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Biology
Biology
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12–3 RNA and Protein Synthesis
12-3 RNA and Protein Synthesis
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12–3 RNA and Protein Synthesis
12–3 RNA and Protein
Synthesis
Genes are coded DNA instructions that control the
production of proteins.
Genetic messages can be decoded by copying part
of the nucleotide sequence from DNA into RNA.
RNA contains coded information for making proteins.
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12–3 RNA and Protein Synthesis
The Structure of RNA
The Structure of RNA
There are three main differences between RNA and DNA:
•The sugar in RNA is ribose instead of deoxyribose.
•RNA is generally single-stranded.
•RNA contains uracil in place of thymine.
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12–3 RNA and Protein Synthesis
Types of RNA
Types of RNA
There are three main types of RNA:
• messenger RNA
• ribosomal RNA
• transfer RNA
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12–3 RNA and Protein Synthesis
Types of RNA
Messenger RNA (mRNA) carries copies of
instructions for assembling amino acids into proteins.
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12–3 RNA and Protein Synthesis
Types of RNA
Ribosome
Ribosomal RNA
Ribosomes are made up of proteins and ribosomal
RNA (rRNA).
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12–3 RNA and Protein Synthesis
Types of RNA
Amino acid
Transfer RNA
During protein construction, transfer RNA (tRNA)
transfers each amino acid to the ribosome.
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12–3 RNA and Protein Synthesis
Protein Synthesis
DNA
molecule
DNA strand
(template)
5
3
TRANSCRIPTION
mRNA
5
3
Codon
TRANSLATION
Protein
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Amino acid
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12–3 RNA and Protein Synthesis
Transcription
Transcription
DNA is copied in the form of RNA
This first process is called transcription.
The process begins at a section of DNA called a
promoter.
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12–3 RNA and Protein Synthesis
Transcription
RNA
RNA polymerase
DNA
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12–3 RNA and Protein Synthesis
RNA Editing
RNA Editing
Some DNA within a gene is not needed to produce
a protein. These areas are called introns.
The DNA sequences that code for proteins are
called exons.
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12–3 RNA and Protein Synthesis
The introns are cut
out of RNA molecules.
RNA Editing
Exon Intron
The exons are the
spliced together to
form mRNA.
DNA
Pre-mRNA
mRNA
Cap
Tail
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12–3 RNA and Protein Synthesis
The Genetic Code
The Genetic Code
The genetic code is the “language” of mRNA
instructions.
The code is written using four “letters” (the bases:
A, U, C, and G).
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12–3 RNA and Protein Synthesis
The Genetic Code
A codon consists of three consecutive nucleotides
on mRNA that specify a particular amino acid.
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12–3 RNA and Protein Synthesis
The Genetic Code
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12–3 RNA and Protein Synthesis
Translation
Translation
Translation is the decoding of an mRNA
message into a polypeptide chain (protein).
Translation takes place on ribosomes.
During translation, the cell uses
information from messenger RNA to
produce proteins.
Nucleus
mRNA
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12–3 RNA and Protein Synthesis
Translation
The ribosome binds new tRNA molecules and amino
acids as it moves along the mRNA.
Phenylalanine
tRNA
Lysine
Methionine
Ribosome
mRNA
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Start codon
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12–3 RNA and Protein Synthesis
Translation
Protein Synthesis
Lysine
tRNA
Translation direction
mRNA
Ribosome
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12–3 RNA and Protein Synthesis
Translation
The process continues until the ribosome reaches
a stop codon.
Polypeptide
Ribosome
tRNA
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mRNA
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12–3 RNA and Protein Synthesis
Codon
Genes and Proteins
Codon Codon
DNA
Single strand of DNA
Codon Codon Codon
mRNA
mRNA
Protein
Alanine Arginine Leucine
Amino acids within
a polypeptide
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12–3
Click to Launch:
Continue to:
- or -
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The role of a master plan in a building is similar
to the role of which molecule?
a. messenger RNA
b. DNA
c. transfer RNA
d. ribosomal RNA
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A base that is present in RNA but NOT in DNA is
a. thymine.
b. uracil.
c. cytosine.
d. adenine.
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The nucleic acid responsible for bringing
individual amino acids to the ribosome is
a. transfer RNA.
b. DNA.
c. messenger RNA.
d. ribosomal RNA.
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A region of a DNA molecule that indicates to an
enzyme where to bind to make RNA is the
a. intron.
b. exon.
c. promoter.
d. codon.
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A codon typically carries sufficient information to
specify a(an)
a. single base pair in RNA.
b. single amino acid.
c. entire protein.
d. single base pair in DNA.
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