DNA AND PROTEIN SYSNTHESIS
DNA
PROTEIN
What structures are found in the
nucleus?
What is a gene?
• Gene: a portion of DNA that contains
the codes (instructions) for one protein.
GENE
• A gene is a sequence
of nucleotides that
has the code
(instructions) for
making a specific
protein
• The average gene is
3000 bases
• Total number of
genes is 30,000 to
35,000
Protein Synthesis
The building of proteins from amino
acids
• Why are proteins important?
– Make up important structures like muscles and
cell membranes.
– Substances like enzymes, antibodies and
hormones are made of proteins
– Traits like hair and eye color are the results of
proteins
RIBOSOME
Where is DNA?
Where are proteins made?
ribosome
• Where are
proteins
synthesized ?
By the ribosomes
In the cytoplasm.
• What are proteins
made of?
– Proteins are long
chains of amino
acids
– There are 20
different amino
acids
• The instructions
for making
proteins
(the order of the
amino acids in a
particular protein)
are encoded in
the DNA
(the code)
CODON
• Codon – a set of
three nitrogenous
bases that
represents an amino
acid
Codon
• The bases are arranged in threes called
codons.
AGG-CTC-AAG-TCC-TAG
TCC-GAG-TTC-AGG-ATC
Protein Synthesis takes
place in 2 stages
transcription
translation
• RNA
RNA
– Ribonucleic acid
– RNA is similar to
DNA but is single
stranded
– RNA contains the
sugar ribose (not
deoxyribose)
– The nitrogen base
uracil replaces
thymine
Three Types of RNA
• Messenger RNA
(mRNA)
– Is formed in the
nucleus
– Carries the
instructions from the
DNA in the nucleus
to the ribosomes in
the cytoplasm
–“The Messenger”
CODON
• Order of nitrogen
bases in mRNA that
determines the type
and order of amino
acids in a protein
• mRNA has the
CODON!
• There are 64 possible codons, but only 20
amino acids to code for
TRANSFER RNA
• Transfer RNA (tRNA)
– Carries amino acids
from the cytoplasm
to the ribosome.
–Has the
anticodon
– “The Worker”
RIBOSOMAL RNA (rRNA)
– The ribosome is made of rRNA.
Transcription
• During the production
of proteins the
“blueprints”
(instructions) are
located in the nucleus,
in a code in the DNA
• DNA acts as a template
for making messenger
RNA
Complementary base pairing
DNA Base
Complementary RNA
Base
G
C
C
G
A
U
T
A
Transcription
• mRna picks up the
triplet code from
the DNA
• m RNA leaves the
nucleus.
•The instructions (codon) are
then carried to the cytoplasm
• A ribosome attaches to
the mRNA.
• The instructions carried
by the mRNA will be
used to assemble the
amino acids in the
proper order
Translation
• The amino acids are
brought to the
ribosomes by the tRNA
molecules to be
assembled into a
protein (translation)
• The order of the amino
acids is determined by
the codon on the
mRNA
Protein Synthesis
• The tRNA
anticodon pairs
with the mRNA
codon
• The tRNA
releases the
amino acid which
bonds to the
other AA ‘s
forming
a chain = protein
MUTATIONS
Mutations
• If DNA is not copied exactly, proteins
made from its instructions could be
made INCORRECTLY
• Mutation: any permanent change in
the DNA sequence in a gene or
chromosome.
• Factors that cause mutations: X rays,
sunlight, and some chemicals
Results of a Mutation
• Genes control the traits you inherit.
• Without correctly
coded proteins, an
organism can’t
grow, repair, or
maintain itself.
• A change in a gene
or chromosome can
change the traits of
an organism.
Results of a Mutation
• If the mutation occurs in a body
cell, it might not be life threatening
to the organism.
• If a mutation occurs in a sex cell, then
all the cells that are formed from that
sex cell will have that mutation.
Results of a Mutation
• Many mutations are harmful to
organisms, often causing their
death.
• Some mutations do not have any
effect on the organism.
•Some mutations can be helpful and
give the organism a better chance of
surviving.
DNA and Mutations –
Lets looks at different mutations
THE DOG BIT THE CAT
Mutations - Substitution
THE DOG BIT THE CAT
•
Substitution - Replace just one letter:
THE DOG BIT THE CAR
Deletion
THE DOG BIT THE CAT
•
Deletion: Delete just one letter (T):
THE DOG BIT HEC AT
Insertions
THE DOG BIT THE CAT
• Insertion
- Add just one letter (E):
THE DOE GBI TTH ECA T
Cells have “proof reading” proteins that
constantly check the DNA and fix errors, so most
are corrected