CHROMOSOMES & DNA REPLICATION THE SOURCE OF GENETIC INFORMATION

PROKARYOTIC CELLS Prokaryotic Cells = Lack nucleus and many organelles found in eukaryotes DNA is found in cytoplasm of prokaryotes Single circular DNA that has all of cells genetic information, a plasmid

EUKARYOTIC CELLS Eukaryotic Cells = DNA is found in nucleus in the form of chromosomes. Number of chromosomes varies from one organism to another Humans have 46, fruit flies has 8 and giant sequoia trees have 22 1000X more DNA than prokaryotic cells: more complex.

CHROMOSOME STRUCTURE DNA in Eukaryotes is packed tight. A human cell contain 1000X more base pairs than 1 bacteria. Nucleus contains more than 6 feet of DNA. Eukaryotic chromosomes have both DNA and proteins packed together of from a substance called chromatin Chromatin consists of DNA that is tightly coiled around proteins called histones. Histones = proteins that DNA wraps around.

DNA Section 12-2 Nucleosome Chromosome DNA double helix Coils Supercoils Histones Go to Section:

DNA REPLICATION Replication = duplicating or copying the DNA before the cell divides. How is it done? DNA separates into 2 strands Then forms new complementary strands (according to base rules). Complimentary strands ofDNA have opposite bases. For example: A always pairs with T. If one strand has the base A, then the complimentary strand has T.

Each strand of the double helix serves as a template, or model for the new strand. Replication is carried out by a series of enzyme reactions. They unzip the double helix and expose the complimentary bases on the inside. Now they can be copied

DNA REPLICATION Section 12-2 Go to Section: New strand Original strand DNA polymerase Growth DNA polymerase Growth Replication fork Replication fork Nitrogenous bases Original strand New strand Go to Section:

HOW DOES REPLICATION OCCUR? DNA polymerase - enzyme helps unzip DNA. Weak hydrogen bonds break and strands unwind. http://www.dnatube.com/video/365/DNA-Replication

REPLICATION http://www.fed.cuhk.edu.hk/~johnson/teaching/genetics/animations/dna_replication.htm http://www.johnkyrk.com/DNAreplication.html

DNA replication interactive http://www.pbs.org/wgbh/aso/tryit/dna/#

In your own words: How is DNA replicated? _______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ BE READY TO SHARE WITH THE CLASS