Download DNA Replication and Protein Synthesis PPT

Chapter 10 Notes
DNA and RNA
10-1 DNA- History
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Freidrich Miescher (1868) found nuclear material to be ½ protein & ½
unknown substance
1890’s, unknown nuclear substance named DNA
Walter Sutton (1902) discovered DNA in chromosomes
Fredrick Griffith (1928) working with Streptococcus pneumoniae
conducted transformation experiments of virulent & nonvirulent
bacterial strains
Levene (1920’s) determined 3 parts of a nucleotide
Hershey & Chase (1952) used bacteriophages (viruses) to show that
DNA, not protein, was the cell’s hereditary material
Rosalind Franklin (early 1950’s) used x-rays to photograph DNA
crystals
Erwin Chargaff (1950’s) determined that the amount of A=T and
amount of C=G in DNA; called Chargaff’s Rule
Watson & Crick discovered double helix shape of DNA (A pairs with T;
C pairs with G) & built the 1st model
10-1 DNA
In 1928 Fredrick Griffith was studying
the bacteria that cause pneumonia.
- smooth  mouse dies
- rough  mouse lives
- heat killed smooth  mouse lives
- above + rough  mouse dies
10-1 DNA
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)
10-1 DNA
Griffith called this process
transformation: one type of bacteria
turned into another
ex. rough turns into smooth
Avery and other scientists found that DNA
is the nucleic acid that stores and
transmits the genetic information from
one generation to the next
10-2 DNA
The two categories of nitrogenous bases
are purines and pyrimidines
Purines: double ring structure
- adenine and guanine
Pyrimidines: single ring structure
- cytosine and thymine
10-2 DNA
DNA is like a ladder
- the rungs are made of the nitrogenous
bases
- the backbone is formed by the sugar
and phosphate groups
Chargaff’s rule: [A] = [T]; [C] = [G]
10-2 DNA
Purines
Adenine
Guanine
Phosphate
group
Pyrimidines
Cytosine
Thymine
Deoxyribose
10-2 DNA
Nucleotide
Hydrogen
bonds
Sugar-phosphate
backbone
Key
Adenine (A)
Thymine (T)
Cytosine (C)
Guanine (G)
Section Quiz
Avery and other scientists discovered that
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DNA is found in a protein coat.
DNA stores and transmits genetic information from
one generation to the next.
transformation does not affect bacteria.
proteins transmit genetic information from one
generation to the next.
Section Quiz
DNA is a long molecule made of monomers called
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nucleotides.
purines.
pyrimidines.
sugars.
Section Quiz
Chargaff's rules state that the number of guanine
nucleotides must equal the number of
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cytosine nucleotides.
adenine nucleotides.
thymine nucleotides.
thymine plus adenine nucleotides.
Section Quiz
In DNA, the following base pairs occur:
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A
A
A
A
with
with
with
with
C, and G with T.
T, and C with G.
G, and C with T.
T, and C with T.
10-3 Chromosomes and DNA
Replication
Prokaryotes have a single strand of DNA
that forms a circle
- found in the cytoplasm
The DNA of eukaryotes is linear and
forms many strands
- found in the nucleus
10-3 Chromosomes and DNA
Replication
Chromosome
E. Coli Bacterium
Bases on the
Chromosomes
10-3 Chromosomes and DNA
Replication
Eukaryotic DNA is tightly packed to form
chromosomes
- each chromosome contains both DNA
and protein, packed together to form
chromatin.
- the DNA wraps around proteins called
histones
10-3 Chromosomes and DNA
Replication
Chromosome
Nucleosome
DNA
double
helix
Coils
Supercoils
Histones
10-3 Chromosomes and DNA
Replication
DNA Replication: the copying of DNA
before a cell divides
DNA polymerase: the enzyme used in
replication
10-3 Chromosomes and DNA
Replication
During DNA replication, the DNA
separates into two strands, then
produces two new complementary
strands following the rules of base
pairing. Each strand serves as a
template for a new strand.
