Download Chapter 10: Nucleic Acids And Protein Synthesis

Chapter 10: Nucleic Acids
And Protein Synthesis
Essential Question: What roles do
DNA and RNA play in storing
genetic information?
I. DNA: Deoxyribonucleic acid
A. Function
1. DNA stores and transmits the genetic
information that tells cells which proteins to make
2. Proteins form the structural units
of cells and control chemical
processes in cells
B. Structure of DNA
1. Made of repeating units called nucleotides
a) Sugar: deoxyribose
b) Phosphate group
c) Nitrogen-containing bases DNA
2. Four types of nitrogen bases
a) Adenine: A
c) Cytosine: C
b) Guanine: G
d) Thymine: T
3. Nitrogen bases can be put into two groups
a) Purines: double ring of carbon and
nitrogen atoms (adenine and guanine)
b) Pyrimidines: single ring of carbon and
nitrogen atoms (cytosine and thymine)
DNA Nucleotides
Section 12-1
Purines
Adenine
Guanine
Phosphate
group
Go to
Section:
Pyrimidines
Cytosine
Thymine
Deoxyribose
C. Double helix: two nucleotide chains that wrap
around each other to form a double spiral
1. Model of DNA by Watson
and Crick in 1953
2. Watson and Crick used
X-ray pictures from Rosalind
Franklin to help create their model
D. Complementary Base Pairing: uses a
hydrogen bond to connect bases
1. Adenine pairs with thymine
2. Guanine pairs with cytosine
3. Base sequence: order of nitrogenous bases on
a chain of DNA
4. A C C T G T G A G A C
TGGACACTCTG
Base Pairing
Section 12-1
Structure of DNA
Nucleotide
Hydrogen
bonds
Sugar-phosphate
backbone
Key
Adenine (A)
Thymine (T)
Cytosine (C)
Guanine (G)
Go to
Section:
DNA review
Build a DNA model
E. Replication of DNA: process of copying DNA in a
cell
1. DNA unwinds
a) replication fork: point at which the two
chains separate
b) helicases: enzyme that separates the strands and
breaks the hydrogen bonds
2. Each chain serves as a template
for a new nucleotide
3. DNA polymerase: enzyme used to add new chains
of DNA using nucleotides that are complementary
to the existing DNA chains
a) Nucleotides are joined between the sugars and
phosphate groups
b) The bases bond to bases on the original strand
c) If original strand bases are A T T C C then the
new strand are
TAAGG
4. Replication can begin at many points along the DNA
strand
5. High degree of accuracy: 1 error every 10,000 paired
nucleotides
6. Mutation: change in the nucleotide sequence
and can cause serious effects in cells
a) Proofreading enzymes can detect errors in
the base pairing and repair enzymes can fix
the error
b) 1 error per 1 billion nucleotides
c) DNA can also be damaged by chemicals and
ultraviolet radiation from the sun
d) Mutations can cause cancer if the genes
effected control how a cell divides
7. When replication is complete,
two new exact copies of the
original DNA molecule are produced
Replication
Review
DNA: double helix, made up of nucleotides
(sugar, phosphate, and base)
4 Bases: A=T, C=G
Replication: makes a copy of the DNA using
helicase and DNA polymerase
Section 12-2
DNA Replication
New strand
Original
strand
DNA
polymerase
Growth
DNA
polymerase
Growth
Replication
fork
Replication
fork
New strand
Go to
Section:
Original
strand
Nitrogenous
bases
II. Protein synthesis
A. Flow of genetic information
1.Gene determines a person’s hair color
2. Gene directs the making of a protein (pigment in
hair)
3. Protein is made by RNA
4. Steps involved
a) transcription: DNA makes RNA
b) translation: RNA makes the protein
c) protein gives the characteristic
Protein tour
B. RNA Function
1. RNA carries the genetic information from the
nucleus to the cytoplasm
2. The proteins are then made in the cytoplasm
C. Structure of RNA
1. Made of repeating nucleotides
2. Sugar: ribose
3. Bases: Uracil replaces thymine so uracil will pair
with adenine
4. Single strand
Compare DNA to RNA
D. Types of RNA: each has a different function
1. Messenger RNA (mRNA): carries genetic
information from the DNA in the nucleus to the
cytoplasm
2. Transfer RNA (tRNA): strand folded into a
hairpin shape that binds to specific amino acids
3. Ribosomal RNA (rRNA): globular form that
combines with proteins to make the ribosomes
where proteins will be made
RNA types
E. Transcription: process by which genetic
