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DNA & Populations
http://www.flickr.com/photos/bwjones/4344712708/
Let’s Review


What is a cell? How many cells
make up an organism?
What is the nucleus?
What is DNA? What is it made up
of?
 What is a sequence of DNA called?
 Why is DNA important?
 What is one way that DNA
sequences can change?

Image sources:
http://www.jimmyjanesays.com/sketchblog/2007/04/plant-cell.html (Plant cell)
http://www.biologycorner.com/bio1/DNA.html (DNA diagram)
How do we know gene sequences?


Geneticists use a technique
called gel electrophoresis
This technique breaks apart a
gene in a predictable way,
allowing scientists to piece
the sequence back together
http://www.flickr.com/photos/micahb37/3080247531/
http://www.flickr.com/photos/14508691@N08/1472624764/
Why is this important?

http://www.flickr.com/photos/arcticpuppy/3020931978/
DNA sequences can tell you how species are
related

Species – organisms that can interbreed

Isolation can cause the formation of new species
Species with more similar sequences are more closely
related
Example:
 You can discover the order in which islands were
Bird A: GTCC
colonized

Bird B: GACC
Bird C: GAGC
Bird D: GAGG