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Chapter 10: DNA, RNA,
and Protein Synthesis
Objectives:


Analyze and investigate emerging
scientific issues (e.g., genetically
modified food, stem cell research,
genetic research and cloning).
Describe advances in life sciences
that have important long-lasting
effects on science and society
(e.g., biological evolution, germ
theory, biotechnology and
discovering germs).
Analyze and investigate emerging scientific issues
(e.g., genetically modified food, stem cell
research, genetic research and cloning).
I. DNA Structure
A.
Double helix
A.
B.
Double twisted Ladder
Watson and Crick
A.
1953
II. DNA Nucleotides

Make up the long chains of the DNA Helix


Parts of the ladder
Consists of 3 parts:



Five carbon sugar (deoxyribose)
Phosphate group
Nitrogen base
III. Nitrogen bases


4 Nitrogen bases make up DNA
 T (thymine)
 A (Adenine)
 C (Cytosine)
 G (Guanine)
Base pairing rules
 Cytosine always pairs with Guanine
 Guanine always pairs with Cytosine
 Thymine always pairs with Adenine
 Adenine always pairs with Thymine
IV. Example

If you have the
sequence
A
T
C
G

It will be paired with

T
A
G
C
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V. DNA Replication


Process by which DNA is copied before a cell
divides
Steps:
Enzymes, called helicases, separate the DNA
strand
 Enzymes, called polymerase, add complimentary
bases pairs (T’s to A’s etc.)
 DNA polymerase fall off and there are 2 identical
strands

helicase
polmerase
-T
-A
-G
-C
-T
-A
-G
-G
ATCGATCC-
-T
-A
-G
-C
-T
-A
-G
-G
A–
T–
C–
G–
A–
T–
C–
C–
VI. DNA errors in
replication

Mutation
A change in the nucleotide
sequence
 Have serious effects on the
function of cells


Mutations that are not repaired are
called cancer
VII. Flow of Genetic Material

How does information from DNA get to
cell?
DNA – RNA - protein
 Transcription

 DNA

acts as a template for RNA synthesis
Translation
 Directs

assembly of proteins
Protein synthesis
 Forming
proteins bases on information
VIII. Protein Synthesis

Steps:


DNA double helix unwinds
Messenger RNA comes and copies






A (adenine) pairs with U (uracil)
Other bases pairs combine with usual complimentary
bases
RNA codes for codons, (3 base pair) see chart
Each codon is used to make an amino acids
Each amino acid combination makes proteins
Proteins control ALL functions of the cell!

The nearly universal genetic code identifies
the specific amino acids coded for by each
three-nucleotide mRNA codon.
Translation: Assembling Proteins
IX. The Human Genome


The entire gene sequence of the human
genome, the complete genetic content, is
now known.
To learn where and when human cells use
each of the proteins coded for in the
approximately 30,000 genes in the human
genome will take much more analysis.
10.4 Genetic Changes



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Mutation – any change in a gene or
chromosome.
*Leading cause of evolution.
Mutations that occur in gametes can be
inherited while mutations that occur in the
body cells are not passed to offspring. You
may have a genetic predisposition to the
defect.
Example Breast Cancer
A. Types of mutations



Point mutation – change in one base pair.
AAT, AAC.
( the amino acids are leucine,
still leucine) sometimes there is no effect on
the protein
Inversion – where two letters are switched.
Instead of AAT you could get ATA. (leucine
becomes tyrosine)
Frameshift – when an entire sequence is altered.
 Deletion shifts the frame left – ATATTC, delete the A
You get TATTC
-Insertion shifts the frame to the right – ATATTC, add a T you get TATATTC

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Insertion of a base or deletion of a base will
cause frameshift mutations. Could affect the
entire chromosome
Translocation – piece of chromosome
attaches to an entirely different
chromosome.
B. Causes of Mutations
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
Spontaneous – just happen, no
explanation
Mutagens – things that can cause
cancer. Such as: drugs, alcohol,
smoke, pollution, radiation (sun &
X-Ray, nuclear), chemicals
(dioxins, asbestos, benzene,
cyanide) and even high
temperatures.

Repairing DNA: Enzymes proof
read and correct nucleotides, but
the more mutations the more likely
a mistake will be missed and not
corrected. You need to limit your
exposure to mutagens to reduce
your risk of causing a mutation.