually destroy bacterial cell,w/_____________bursting out.
bacteriophageviruses
They grew viruses in cultures containing _________________________________,mixed them w/bacteria and waited a few min. for viruses to inject genetic material.
Then they separated the bacteria from the viruses and tested bacteria for radioactive marker…..nearly all the radioactivity was P-32-found in _________----thus concluding it was the genetic material was DNA !
Radioactive markers
DNA
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
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
Figure 12–4 Hershey-Chase Experiment
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
Figure 12–4 Hershey-Chase Experiment
D. The Components and Structure of DNA
Scientists questioned how the DNA molecule could do three things 1)carry info from 1 generation to the next 2)putting that info to work and 3)could be easily copied
DNA is a long molecule made of units called ___________________________________________-
nucleotides
The nucleotide is made of 3 basic parts:______________________(sugar), a phosphate group and a_________________________________
deoxyribose Nitrogenous base
2 nitrogenous bases are purines(have 2 rings):___________________________(A)and_______(G)
2 other nitrogenous bases are pyrimidines (have 1 ring):____________________(C)and
____________________________(T)
Adenine ,guanine
Cytosine and thymine
--backbone made by sugar and phosphate w/ bases sticking out sideways
Purines Pyrimidines
Adenine Guanine Cytosine Thymine
Phosphate group Deoxyribose
Figure 12–5 DNA Nucleotides
Section 12-1
1-_______________________Rules-discovered that %’s of Cytosine and guanine were almost equal in DNA and the same was true for adenine and thymine….Thus A pairs w/T and C w/ G-BASE PAIRING
Chargaff’s Rules
Percentage of Bases in Four OrganismsSection 12-1
Source of DNA A T G CSource of DNA A T G C
Streptococcus 29.8 31.6 20.5 18.0
Yeast 31.3 32.9 18.7 17.1
Herring 27.8 27.5 22.2 22.6
Human 30.9 29.4 19.9 19.8
Streptococcus 29.8 31.6 20.5 18.0
Yeast 31.3 32.9 18.7 17.1
Herring 27.8 27.5 22.2 22.6
Human 30.9 29.4 19.9 19.8
2- X-ray evidence-1950’s –Rosalind Franklin used X-ray diffraction to learn about DNA structure----The scattered X pattern seen begins to show the __________-partial TWISTED STRUCTURE of DNA
helix
3---Double helix_ Watson and Crick -2 strands wound around each
other---like the twisted ladder or spiral staircase Strands held together by H-bonds
Hydrogen bonds
Nucleotide
Sugar-phosphate backbone
Key
Adenine (A)
Thymine (T)
Cytosine (C)
Guanine (G)
Figure 12–7 Structure of DNA
Section 12-1
Interest Grabber
A Perfect Copy
When a cell divides, each daughter cell receives a complete set of chromosomes. This means that each new cell has a complete set of the DNA code. Before a cell can divide, the DNA must be copied so that there are two sets ready to be distributed to the new cells.
Section 12-2
I
Section 12-2
1. On a sheet of paper, draw a curving or zig-zagging line that divides the paper into two halves. Vary the bends in the line as you draw it. Without tracing, copy the line on a second sheet of paper.
2. Hold the papers side by side, and compare the lines. Do they look the same?
3. Now, stack the papers, one on top of the other, and hold the papers up to the light. Are the lines the same?
4. How could you use the original paper to draw exact copies of the line without tracing it?
5. Why is it important that the copies of DNA that are given to new daughter cells be exact copies of the original?
II. Chromosomes & DNA Replication
A-DNA & ChromosomesIn cytoplasm in prokaryotesIn _______________________found in cell
nucleus in the form of a number of chromosomes(46 humans,8 Drosophilia and 22 Sequoia trees)
eukaryotes
1--DNA length 1.6 mm in E.coli(has 4,639,221 base pairs)---
obviously it must be tightly folded
2-Chromosome Structure Eukaryotic cells have about 1000 times as many
base pairs of DNA than a bacterium Humans cells have ~ 1 m DNA Eukaryotic chromosomes contain DNA and a
protein ,which together make _____________________-consisting of DNA tightly packed around proteins called histones
chromatin
DNA and histone together make beadlike_____________________________
Nucleosomes pack together to make thick fibers,drawn together during mitosis…also separating
Role of nucleosomes-fold great lengths of DNA into tiny spaces
nucleosomes
Chromosome
E. coli bacterium
Bases on the chromosome
Prokaryotic Chromosome StructureSection 12-2
Figure 12-10 Chromosome Structure of Eukaryotes
Chromosome
Supercoils
Coils
Nucleosome
Histones
DNA
double
helix
Section 12-2
B. DNA Replication
Each strand of DNA double helix has all the info to___________________________by base pairing
Strands are complementary In prokaryotes,this begins @single point and
proceeds-often in 2 directions In Eukaryotes,DNA replication begins @ 100’s of
places,going both directions until complete __________________________is where replication
occurs
Reconstruct the other half
Replication fork
1-Duplicating DNA __________________________or duplication of
DNA happens before cell division---ensuring each cell has a complete set of DNA molecules
Each strand of a double helix serves as a _____________________or model for new strand
A pairs w/ T and C w/ G
replication
template
2-How Replication Occurs Carried out by a series of enzymes that unzip a
molecule ____________________________________ joins
individual nucleotides to make a DNA molecule….also proof reads the new strands
DNA polymerase
Figure 12–11 DNA Replication
Section 12-2
Growth
Growth
Replication fork
DNA polymerase
New strand
Original strand DNA
polymerase
Nitrogenous bases
Replication fork
Original strand
New strand
III. RNA & Protein Synthesis
The double helix structure explains how DNA is copied,but not how a gene works-_______________are coded DNA instructions that control the production of protein in the cell.