DNA replication movie
DNA replication movie 2
10-3 Chromosomes and DNA
Replication
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Process by which DNA makes a copy of itself
Occurs during S phase of interphase before cell
division
Extremely rapid and accurate (only 1 in a billion
are incorrectly paired)
Requires many enzymes & ATP (energy)
Begins at special sites along DNA called origins of
replication where 2 strands open & separate
making a replication fork
10-3 Chromosomes and DNA
Replication
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Nucleotides added & new strand forms at
replication forks
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DNA helicase (enzyme) uncoils & breaks the
weak hydrogen bonds between complementary
bases (strands separate)
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DNA polymerase adds new nucleotides to
the exposed bases in the 5’ to 3’ direction
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Leading strand (built toward replication
fork) completed in one piece
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Lagging strand (built moving away from the
replication fork) is made in sections called Okazaki
fragments
10-3 Chromosomes and DNA
Replication
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DNA ligase
helps join Okazaki
segments together
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DNA
polymerase
proofreads the new 1.  Helicase recoils the
two, new identical
DNA checking for
DNA molecules
errors & repairing
them; called excision
repair
10-3 Chromosomes and DNA
Replication
10-3 Chromosomes and DNA
Replication
New strand
Original
strand
DNA
polymerase
Growth
DNA
polymerase
Growth
Replication
fork
Replication
fork
New strand
Original
strand
Section Quiz
In prokaryotic cells, DNA is found in the
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cytoplasm.
nucleus.
ribosome.
cell membrane.
Section Quiz
The first step in DNA replication is
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producing two new strands.
separating the strands.
producing DNA polymerase.
correctly pairing bases.
Section Quiz
A DNA molecule separates, and the sequence
GCGAATTCG occurs in one strand. What is the
base sequence on the other strand?
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GCGAATTCG
CGCTTAAGC
TATCCGGAT
GATGGCCAG
Section Quiz
In addition to carrying out the replication of DNA,
the enzyme DNA polymerase also functions to
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unzip the DNA molecule.
regulate the time copying occurs in the cell cycle.
“proofread” the new copies to minimize the number
of mistakes.
wrap the new strands onto histone proteins.
10-4 RNA and Protein
Synthesis
RNA, like DNA, consists of long chains of
nucleotides.
Three differences between DNA and
RNA
- the sugar is ribose
- single stranded
- contains uracil instead of thymine
*base pairings are A-U and C-G
10-4 RNA and Protein
Synthesis
10-4 RNA and Protein
Synthesis
Genes are coded DNA instructions that
control the production of proteins.
- each gene controls the production of a
specific protein
- DNA (gene)  specific RNA sequence
 specific amino acid sequence
10-4 RNA and Protein
Synthesis
There are three types of RNA:
1. messenger RNA (mRNA)
2. ribosomal RNA (rRNA)
3. transfer RNA (tRNA)
10-4 RNA and Protein
Synthesis
10-4 Messenger RNA (mRNA)
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Single, uncoiled, straight strand of nucleic acid
Found in the nucleus & cytoplasm
Copies DNA’s instructions & carries them to the
ribosomes where proteins can be made
mRNA’s base sequence is translated into the amino
acid sequence of a protein
Three consecutive bases on mRNA called a codon
(e.g. UAA, CGC, AGU)
Reusable
10-4 RNA and Protein
Synthesis
Ribosome
Ribosomal RNA
10-4 Ribosomal RNA (rRNA)
•Globular shape
•Helps make up the
structure of the
ribosomes
•Ribosomes are the
site of translation
(making
polypeptides)
•rRNA & protein make
up the large
•& small subunits of
ribosomes
10-4 RNA and Protein
Synthesis
Amino acid
Transfer RNA
10-4 Transfer RNA (tRNA)
Single stranded molecule containing 80 nucleotides in
the shape of a cloverleaf/hairpin
- Carries amino acids in the cytoplasm to
ribosomes for protein assembly
-Three bases on tRNA that are complementary
to a codon on mRNA are called anticodons (e.g.
codon- UUA; anticodon- AAU)
- Amino Acid attachment site
across from anticodon site on tRNA
-Enters a ribosome & reads mRNA
codons and links together correct
sequence of amino acids to make
a protein
-Reusable
10-4 Transcription
Adenine (DNA and RNA)
Cystosine (DNA and RNA)
Guanine(DNA and RNA)
Thymine (DNA only)
Uracil (RNA only)
RNA
polymerase
DNA
RNA
10-4 Transcription
Transcription: the copying of the DNA into a
complementary strand of RNA
- uses the enzyme RNA polymerase
During transcription, RNA polymerase binds to
DNA and separates the DNA strands. RNA
polymerase then uses one strand of DNA as a
template from which nucleotides are
assembled into a strand of RNA.
The enzyme binds to the region DNA known as
the promoter region.
