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DNA Notes
General Information
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The model was discovered by Watson &
Crick in 1953.
Stole lots of information from a female
scientist named Rosalind Franklin
They all ended up sharing the Nobel Prize
DNA (DeoxyriboNucleic Acid) makes up
genes.
Genes are sections of DNA that control one
trait.
Structure
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DNA is a double-stranded, helical molecule
It is composed of smaller parts (building
blocks) called nucleotides.
Each nucleotide is made of a phosphate, a
sugar (deoxyribose) and one of the 4 different
bases:
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Adenine
Thymine
Guanine
Cytosine
Structure (continued)
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DNA looks like a ladder that is twisted.
The sides of the ladder are the backbones of
the DNA. Each backbone of strong
phosphate & sugar bonds
The two strands are held together by weak
hydrogen bonds (like the rungs of a ladder)
Where is the molecule most likely to
separate? Why is this important?
When would this molecule split and copy?
The Genetic Code
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The bases in the middle of the DNA is the
code for the traits.
Every 3 bases (letters) code for one amino
acid. The 3 letter sequence is called the
CODON.
Amino acids make up a protein.
Proteins ultimately control what traits are
seen.
DNA Double Helix
Nucleotide
Hydrogen
bonds
Sugar-phosphate
backbone
Key
Adenine (A)
Thymine (T)
Cytosine (C)
Guanine (G)
Chromosome Structure
Chromosome
Nucleosome
DNA
double
helix
Coils
Supercoils
Histones
Review
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Why are genes important?
What are genes made out of?
How does DNA code for a trait (gene)?
Does DNA ever leave the Nucleus?
How do we read this code then?
Protein Synthesis
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SYNTHESIS = the making of something from
smaller parts
5 major players
2 major stages
The Players
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DNA
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Two Strands
Deoxyribose Sugar
Uses Thymine along with other bases
Always stays in the nucleus
Sets the order of amino acids that create proteins
The Players (continued)
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RNA (two types)
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RNA (RiboNucleic Acid)
Single Stranded
Ribose Sugar instead of deoxyribose sugar
Uses Uracil instead of Thymine
Created as a copy of a gene
Can be found inside the nucleus, as well as
outside
The Two Types of RNA
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mRNA (messenger RNA)
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assembled inside the nucleus, then moves into
the cytoplasm to the ribosomes
is an exact copy of one side of the DNA
is produced in transcription
produces protein during translation
Two Types of RNA (Continued)
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tRNA (transfer RNA)
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only found in cytoplasm
carries one specific amino acid with one specific
codon
carries the amino acid to the ribosome during
translation
after translation, it returns to the cytoplasm in
search of the same amino acid
Why RNA?
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DNA is way too valuable to leave the nucleus
and be left unprotected, in a harsh
environment
DNA is really big
More Players
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Protein
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A long string of amino acids, that are chemically
bonded
Controls the trait the gene is coding for
Ribosomes
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Manufactures the proteins that DNA codes for
Reads mRNA and calls for tRNA
The Two Stages
of Protein Synthesis
Transcription
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DNA unzips at the “GENE.” Forms a loop in
the DNA.
mRNA nucleotides match up with one of the
sides that is exposed. NOTICE, that the
mRNA that is being created is an exact copy
of one of the sides of DNA.
mRNA is built all the way to the end of the
gene. Then is released into the nucleus.
DNA then zips back up. This ends
transcription.
Translation
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mRNA leaves the nucleus.
mRNA attaches to a ribosome. What is a ribosome?
Ribosome attaches to one CODON. A CODON is …
Ribosome reads the CODON and calls for the tRNA that
has the opposite code.
tRNA comes and attaches to the ribosome. Checks to
make sure the code is OK. Drops off the AMINO ACID
onto the ribosome.
The ribosome then moves up to the next CODON. And
does the same thing over and over until it reaches the end
of the mRNA forming a string of AMINO ACIDS that is a
PROTEIN.
Protein is released into the cytoplasm to control the trait
the gene is being made for.
mRNA returns to the nucleus and breaks back up into
pieces.
Protein Synthesis Mastery
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Just like the Mitosis Mastery
Equal to 40 points, must get a 36 to pass or
you must retake
You can have a partner, but you must stick
with them pass or fail. Each of you will do a
part or parts.
Practice first!
Protein Synthesis Mastery
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Must use:
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All steps in the correct order
Transcription
Translation
Protein
Ribosome
mRNA, tRNA, DNA, Nucleus
Nucleotide
Amino Acid
The 4 differences between DNA & RNA