A) The structure of RNA Long chain of nucleotides 3 main differences between DNA & RNA:
1--Sugar is _________________ 2---Generally single-stranded 3---RNA contains ________________(U) in
place of thymine (T)
genes
uracil ribose
B. Types of RNA
Main job=_________________-ie the assembly of amino acids into proteins
3 Types: ____________________(mRNA)-carry copies for
instructions from DNA to rest of cell ____________________(rRNA)-type of RNA that helps
make up ribosomes,where proteins assembled ________________(tRNA)transfers each amino acid to
the ribosome as it is coded for on mRNA.
Protein synthesis
messenger
ribosomal Transfer
from to to make up
Concept MapSection 12-3
also called which functions to
also called also called which functions to
which functions to
can be
RNA
Messenger RNA Ribosomal RNA Transfer RNA
mRNA Carry instructions rRNACombine
with proteins tRNABring
amino acids toribosome
DNA Ribosome Ribosomes
C. Transcription-produces RNA molecules by copying part of nucleotide sequence of DNA into a complementary sequence in RNA
Requires enzyme known as _______________________________________-binds to DNA and separates DNA strands.Then uses one strand as template to make RNA
The enzyme only binds to areas known as promoters-signals that indicate where to make RNA.Similar signals tell where to stop
RNA-polymerase
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)
D. RNA editing
________________________ in eukaryotic genes ,sequences of nucleotides that ARE NOT involved in coding for proteins
_______________________-DNA sequence that does code for protein
introns
exons
E. Genetic Code
______________________-chain of amino acids=proteins
_________________-3 consecutive nucleotides that specify a specific amino acid
Example –UCGCACGGU reads UCG_CAC_GGU and codes for Serine-Histidine-Glycine
polypeptide
codon
The Genetic Code
Section 12-3
Universal code64 possible 3 base codonsAUG can specify methionine or start
codon3 stop codons that do not code for an
amino acid
F. Translation
______________________reads the instructions for the order in which amino acids should be joined by reading mRNA
____________________________is the decoding of an mRNA message into a polypeptide(protein)
Before translation occurs,mRNA is transcribed from DNA and released into __________________________.
Translation begins when mRNA molecule in cytoplasm attaches to a _____________________.
ribosome
translation
cytoplasm
ribosome
As each codon of the mRNA moves through the moves through the ribosome,_____________brings in the proper,indicated amino acid and transferred to polypeptide chain
Each tRNA carries one kind of amino acid__________________ is a group of 3 bases on a
tRNA that are complementary to a mRNA codonRibosome forms a _________________bond
between amino acids and breaks tRNA bond releasing it
Protein keeps growing until ribosome reaches stop codon on mRNA
tRNA
anticodonpeptide
Figure 12–18 TranslationSection 12-3
Figure 12–18 Translation (continued)Section 12-3
Mutations=________________________
A.---Kinds of Mutations 1) ________________________________-changes in a
single gene _____________________________________-changes in 1 or
a few nucleotides-@ a single point in DNA-includes substitutions,insertions and deletions
Substitutions usually affect no more than 1 amino acid ____________________________________-insertions or
deletions where the reading frame of the codon message is changed-can VERY much alter or even stop the function of a protein
Changes in genetic material
Point mutation
Frameshift mutation
Gene mutation
2)Chromosomal Mutations-change in the # or structure of chromosomes-can change the location of genes on chromosomes and /or number of copies of some genes.
4 types-1)Deletions-loss of all or part of a chromosome
2)__________________-extra copies of a part of a chromosome
3)________________reverse directions of parts of chromosomes
4)____________-part of one chromosome breaks off and attaches to another
duplication
inversions
translocations
Substitution InsertionDeletion
Gene Mutations: Substitution, Insertion, and Deletion
Section 12-4
Deletion
Duplication
Inversion
Translocation
Figure 12–20 Chromosomal Mutations
Section 12-4
B. Significance of Mutations
Many have no effectHarmful effects include genetic disorders and cancer________________________-contains extra set of
chromosomes-bad in most cases but often helpful in PLANTS.
polyploidy
V. Gene Regulation
Only a fraction of a gene expressed at one time ___________________-group of genes that
operate together ________________-where repressor binds operon
(when it)is turned off Operons not usually found in eukaryotes-these
genes are usually controlled individually and regulation more complex---mainly because of cell specialization
Hox genes-control differentiation of cells and tissues in the embryo
operon
operator
Regulatory sites
Promoter(RNA polymerase binding site)
Start transcription
DNA strand
Stop transcription
Typical Gene StructureSection 12-5
Karyotypes