Transcript The Wonderful World of DNA

The Wonderful World of
DNA
(Deoxyribonucleic Acid)
Review
Everything is made of matter
 Matter is made of molecules
 Molecules are made from elements
 DNA is a molecule that is made from other
molecules
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What does it look like
DNA Fun Facts
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DNA was first isolated in 1869 by Friedrich
Miescher.
James Watson and Francis Crick figured out the
structure of DNA in 1953. Although they did
“borrow” much of the research to figure it out.
DNA is a double helix.
One chromosome can have as little as 50 million
base pairs or as much as 250 million base pairs.
If unwound and tied together, the strands of DNA
in one cell would stretch almost six feet but would
be only 50 trillionths of an inch wide.
Over 99% of our DNA sequence is the same as
other humans’
DNA is important because
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It has a really long, scientific
name
It is the instructions that
code for the creation and
maintenance of living things
It is what mitosis uses for its
phases
All of the above makes DNA
important
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A double helix is like a
Spiral Staircase
A twisted ladder
A piece of licorice
More than one of the
above are correct
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The DNA model
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It all starts with the “backbone”
A Phosphate is connected to the deoxyribose
sugar
 The bonds holding them together are
STRONG.
 We don’t want the DNA to separate along
backbone
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The DNA model
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The building block is a nucleotide
DNA is built from small similar parts called
nucleotides
 It consists of three parts:
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 A phosphate
 Connected
to the Sugar
 A nitrogen base connected to the sugar
There are 4 nitrogen bases: Adenine,
Thymine, Guanine and Cytosine
 They pair up on opposite sides of the DNA
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 Adenine
with Thymine & Cytosine with Guanine
DNA has two backbones.
True
False
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Nitrogen bases in DNA pair up like
this:
A – C, G - T
G – A, T - G
A – T, G - C
They don’t pair up at all
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A nucleotide is like
A lego
A brick
A puzzle piece
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A little video clip showing this DNA Stuff
The Code
The A, T, G & C’s are set in an order for a
specific trait
 The code can only be read when the DNA
is open
 It is coded in 3 letter sequences.
 Each 3 letter sequence is called a
CODON.
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Which would be an example of a
codon?
CBA
GATTACA
KFAN
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Reading the Code
When DNA is read, it is read one gene at a
time
 Each gene codes for a specific trait
 When a gene is ready to be read, DNA
unzips
 A molecule called mRNA is formed as a
copy of the code
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mRNA
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mRNA (messenger RNA)
Made with Ribose sugar instead of
Deoxyribose
 Only a single strand, but still twisted
 Uses Uracil as a nitrogen base instead of
Thymine
 Built as a match to DNA
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Reading the code
Each codon is represented by one AMINO
ACID.
 Amino Acids are assembled in the order of
the code.
 When assembled they are called
PROTEINS.
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We still haven’t said how the code
is read!?
The actual reading is done by the
RIBOSOMES outside of the nucleus.
 They call for molecules call tRNA that
carry specific amino acids
 The tRNA’s bring in the aminos and attach
them to the ones that are there, creating a
long line of amino acids call a PROTEIN.
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tRNA
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tRNA (transfer RNA)
Is a short strand of RNA
 Only 3 nucleotides long (1 codon)
 Carry one specific amino acid that is specific
to the code that it has
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The Process is in Two Stages
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Stage 1 (Transcription)
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DNA unzips
mRNA is made
mRNA is released into nucleus
DNA zips back up
What is created in the end of
transcription?
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2nd half of DNA
tRNA
Unzipped DNA
mRNA
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Transcription Video
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Stage 2 (Translation)
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mRNA goes out of the nucleus
Attaches to a ribosome at one codon
Ribosomes read the code and call for one of the
tRNAs with the opposite code
tRNA matches up with the mRNA at the ribosome,
attaches its amino acid to the others that are there
(peptide bond between aminos), then leaves
Continues to do this until the mRNA runs out
mRNA returns to the nucleus and breaks up into its
nucleotides.
The amino acid chain is the PROTEIN (or a
polypeptide) and is released to control the trait
What is created in the end of
translation?
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Protein
tRNA
Unzipped DNA
mRNA
None of the above
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Translation Video
Amino Acid Table