Download How is DNA*s Genetic Code Used to Make Proteins?

Protein Synthesis
DNA
RNA
Protein
How is the code in DNA Used to Make
Proteins?
Using RNA (Ribonucleic Acid)!
RNA is similar to DNA (they are
both nucleic acids, and both are
made up of nucleotides) but
RNA has 3 significant differences:
•It is Single stranded (instead of
double stranded like DNA)
•It has the sugar ribose (instead
of deoxyribose like DNA)
•It contains the base Uracil (U) instead of Thymine
3 Types of RNA
• mRNA is Messenger RNA – made from a
section of DNA (a gene) in the nucleus (carries
DNA’s “message”)
• tRNA is transfer RNA – responsible for
transferring amino acids to a ribosome to
make a protein in the
cytoplasm
• rRNA isRibosomal RNA –
makes up ribosomes
that help assemble
proteins
Transcription: an mRNA COPY of a DNA
section (gene) is made in the nucleus
DNA
mRNA
• Enzymes “unzip” a section of DNA
• Complementary RNA nucleotides pair with DNA nucleotides and
bond together (AUCG) to make a SINGLE strand of mRNA based on
the DNA code
• The mRNA strand breaks away from the DNA and takes the DNA
“message” from the nucleus to the cytoplasm
DNA
mRNA = Transcription
• Enzymes “read” the
DNA bases in a gene
and put together a
complementary,
single-stranded mRNA
molecule based on the
DNA code
Example:
DNA sequence:
TAC CCA TGC CTG
mRNA sequence: AUG GGU ACG GAC
Remember, NO THYMINE in RNA!
Translation: the code in mRNA is TRANSLATED
into a sequence of amino acids – a protein
•mRNA travels out of the nucleus to a ribosome in the cytoplasm
•The ribosome holds the mRNA in place
RNA
•tRNA brings amino acids to the ribosome
•The nucleotides on mRNA are divided into groups of 3 (“triplets”)
•Each set of 3 nucleotides on mRNA is called a CODON
•One codon is the “code” for one
amino acid
•Codons on mRNA match up with
anticodons on tRNA for specific
amino acids
•Each tRNA delivers one amino
acid
•The amino acids are attached
(bonded) together to make a
protein (they are attached together
based on the original sequence in
the DNA molecule that mRNA was made from!)
Protein
Codons and Anticodons
Codon - a group of 3
bases in mRNA (that
“code” for ONE amino
acid)
*There are 20
different amino acids
Anticodon – a group of 3 bases in tRNA (that
are complementary to a codon in mRNA)
“Decoding” the message – the Genetic Code (based
on codons in mRNA)
How do mRNA, tRNA and the ribosomes know which amino acids to put into the protein?
•THE GENETIC CODE!
Based on codons (triplets) in mRNA
Universal to ALL LIFE!!!
http://img.genciencia.com/2007/06/codigogenetico2.gif
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Transcription and Translation
http://www.youtube.com/watch?v=41_Ne5m
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The Protein
• Each protein is a chain of amino acids that has
a specific job
• The structure (shape) of the protein depends
on the sequence of amino acids and the
folding of the protein
Transcribe and Translate!
DNA: TAC ACT GGC TAA CGT TCC AGT ACC AAT GCG ATT
mRNA: ________________________________________
tRNA: _________________________________________
amino acids: _____________________________________
DNA: TAC ATC GTC TCG CCT AGT CCT GAA CTG CCA ACT
mRNA: _________________________________________
tRNA: __________________________________________
amino acids: _____________________________________
Mutations
• Mutation = a change in DNA (genetic material)
• Mutations can change ONE single base pair (point mutations) or
they can change long sequences of DNA/ chromosomes
• IF mutations occur in gametes, they can be passed on to offspring!
• IF the bases in DNA are changed, the mutation is copied into mRNA
during
transcription,
and then put
into the amino
acids/ protein
during
translation (this
usually means
the protein doesn’t “work” properly, if at all)
Mutations
Original DNA:
Original mRNA:
Original Amino Acids:
TAC CTT CAG GCG
AUG UGG GUC CGC
Met - Glu - Val - Arg
Mutated DNA:
Mutated mRNA:
Mutated Amino Acids:
TAC CAT CAG GCG
AUG UGA GUC CGC
Met – Val – Val - Arg
Example: Sickle cell anemia (CTT in DNA is
changed to CAT, changing one amino acid
in the protein)- red blood cells are sickleshaped instead of round and do not carry
oxygen as well
Label the Diagram
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Nucleus
DNA
mRNA
Transcription
cytoplasm
tRNA
Ribosome
Amino acid
Protein
Codon
anticodon
translation
Complete the Following Table
DNA
AAC TAG GGT Explain how DNA is transcribed.
Sequence
mRNA
codons
What does the ‘m’ mean in mRNA?
Explain why.
tRNA anticodons
Explain how the mRNA code is
translated into amino acids.
Amino
acid
sequence
Describe how a protein is formed
and identify 3 roles of proteins.