1. DNA & Populations http://www.flickr.com/photos/bwjones/4344712708/

2. 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)

3. 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/

4. Why is this important? 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 You can discover the order in which islands were colonized Example: Bird A: GTCC Bird B: GACC Bird C: GAGC Bird D: GAGG http://www.flickr.com/photos/arcticpuppy/3020931978/