Download (Microsoft PowerPoint - Biology \226 DNA Protein Synthesis and

Biology – DNA
Protein Synthesis and
Fingerprinting
Spring 2009
Proteins - Review
• Chains of amino
acids
• 20 named types
• Create/build
structure within
organisms
• Function as
important
biochemicals
• Ex: hair, skin,
tissues in
organs, muscle,
enzymes
• Symbolize amino acids as shapes
• Ex:
Valine
Alanine
Tyrosine
Etc………………….
Phenylalanine
Protein Synthesis
• Process by which proteins are
built in cells
• DNA has code for building the
protein, ie. the amino acid
sequence
• Code?
• Sequence of nitrogen bases
• Problem, where are proteins
built?
• Ribosomes in cytoplasm
• DNA “stuck” in nucleus
• Who can help DNA?
• RNA can travel between nucleus
and cytoplasm
RNA Review
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DNA sugar?
Deoxyribose
RNA sugar?
Ribose
DNA bases?
Adenine, cytosine, guanine and thymine
Base pairing?
A-T and C-G
RNA bases?
Adenine, cytosine, guanine and uracil
Base pairing?
A-U and C-G
DNA shape?
Double helix
RNA shape?
Often single stranded; sometimes a weird cloverleaf shape that is partially
double stranded
Protein Synthesis
• Goal: to make a
piece of dark hair
protein according to
DNA base code
(gene) on
a chromosome in
nucleus
• Must assemble
amino acids in
correct order
Assume this is the
correct sequence of
amino acids
Step One
• Begins in
nucleus
• Strand of
DNA (gene)
for dark hair
• Complementary
bases?
Step Two
• DNA uncoils
• DNA unzips
• Remind you of
another process?
• NOT DNA
duplication this
time
Problem?
• DNA (chromosome) is in nucleus
• Amino acids (proteins) are assembled in
the cytoplasm at the ribosome
• RNA to the rescue!!
Step Three
• Floating in the
nucleus are
“spare part”
RNA nucleotides
made by the
nucleolus
Step Four
• “Spare Part “
RNA nucleotides
move in
• Pair up with
unzipped DNA on
one side
• Bond to form a
strand of RNA
Step Five
• RNA strand now has
the DNA code for
dark hair
• Detaches and leaves
the nucleus
• Travels to cytoplasm
and ribosome
• Called: messenger
RNA (mRNA)
• DNA zips up and coils
up
In cytoplasm
• Steps of the process occurring in nucleus
are called: Transcription = DNA
passes the code to RNA
• Once mRNA moves into cytoplasm, a
second phase called translation begins
• Translation = mRNA translates the code
into a specific amino acid sequence
(protein)
Step Six
• Floating in the cytoplasm is
another type of RNA
• Cloverleaf shaped with some
bases bonded
• 3 “free” bases on one end
• Opposite ends holds a
specific amino acid
• Act like “semi trucks”
• “Haul” amino acids to the
protein factory
• Called: transfer RNA (tRNA)
Called: Triplet code
Three bases code for one
specific amino acid
Each amino acid has its own
specific code
Some have more than one
Ex: phenylalanine code can
be: AAA or AAG
Having 4 different nucleotide
bases and having 3 bases
code for one amino acid,
allows for how many different
combinations?
Would two bases be enough
to code for 20 different amino
acids?
tRNA
Step Six Continued
• tRNA haul their
amino acids to
ribosome
• How do they know
where to drop their
load?
• Pair up with bases
on mRNA
• Sequence of 3 base
pairs on mRNA is
called a codon
• Opposite sequence
of 3 on tRNA is
called an
anticodon
Step Seven
• Amino acids are so
close, they bond in a
chain to form a specific
protein
• In this case, dark hair
protein
• Protein is released into
the cell
• tRNA release from
mRNA and travel back
into cytoplasm to pick up
another “load” (amino
acid)
Mutations
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Mutation = mistake in DNA base sequence
Often harmful, sometimes positive
Ex: rabbit with white coat
Mutagen = agent/substance that can cause
mutations
• Ex: ultraviolet radiation – sunlight,
nuclear radiation, chemicals in food,
air, water – cigarette smoke, asbestos
drugs
Mutation – Impact on Protein
Synthesis
Mutated Gene
• Assume the
original DNA
sequence is
mutated in a
gene that codes
for an important
protein to clot
blood
Normal Gene
Mutated DNA gene unzips
What type of mRNA will be built?
Normal gene mRNA
Mutant Gene mRNA
Normal Gene Translation at the
Ribosome
Mutated Gene Translation at the
Ribosome
Mutated Translation Continued
Normal Blood Clotting Protein
Mutated Blood Clotting Protein