12-2: CHROMOSOMES AND DNA REPLICATION Biology 2

Prokaryotes lack a nucleus and organelles DNA is located in cytoplasm and Chromosomes Prokaryotes lack a nucleus and organelles DNA is located in cytoplasm Most have single circular DNA Eukaryotes are more complex DNA is located in nucleus, as chromosomes Number of chromosomes varies between species

EUKARYOTE DNA PROKARYOTE DNA

DNA is wrapped tightly around histones (forms chromatin) and Chromosomes DNA is wrapped tightly around histones (forms chromatin) CHROMATIN: granular material visible within the nucleus; consists of DNA tightly coiled around proteins Chromatin is wrapped up tightly to form loops and coils As it wraps tighter and tighter, it forms the X structure of chromosomes

HOW IS DNA PACKAGED http://www.youtube.com/watch?v=9kQpYdCnU14&feature=relmfu

CHROMOSOME ORGANIZATION

Before a cell divides it creates a “copy” of DNA during replication REPLICATION: copying process by which a cell duplicates its DNA DNA separates into 2 strands, and “copies” the pattern to create another strand Must use base pairing rules (A=T, C=G) to make new strand Goal of replication is to have 2 complete sets of DNA for cells DNA Replication

DNA REPLICATION http://www.youtube.com/watch?v=zdDkiRw1PdU

Section Assessment Prokaryotes lack a __________ and __________ , DNA is located in __________ Eukaryotes are more __________ , DNA is located in __________ , as __________ Goal of replication is to have ______________ of DNA for cells

Bill Nye – Genes and Chromosomes http://www.youtube.com/watch?v=HqoQoJMG0Lc