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UNIT 3: DNA—THE GENETIC MATERIAL OF LIFE
WHAT IS DNA?
 Stands for: __________________________________________________________

DNA is a molecule that stores the ________________________________________________ in all organisms

DNA is stored in the __________________________ of your cells
FUN DNA Facts!
DNA is too
small to see,
but under a
microscope
it looks like a
twisted up
ladder!
DNA Stands for:
D: Deoxyribose
N: Nucleic
A: Acid
Every living thing has DNA. That means that YOU
have something in common with a zebra, tree,
mushroom, and beetle!
THE STRUCTURE OF DNA
DNA Structure
DNA is a long chain of units made of ______________________________
Each nucleotide has three parts:
1. ________________________________ (one phosphorus/3 oxygens)
2. ________________________________ (ring-shaped sugar)
3. ________________________________
There are ___________________ types of nucleotides—based on what type of _____________________________ they
have
Structure of nucleotides:
_________________________________
_____________________:
Adenine (A)
Guanine (G)
Cytosine (C)
Thymine (T)
_________________________________
One molecule of DNA contains BILLIONS of nucleotides, but there are only 4 types:
--_____________________A
--_____________________G
--_____________________C
--_____________________T
The letter refers to the ___________________________ as well as the nucleotide
BASE PAIRING
DNA is a ___________________________________ structure—this means that there are two strands of DNA
that wind together like a twisted ladder
The strands are bonded together at the ______________________
The bases always pair up in the same way based on _________________________________________________:
Adenine bonds with Thymine
Adenine
Thymine
Cytosine bonds with Guanin
THE DOUBLE HELIX
Bases
Sugar
Phosphate
chain
The structure of DNA consists of two strands wrapped around each other in a double helix
So, if one strand is……. what is the other strand based on base pairing rules?
AT C GA–
T–
A–
G–
C–
T ADNA REPLICATION
DNA REPLICATION
Before a cell divides, it must make a _______________ of its DNA so the new cell has a full set of DNA
Steps of DNA Replication:
1. DNA is _____________________________________
2. __________________________________ adds nucleotides, according to base pairing rules
3. The strand is ___________________________ as nucleotides are added, and mistakes can be
fixed if the wrong base was added
 A mistake is called a _________________________
4. DNA polymerase continues adding nucleotides until _________________ signal is reached
DNA Replication in Action
TRANSCRIPTION
RNA (this molecule is used during transcription)
RNA: _______________________________________________
--Chain of nucleotides made of:
o ____________________________________
o
____________________________________
o
____________________________________
--It’s a ________________________________________________ of DNA that is used then destroyed
DNA vs RNA:
(both have a sugar, phosphate & base)
DNA
RNA
Its sugar is _____________________________
Its sugar is _________________________________
Bases are : Adenine, Thymine, Guanine & Cytosine
Bases are Adenine, Uracil, Guanine, & Cytosine
____________________strand of nucleotides
____________________strand of nucleotides
Transcription:
1. Copying a ______________________________________ to make a
complementary strand of RNA
2. This is catalyzed (allowed to happen) by__________________________
Basic Steps of Transcription in Cells:
1. DNA strands unwind
2. RNA polymerase copies one strand of_____________and creates a complementary strand of
_________________________________ (known as mRNA)
3. Once the gene has been copied, ___________________________________________________
4. mRNA moves out of the nucleus and into the ____________________________________
Types of RNA: Made during transcription, used during translation
o ____________________________________(mRNA)
o ____________________________________(rRNA)
o ____________________________________(tRNA)
TRANSLATION
TRANSLATION
 Process that converts (translates) ________________________into ____________________________ —called
protein synthesis
 mRNA is a message that codes for a _____________________________ when it attaches to a ribosome in the
cytoplasm of the cell
 Each combination of 3 nucleotides (known as a _______________) on the mRNA codes for an
__________________________________ —groups of amino acids become proteins in the cell
Steps of Translation:
1. mRNA moves out of _________________________
and into the ____________________________
2. mRNA attaches to___________________________
3. Transfer RNA (tRNA) decodes the mRNA
into ________________________________, which
link together into __________________________
4. Protein (chain of amino acids) detaches from ribosome
and goes off to work in the cell
Genetic Code
tRNA matches each ______________ in mRNA to three nucleotide bases called _________________ on tRNA.
This anticodon has a specific amino acid attached that will eventually form a chain of amino acids to make a
protein :
• There are 64 possible 3 letter combinations BUT only 20 amino acids….
• SO, some Codons code for more than one amino acid
Codon
Anticodon
Different codons code for different amino acids!!
TRANSCRIPTION VS. TRANSLATION REVIEW
Transcription
Process by which
genetic information
encoded in ___________ is
copied onto ____________________
Translation
Process by which
information encoded in
___________ is used to
assemble a protein at a
ribosome
Occurs in the ____________________
Occurs on a ______________________
_______________
______________
_______________
______________
MUTATIONS
A Mutation is a ____________________________________________________________________________
It’s a mistake made during _____________________________ or ________________________________
Can be:
1. Harmful: _______________________________________________________
2. Helpful: ________________________________________________________
3. Neutral: ________________________________________________________
Passing on Mutations
If a mutation occurs in a ______________________________________
cell, the mutation IS PASSED on to offspring
If a mutation occurs in a ______________________________________,
it only affects the organism and IS NOT PASSED on to offspring