Download Chapter 10: Nucleic Acids

Chapter 10: Nucleic Acids
And Protein Synthesis
Essential Question: What roles do DNA and RNA play in storing genetic
information?
I.
DNA:
A.
Function
1.
DNA stores and transmits the genetic information that tells
cells which proteins to make
2.
B.
Structure of DNA
1.
Made of repeating units called nucleotides
a)
Sugar:
b)
Phosphate group
c)
2.
Four types of nitrogen bases
a) Adenine:
b) Guanine:
c) Cytosine:
d) Thymine:
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)
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C.
D.
E.
Double helix:
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
Complementary Base Pairing:
1.
Adenine pairs with
2.
Guanine pairs with
3.
Base sequence: order of nitrogenous bases on a chain of
DNA
4.
ACCTGTGAGAC
TGGACACTCTG
Replication of DNA:
1.
DNA unwinds
a)
replication fork:
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:
a)
Nucleotides are joined between the sugars and
phosphate groups
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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
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:
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.
II.
When replication is complete, two new exact copies of the
original DNA molecule are produced
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
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B.
RNA Function
1.
RNA carries the genetic information from the nucleus to the
cytoplasm
2.
C.
D.
E.
Structure of RNA
1.
Made of repeating nucleotides
2.
Sugar:
3.
Bases:
4.
Single strand
Types of RNA: each has a different function
1.
Messenger RNA (mRNA):
2.
Transfer RNA (tRNA): strand folded into a hairpin shape
that binds to specific amino acids
3.
Ribosomal RNA (rRNA):
Transcription:
1.
RNA polymerase: enzyme that makes RNA copies of
specific sequences of DNA
2.
Promoters:
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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:
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
F. Genetic Code:
1.
Codon:
2.
Several codons code for each amino acid
3.
Start codon:
4.
Stop codons: UAA, UAG, UGA: causes the ribosome to
stop translating
G. Protein structure and composition
1. Proteins:
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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.
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:
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
4.
a)
anticodon:
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:
Ribosomes:
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a)
one site holds mRNA
b) two other sites hold the tRNA whose anticodons will
pair with the mRNA
5.
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.
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.
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.
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