10-4 Transcription
1.DNA helicase (enzyme) uncoils the DNA molecule
2.RNA polymerase (enzyme) binds to a region of DNA called the promoter
which has the start codon AUG to code for the amino acid methionine
3.Promoters mark the beginning of a DNA chain in prokaryotes, but mark
the beginning of 1 to several related genes in eukaryotes
4.The 2 DNA strands separate, but only one will serve as the template & be
copied
5.Free nucleotides are joined to the template by RNA polymerase in the 5’ to 3’
direction to form the mRNA strand
6.mRNA sequence is built until the enzyme reaches an area on DNA called the
termination signal
7.RNA polymerase breaks loose from DNA and the newly made mRNA
8.Eukaryotic mRNA is modified (unneeded sections snipped out by enzymes &
rejoined) before leaving the nucleus through nuclear pores, but
prokaryotic RNA is not
All 3 types of RNA called transcripts are produced by this method
10-4 RNA and Protein
Synthesis
RNA Editing
Before it leaves the nucleus,
RNA is edited. Splicing
occurs by removing
introns and fusing
exons together.
10-4 RNA and Protein
Synthesis Transcription – Processing of
The Genetic Code
The genetic code is read in
three letter segments
called codons.
There are 64 different
codon possibilities that
code for only 20 amino
acids
-AUG is the start codon
-there are 3 stop codonsUAA, UAG, UGA
Gene Information
10-4 RNA and Protein
Synthesis
Amino Acid
3 Letter
Abbreviation
Codons
Alanine
Ala
GCA GCC GCG GCU
Arginine
Arg
AGA AGG CGA CGC CGG CGU
Aspartic Acid
Asp
GAC GAU
Asparagine
Asn
AAC AAU
Cysteine
Cys
UGC UGU
Glutamic Acid
Glu
GAA GAG
Glutamine
Gln
CAA CAG
Glycine
Gly
GGA GGC GGG GGU
Histidine
His
CAC CAU
Isoleucine
Ile
AUA AUC AUU
Leucine
Leu
UUA UUG CUA CUC CUG CUU
Lysine
Lys
AAA AAG
Methionine
Met
AUG
Phenylalanine
Phe
UUC UUU
Proline
Pro
CCA CCC CCG CCU
Serine
Ser
AGC AGU UCA UCC UCG UCU
Threonine
Thr
ACA ACC ACG ACU
Tryptophan
Trp
UGG
Tyrosine
Tyr
UAC UAU
Valine
Val
GUA GUC GUG GUU
Start
AUG
Stop
UAA UAG UGA
10-4 Translation
Translation: the decoding of mRNA into
an amino acid sequence
During translation, the cell uses
information from messenger RNA to
produce proteins
- anticodon: the three letter sequence
on tRNA that binds with mRNA
10-4 Translation
1. mRNA brings the copied DNA code from the nucleus to the cytoplasm
2. mRNA attaches to one end of a ribosome; called initiation
3. tRNAs attach the correct amino acid floating in the cytoplasm to
themselves
4. tRNA with its attached amino acid has 2 binding sites where they join the
ribosome
5. The tRNA anticodon “reads” & temporarily attaches to the mRNA codon in
the ribosome
6. Two amino acids at a time are linked together by peptide bonds to make
polypeptide -chains (protein subunits); called elongation
7. Ribosomes) move along the mRNA strand until they reach a stop codon
(UAA, UGA, or UAG); called termination
8. tRNA’s break loose from amino acid, leave the ribosome, & return to
cytoplasm to pick up another amino acid
Protein Synthesis – Translation
Animation
10-4 Translation
Phenylalanine
Methionine
Ribosome
mRNA
Start codon
tRNA
Lysine
10-4 Translation
Lysine
tRNA
Translation direction
mRNA
Ribosome
10-4 Translation
Polypeptide
Ribosome
tRNA
mRNA
Section Quiz
The role of a master plan in a building is similar
to the role of which molecule?
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messenger RNA
DNA
transfer RNA
ribosomal RNA
Section Quiz
A base that is present in RNA but NOT in DNA is
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thymine.
uracil.
cytosine.
adenine.
Section Quiz
The nucleic acid responsible for bringing
individual amino acids to the ribosome is
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transfer RNA.
DNA.
messenger RNA.
ribosomal RNA.
Section Quiz
A region of a DNA molecule that indicates to an
enzyme where to bind to make RNA is the
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intron.
exon.
promoter.
codon.