The Human Genome http://www.teachersdomain.org/cgi-registry/viewfolder.cgi

Chromosomes and DNA Replication Vocabulary: Chromatin Histone Replication DNA polymerase Key Concept: What happens during DNA Replication?

The Review Prokaryotic cells do not have a nucleus DNA molecules are located in the cytoplasm Usually a circular DNA molecule and it is referred to as the cell’s chromosome Eukaryotic cells have a nucleus Can have 1000x more DNA than prokaryotic cells DNA is located in the form of a number of chromosomes # of chromosomes varies widely from species to species

DNA Length DNA molecules are LONG! Ex: E. Coli (prokaryote that lives in human colon) has 4,639,221 base pairs This equals approximately 1.6mm Remember, bacteria are SMALL (1.6um in diameter) It’s like putting a 300m rope into a backpack

How Does DNA Fit? Form a chromosome! DNA coils around proteins called histones and then this chromatin supercoils around itself to form nucleosomes Nucleosomes bunch together to form the visible chromosome

DNA Replication before a cell divides, it must copy its DNA so that all cells have a copy of the genetic instructions this process involves A LOT of enzymes!  each half of the DNA double helix can serve as a "template" for the replication of another DNA double helix molecule The strands are said to be complementary

Video

Hydrogen Bonds Breaking! THE PROCESS An enzyme unwinds & "unzips" DNA (separates the 2 DNA strands) by breaking the Hydrogen bonds between base pairs Hydrogen Bonds Breaking!

the complementary base is inserted to each side of the DNA strand with the help of DNA Polymerase Why does the “blue” always pair with the “green?”

1 nucleotide The sugar-phosphate groups are covalently bonded to the growing DNA chain (new "backbone") COVALENT BOND

an enzyme (DNA Polymerase) will "proof-read" the order of bases & make corrections

SIMPLIFIED VERSION…                                  

A Little More Complicated…