DNA: Replication and Mutation
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What is DNA?



DNA = deoxyribonucleic acid
DNA is the “blueprint” for the cell
contains the instructions that tells the
cell how to do things and what to make
DNA is like blueprints for making a city, which
in this case is the cell
Amoeba Cell
What is DNA made of?

DNA is made up of 4 bases:
–
Adenine (A), Thymine (T), Cytosine (C), Guanine (G)
Rules for DNA Bases:
1. A pairs with T
2. G pairs with C
“Chargaff’s Rules”
Structure of DNA


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DNA is made up of two
strands (double
stranded)
Each strand has the
bases connected to a
PHOSPHATE
BACKBONE
The two strands wrap
around each other in a
winding staircase
manner (helix)
Models of DNA
ACTUAL Pictures of DNA
DNA Replication


In order for you to survive,
your cells need to replicate
themselves. In order for
them to do that, they need
to replicate their DNA
Every cell in your body has
the same DNA, because
every time one of your cells
divides, it makes a copy of
its DNA to give to the new
daughter cells
How does DNA replicate?

The DNA is unzipped and the original strands
are used to help make the new molecules –
See Demonstration
What are mutations?

MUTATIONS are any
changes in the
sequence of bases of
DNA
Mutations
Mutations DO
COULD
NOT
lead
lead to
to this
this
Colon cancer cells
How do mutations occur?



Sometimes during replication,
the cell makes a mistake and
adds the wrong base
When the cell replicates its DNA
again, the two strands that are
produced are no longer exactly
the same
This usually will cause the new
cell to die, but sometimes it can
cause the cell to divide when it is
not supposed to  cancer
How do mutations occur?
Replication
What can cause mutations to happen
more often?