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The Genetic Code
and Protein Synthesis
Genes and the Genetic Code

Gene: a segment of DNA on a
chromosomes that codes for a specific trait

Genetic Code: formed by the order of
nitrogen bases along a gene that specifies
what type of protein will be produced
How cells make proteins

A cell uses the coded information from a
segment of DNA (gene) to make a specific
protein

Why make proteins?
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Proteins determine your traits, hair color, eye
color, tongue rolling ability, etc.

Things that are not traits: athletic ability
What Protein Synthesis involves:
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DNA found in the nucleus
Ribosome: where the proteins are made
RNA (see below)
Amino acids: these are the building blocks
of proteins
RNA


Similar to DNA
Structure of RNA:
1.
2.
3.
4.
Sugar is different
Single-stranded
Uracil replaces thymine
Still has cytosine (C), guanine (G), and adenine
(A)
Draw me under
DNA
Draw me
under RNA
2 Types of RNA
1.
mRNA: messenger RNA
–
2.
Copies the coded message from the DNA in the
nucleus and carries the message to the ribosome in
the cytoplasm
tRNA: transfer RNA
–
Picks up and transfers amino acids in the cytoplasm
to the ribosome and adds them to the growing
proteins
DNA
RNA
The Steps of Protein Synthesis
1.
In the nucleus, DNA serves as a pattern for
making mRNA
2.
The DNA molecule unzips and RNA bases
match up along one strand of the DNA.


This transfers the information from the DNA to
the mRNA strand
Each group of 3 bases on the mRNA codes for
one amino acid
Section 12-3
Steps 1 and 2
Adenine (DNA and RNA)
Cystosine (DNA and RNA)
Guanine(DNA and RNA)
Thymine (DNA only)
Uracil (RNA only)
RNA
polymerase
RNA
DNA
3.
The mRNA moves out of the nucleus and
attaches to the ribosome, where protein
chain production begins
4.
tRNA attaches to the mRNA, and reads the
mRNA code
5.
If the tRNA matches the code on the
mRNA, it drops off its amino acid
6.
The amino acids are joined to make a
protein

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