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Chapter 12
Making Proteins
Differences between RNA and DNA
• DNA = double strand; RNA = single strand
• RNA contains Ribose instead of
deoxyribose.
• RNA uses a nitrogen base called Uracil
instead of Thymine.
• What would the conjugate strand of RNA
be for the following DNA sequence?
AAGCATTCAT
From Genes to Proteins
• All the proteins in your body need to be
produced.
• Transcription – The stage of protein
synthesis in which the information in DNA
for making a protein is transferred to an
RNA molecule.
• A DNA molecule is copied into a molecule
called RNA (Ribonucleic Acid) A single
stranded nucleic acid.
Transcription
• Occurs in the Nucleus
• RNA polymerase binds to a spot on DNA
that codes for a specific gene. RNA
polymerase is an enzyme that builds a
strand of RNA from DNA.
• RNA polymerase unwinds & opens the
DNA exposing the nucleotides.
• RNA polymerase reads the DNA and links
the complementary nucleotides together.
Now that RNA is made…
• After the copy of DNA is made the genes
that are encoded in the RNA are read in
order to piece together the protein.
• Translation – The stage of gene
expression in which the information in
RNA is used to make a protein.
• Gene Expression – Combination of
Transcription & Translation. AKA Protein
Synthesis.
Translation
• Occurs in the Cytoplasm
• RNA is read three Nitrogen bases at a time
by a molecule to code for one amino acid.
• The three-nucleotide sequence of RNA is
called a codon.
• Each 3-nucleotide codon codes for a
specific amino acid.
• A codon chart is used to find what amino
acid each codon codes for.
RNA Used in Making a Protein
• There are three RNA molecules that are
involved in the production of proteins.
• Messenger (mRNA)
• Ribosomal (rRNA)
• Transfer (tRNA)
• Each one of these molecules has a
specific function in protein synthesis.
Translation
• mRNA carries the RNA copy out of the
nucleus and into the cytoplasm.
• The mRNA takes the RNA to a ribosome
which will build the protein.
• A tRNA molecule brings amino acids to
the ribososme.