information is copied from DNA to RNA
1. RNA polymerase: enzyme that makes RNA
copies of specific sequences of DNA
2. Promoters: region of DNA that marks the
beginning of the DNA chain that will be transcribed
3. Steps
a) RNA polymerase
binds to promoters
b) DNA strands are separated
c) RNA polymerase begins adding
complementary RNA nucleotides using one DNA
strand as a template
d) Continues until the polymerase reaches a DNA
region called the termination signal
4. Termination signal: specific sequence of
nucleotides that marks the end
5. RNA polymerase releases the DNA and newly
formed RNA
6. All three forms of RNA are made by this process
7. mRNA will move through the pores of the nucleus
into the cytoplasm and direct the making of the
proteins
Section 12-3
Transcription
Adenine (DNA and RNA)
Cystosine (DNA and RNA)
Guanine(DNA and RNA)
Thymine (DNA only)
Uracil (RNA only)
RNA
polymerase
DNA
RNA
Go to
Section:
F. Genetic Code: nucleotides in mRNA that determine
the sequence of amino acids in proteins
1. Codon: 3 mRNA nucleotides that are read
together to determine a specific amino acid
2. Several codons code for each amino acid
3. Start codon: AUG : tells the ribosome to start
translating
4. Stop codons: UAA, UAG, UGA:
causes the ribosome to stop translating
Codon
Section 12-3
Go to
Section:
The Genetic Code
G. Protein structure and composition
1. Proteins: made of one or more
polypeptides which are sequences of amino
acids held together by peptide bonds
2. 20 different amino acids arrange in a
particular sequence make up the proteins
3. Sequence of amino acids determines how the protein
will twist and fold into its shape
4. Function depends on its ability
to bind with other molecules
5. The function depends on its shape, the shape depends
on the sequence of amino acids which is determined
by the genetic information
H. Translation: process of assembling proteins from
information encoded in mRNA
1. mRNA moves to ribosome where protein synthesis
will take place
2. Amino acid are floating in the
cytoplasm and tRNA picks them
up and takes them to the ribosomes
3. tRNA: top section bonds to amino acid and the
bottom section has three nucleotides called an
anticodon
a) anticodon: complementary to the mRNA
codon that it will pair up with
b) pairing of the anticodon with the codon
ensures that the amino acids are added to the
growing protein in the correct order
c) same base pairing rules:
anticodon is AAA then
codon is UUU
4. Ribosomes: made of proteins and rRNA and
have three binding sites for translation
a) one site holds mRNA
b) two other sites hold the tRNA whose
anticodons will pair with the mRNA
5. Ribosome attaches to the start codon (AUG) on
the mRNA
6. tRNA with the anticodon UAC brings in the
amino acid and links to the mRNA
7. Ribosome moves 3 nucleotides along the mRNA
strand and next tRNA binds to the codon bringing
the correct amino acid
8. The two amino acids brought in and form a
peptide bond
9. The process of moving the ribosome, binding the
tRNA and forming a bond between the next amino
acids continues until a stop codon is reached
10. mRNA is released from the ribosome and the
protein is complete
Translation
Section 12-3
Nucleus
Messenger RNA
Messenger RNA is transcribed in the nucleus.
Phenylalanine
tRNA
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.
Ribosome
Go to
Section:
mRNA
Transfer RNA
Methionine
mRNA
Lysine
Start codon
Translation (continued)
Section 12-3
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.
Lysine
Growing polypeptide chain
Ribosome
tRNA
tRNA
mRNA
Completing the Polypeptide
mRNA
Ribosome
Go to
Section:
Translation direction
The process continues until the ribosome reaches
one of the three stop codons. The result is a
growing polypeptide chain.
Translation
Translate and Transcribe
You Tube
I.
Human Genome
1. Human genome: the complete gene sequence
2. 3.2 billion base pairs in the 23 human
chromosomes
3. Now scientists need to understand what the
DNA sequences encode
4. Bioinformatics: used computers to compare
different DNA sequences
5. Will help to diagnose, treat, and prevent genetic
disorders, cancer and infectious diseases in the
future. Genome animations