Integrated
Science
Ch. 12
Molecular
Genetics
I. DNA:
A. The Genetic Code
- a universal
language of cells
James Watson & Francis Crick
- discovered the structure of DNA in 1953
X-ray
Diffraction
of DNA
Rosalind
Franklin
(died of cancer
in 1958)
B.DNA Structure
1.3 Main Parts
a) Sugar
(Deoxyribose)
b) Phosphate
c) Bases
C. Bases
(1) Adenine (A)
Guanine (G)
(2) Cytosine (C)
Thymine (T)
The Watson-Crick Model
of DNA Structure
2. Nucleotide:
- a subunit of a
nucleic acid
containing
a sugar,
a phosphate,
and a base
3. Shape:
- double helix
a) backbone - sugars
and phosphates
b) paired bases form
on the inside
c) Base Pairing Rule:
A:T, C:G
D. DNA Replication:
- process by which DNA makes an
exact copy of itself
Free
Nucleotides
DNA
Replication
New
double
helix with
1 old &
1 new
strand
Parental
DNA
double
helix
II. RNA:
- Nucleic acid
that makes
protein
- Made of RNA
nucleotides
A. RNA Structure
- Comparison of DNA and RNA
Shape
Sugar
Base
Size
Location
Function
DNA
double helix
deoxyribose
thymine
very large
nucleus
- stores genetic
info
- replication
- makes RNA
RNA
single helix
ribose
uracil
smaller
cytoplasm
- makes
protein
B. Transcription:
- process by
which DNA
makes a copy
of RNA
DNA base
half
Original DNA
transcribes
RNA
pairs separate
Transcription: First Two Steps
Transcription: Last Step
Three Types of RNA
mRNA
A G A U G C G A G U U A U G G
codons
Ribosome
contains rRNA
Met Amino
acid
tRNA
anticodon
Large
subunit
1 2
Small
subunit
tRNA
docking
sites
UGA
C. Messenger RNA (mRNA):
- carries the information for
making a protein from DNA
to the ribosomes
- acts as a template (pattern)
- contains codons:
triplets of bases that code
for a particular amino acid
- Start Codon:
(AUG) - marks the start of a protein
- Stop Codon:
(UAA, UAG, UGA) - marks the end
Information Flow:
DNA
RNA
Protein
D.Transfer RNA (tRNA):
- transfers amino acids from the
cytoplasm to the mRNA
E. Ribosomal RNA (rRNA):
- ribosomes are made of rRNA and
protein
- ribosomes ‘read’ mRNA amd join
together amino acids to make
proteins
III. Translation:
- decoding the "message" of
mRNA into a protein
Translation: Initiation
Translation: Elongation 1
Translation: Elongation 2
Translation: Elongation 3
Translation: Elongation 4
Translation: Elongation 5
Translation: Termination
III. Mutations
- any change in the nucleotide
sequence of DNA
- can occur in any cell
* Somatic (body cell) Mutations:
- may be harmful but not inherited
* Gamete (germ cell) Mutations:
- can be inherited
III. Mutations
- usually recessive
- many are harmful
- some are neutral
- some beneficial
(leads to evolution)
- Mutagens: cause mutations
1) Radiation- UV, X-rays, etc.
2) Chemicals (asbestos, etc.)
A. Types of Mutations:
1. Point Mutation
- change of a single base
- ex: sickle-cell anemia
AUG GGG CUU CUU AAU
AUG GGG CAU CUU AAU
Normal Red Blood Cells
Sickled Cells
Link to a Video
Clip about Sickle
Cell Disease(0:59)
2. Frameshift Mutation
- addition or deletion of a single base
AUG GGG CUU CUU AAU
AUG GGG CAU UCU UAA U
The End