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DNA and Protein Synthesis
Chapter 5
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DNA – a molecule that stores your information
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Amino acid chains make up a protein molecule.
+ Facts
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There are 20 different amino acids
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Each composed of 3 nucleotides
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They combine to make thousands of different proteins
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DNA stores the info that enables cell to put together the correct
sequence of amino acids!
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DNA
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Doubled stranded spiral
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Twisted Ladder
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Four nucleotides in DNA:
Adenine (A)
■ Thymine (T)
■ Cytosine (C)
■ Guanine (G)
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3 nucleotides = codon
needed to make one of the 20 amino acids
code
Some amino acids
have multiple triplet
codes:
Ex: Val has →
GUU
GUC
GUA
GUG
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QUESTION: What amino acid does CAC code for?
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Start Codon:
Stop Codons:
● AUG
UGA
● Also codes for the
amino acid Methionine
UAA, UAG,
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Practice!
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A gene is…
■ The
entire sequence of bases that codes
for all the amino acids in a protein.
■ Each
is made up of a sequence of bases
at a particular location on the DNA
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DO NOW:
Why do our bodies need proteins?
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Types of Proteins
1. Structural functions in support, examples: elastin, collagen, and keratin
2. Storage food source, examples: ovalbumin and casein
3. Transport moves other substances, examples: hemoglobin and cell membrane proteins
4. Hormonal coordinates bodily activities, example insulin
5. Contractile movement, examples: actin and myosin
6. Antibodies defense, examples: Ig.E, IgA, and Ig.G
7. Enzymes aid in chemical reactions, examples: amylase and proteases
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3 Steps to making a Protein, known as the
CENTRAL DOGMA
1.
DNA Replication (DNA to DNA)
2.
Transcription (DNA to RNA)
3.
Translation (RNA to protein)
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DNA Replication
Replication: Before a cell divides, all of the DNA is copied.
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Process:
■ Two strands of DNA unwind (like twizzlers)
■ Nucleotides (A-T & G-C) pair up with each of the strands
■ Now there are two identical DNA molecules
■ Each molecule has a strand of old and new DNA
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Original DNA strand on each used
as a template!
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Transcription (DNA to RNA)
■ When
using DNA to make a protein, RNA
(ribonucleic acid) carries the information from
DNA to a ribosome (where a protein is formed)
■3
types of RNA used when making a protein:
■ Messenger RNA = mRNA
■ Ribosomal RNA = rRNA
■ Transfer RNA = tRNA
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Transcription
STEPS:
1.The DNA molecule opens up along a gene
2.RNA nucleotides match up and join the open DNA
strand
3.The completed RNA strand is released and moves to
the cytoplasm.
1. Many copies of RNA can be made from that DNA
strand
4.That DNA strand then closes up when transcription is
done
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DNA vs. RNA Base Pairs
DNA
RNA
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Adenine-Thymine
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Adenine-Uracil
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Cytosine-Guanine
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Cytosine-Guanine
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DNA to RNA Practice!
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Translation (RNA → PROTEIN!)
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Takes place in the ribosome and cytoplasm
1.
A ribosome attaches to an mRNA molecule at the beginning of a coding
region (start codon)
2.
tRNA matches up and joins the mRNA strand
3.
As the ribosome moves along the mRNA strand, it attaches the amino acids
to another.
4.
tRNA leaves once it “drops off” the matching amino acid
5.
Once the ribosome reaches the “stop codon”, the chain is complete and a
protein is made!
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The Central Dogma - Video
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DO NOW: Name the steps of protein synthesis and the
locations at which they occur.
1.
location:
2.
location:
3.
location:
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Protein Synthesis Recap
1.
DNA replication (DNA TO DNA TO DNA)
2.
Transcription (DNA TO RNA)
3.
Translation (RNA TO PROTEIN)
WHY IS THIS SO IMPORTANT?