Download DNA - Cobb Learning

Donations Requested
We could use some…
• Gummy Bears (we need lots of these)
• Red Twizzlers
• Black Twizzlers
Why? Well…we are going to be making models
DNA!
of…
What is that…here we go
Mr. Blacher's 7th Grade Biology
Genetics
The study of heredity…whatever that
means.
Heredity-The passing of traits from parents
to progeny (offspring)
Mr. Blacher's 7th Grade Biology
DNA
1. It’s a nucleic Acid…specifically it’s
Deoxyribonucleic Acid.
2.
This is the substance (it’s a
molecule) that determines
inherited characteristics.
What’s that mean…to a human!
Inherited…means it you get it from mom and dad.
A characteristic is something like…eye color, the
shape of your face…your blood type.
Mr. Blacher's 7th Grade Biology
The Parts of DNA
•
•
1.
DNA is made up of NUCLEOTIDES
NUCLEOTIDES are made of three parts:
A Pentose Sugar: Deoxyribose…it’s a sugar
with 5 carbons (penta=5, -ose=sugar).
2. A Phosphate Group…that’s a compound with a PO4 group.
3. One of four different Nitrogenous Bases:
Adenine Thymine Cytosine Guanine
A
T
C
G
Mr. Blacher's 7th Grade Biology
The Structure of DNA
• The DNA molecule
looks like a ladder that
has been twisted.
• This shape is called a
DOUBLE HELIX.
• 1950 Irwin Chargaff
figures out that there is
always the same amount
of adenine as thymine,
and there was the same
amount of cytosine as
guanine…smart human I
gotta say.
Mr. Blacher's 7th Grade Biology
*Extremely smart dudes/dudettes warning*
1. Rosalind Franklin: used X-ray diffraction to
determine that the DNA molecule was a spiral.
2. James Watson & Francis Crick: figured out
that the spiral was a double helix (TWO
spirals…a twisted ladder) and made a model.
Let’s see you use the properties of high
energy electromagnetic waves to discover
the shape of an organic
macromolecule…yeah…that’s what I
thought.
Mr. Blacher's 7th Grade Biology
The Structure of the Double Helix
• The Rails of the ladder are alternating
molecules of sugars and phosphates.
• The Rungs of the ladder are the
nitrogen (nitrogenous) bases that are
attached to the sugars.
Mr. Blacher's 7th Grade Biology
Here’s What it Looks Like
Mr. Blacher's 7th Grade Biology
Here’s Where it Fits in With
Cells…and YOU!
Mr. Blacher's 7th Grade Biology
Here’s Another View…
Mr. Blacher's 7th Grade Biology
Genes are…
• A GENE is a set of chemical instructions for
assembling a protein. DNA is the molecule that
carries these genetic instructions.
• Within a gene, each group of three nitrogenous
bases codes for one amino acid.
• A sequence of amino acids is linked to make a
protein.
• Proteins are fundamental to the function of
cells and the expression of traits.
Mr. Blacher's 7th Grade Biology
Here’s The Relationship To
Chromosomes
Mr. Blacher's 7th Grade Biology
Replication
• When DNA copies (every time a cell divides), it
splits down the middle separating in between the
base pairs.
• The new strand of bases is complimentary…that
means that where there’s an A (adenine), there
will be a T (thymine) to match with it. Where
there is a C (cytosine), there will be a G
(guanine) to match with it.
• Write the complimentary strand for this
sequence: GAATTCGCGGAT
Mr. Blacher's 7th Grade Biology
Here’s What You Should Have 
GAATTCGCGGAT
CTTAAGCGCCTA
Mr. Blacher's 7th Grade Biology
Enzymes
(an enzyme is a protein…look for the
–ase)
• *There are a number of enzymes that are
involved in this process:
– DNA helicase: unzips the DNA
– DNA polymerase: lines up the new bases
– DNA ligase: “glues” sections together
*Bonus info…no extra charge , and no…you don’t
need to know it. But some day…
Mr. Blacher's 7th Grade Biology
Genetic Engineering
• By understanding DNA we can…you tell
me…it’s in your book 
• We’re gotta get waaaay more into this part when
we hit GENETICS…which…is gonna be soon!
Mr. Blacher's 7th Grade Biology