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Replication
Transcription
Translation
DNA
1. Double Stranded Helix
2. Hydrogen Bonds between
Nitrogenous Base Pairs
3. Adenine-Thymine and
Guanine-Cytosine
Replication
• The duplication of DNA which occurs
during the S phase of Interphase.
• 1 Strand  2 Complementary Strands
• DNA Polymerase
Hydrogen bond
(H-bonds)
thymine
adenine
cytosine
guanine
phosphate
deoxyribose sugar
Sugar / phosphate “strand”
Nitrogenous base “rung”
DNA nucleotide
Deoxyribose sugar
phosphate
RNA nucleotide
ribose sugar
Nitrogenous base
(guanine)
phosphate
Nitrogenous base
(uracil)
Step 1: Hydrogen bonds
between complimentary
bases break
DNA “unzips”
Step 2: DNA strands
pull apart from each other
Step 3: DNA nucleotides in the cell
match up with each side of the
“unzipped” DNA
each “unzipped’ strands forms a
template for a new strand
Step 4: Each “old’ strand
forms a template for a
“new” strand
two identical DNA
molecules form
“new” strand, identical
sequence to the original
“old” (original) strand
Transcription
• The process by which a molecule of DNA is
copied into a complementary strand of
RNA.
• 1 Strand DNA  2 Strands RNA
• RNA Polymerase
• Semiconservative
• Difference between
• replication and
• transcription
DNA
RNA
Step 1: Hydrogen bonds
between complimentary
bases break
DNA “unzips”
Step 2: DNA strands
pull apart from each other
Step 3:
RNA nucleotides
in the cell match
up with only one
side of the
“unzipped” DNA
each “unzipped’
strands forms a
template for a
mRNA strand
RNA nucleotide
Step 4:
RNA nucleotides
continue to match
up with
“unzipped” DNA
until the message
is completely
transcribed
mRNA strand
One side of DNA strand
mRNA strand
Step 4:
mRNA strand
breaks off
from the DNA
strand
One side of DNA strand
Step 5:
mRNA strand
leaves the
nucleus for
the ribosome
Step 6: Once the mRNA
leaves, the DNA “zips”
back together
Where rep, transl, transc occur
Translation
• The process in which the information in the
nucleotide base sequence of mRNA is used to
dictate the amino acid sequence of a protein.
• 1 Strand RNA  Amino Acid Chain  Protein
The problem: How does a
particular sequence of
nucleotides specify a particular
sequence of amino acids?
By means of transfer RNA
molecules, each specific for one
amino acid and for a particular
triplet of nucleotides in mRNA
called a codon. The family of
tRNA molecules enables the
codons in a mRNA molecule to
be translated into the sequence
of amino acids in the protein.
RNA and Protein Synthesis
• RNA is a Single
Stranded Nucleic Acid
• RNA Acts as a
Messenger between
DNA and Ribosomes
• Process Takes Amino
Acids and Forms
Proteins
Why Is It Necessary?
• DNA / Nucleus
• Ribosomes / Cytoplasm
• Need a Messenger
Definitions
• Codon
1. Three-base segment of mRNA that
specify amino acids.
2. Sense Codons
3. Nonsense Codons
• Anticodon
1. Three-base segment of tRNA that
dock with a codon.
2. Docking results in deposition of amino acid.
Protein Synthesis
• Proteins are coded directly from the mRNA
with 3 bases (one codon) for each amino
acid. What’s up with that?
Mutation
• A change in the nitrogenous base sequence
of DNA; that change causes a change in the
product coded for by the mutated gene.
Mutations
What happens when you get insertions or deletions of bases in
the DNA sequence?
Usually you end up with a mess.
THE BIG FAT CAT ATE THE RAT AND GOT ILL
Deletion of one base
THE IGF ATC ATA TET HER ATA NDG OTI LL
And its all pops and buzzes.
Sickle-Cell
Anemia
Definitions
• Carcinogens
Substances and preparations which, if they are
inhaled or ingested or if they penetrate the skin;
may induce cancer or increase its incidence and
can affect any cells or tissues
• Mutagens
may induce hereditary genetic defects or increase
their incidence and effect the germ cells (gonads)
• Teratogens
may induce non-hereditary congenital
malformations or increase their incidence and
effect the growing fetus
Mutagens
•
•
•
•
•
•
•
Tobacco products
Nitrous Acid
Mold Toxins
X-rays
Gamma Rays
UV Radiation
Some Artificial Sweeteners