CHROMOSOMES & DNA REPLICATION THE SOURCE OF GENETIC INFORMATION MURTAUGH 1B LIVING ENVIRONMENT

ESSENTIAL QUESTIONS How is DNA organized? Where does DNA replication occur within a cell? How does DNA reproduce? When DNA replicates are the two new strands completely new?

VOCABULARY Prokaryotic Cells-less complex cells that have no true nucleus, genetic material (DNA) is found in the cytoplasm of the cell Eukaryotic Cells- more complex cell with organ bound organelles, has a true nucleus, DNA found in the nucleus of the cell N-CHOP: the 5 elements that make up DNA- Nitrogen, Carbon, Hydrogen, Oxygen, Phosophorus Chromosome: thread-like structure that contains sections of DNA, the number of these identifies the type of an organism, organizes genetic material (DNA) Replication- the copying process that makes two identical replicas from an original DNA molecule. Mutation- is a change or mistake in the nucleotide sequence of DNA. Daughter stand- the replicated strand from a parent (original) strand of DNA during replication

PROKARYOTIC CELLS AND DNA Prokaryotic Cells = Lack an organized nucleus DNA found in cytoplasm Single circular DNA

EUKARYOTIC CELLS AND DNA Eukaryotic Cells = DNA found in nucleus Number varies from one organism to another 1000X more than prokaryotic cells

DNA DNA is made up of the elements: Nitrogen, Carbon, Hydrogen, Oxygen, and Phosphorus Think “N-CHOP” A human cell contain 1000X more base pairs than 1 bacteria. Nucleus contains more than 1 meter of DNA. How is all this genetic material organized?????

WHY ARE CHROMOSOMES IMPORTANT? Not only does chromosomes ensure that all that genetic material fits into every cell in your body, the number of chromosome pairs tells you what type of organism it is. Ex) Human- 46 chromosome pairs Corn – 20Gorilla- 48 King Crab- 208 Dog- 78 With sexual reproducing organism –half of these chromosomes come from each parent

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

DNA REPLICATION Replication – duplicating of the DNA before the cell divides. Occurs in the nucleus DNA separates at the replication fork into 2 strands Then forms new complementary strands (according to base rules). Each strand serves as a template using base for corresponding nucleotides to make an IDENTICAL Copy

REPLICATION FACTS Carried out by a series of enzymes. These enzymes proofread and correct mistakes If mistakes occur, these are called mutations. The new error rate for DNA that has been proofread is 1 in 1 billion base pairing errors The new strands are called daughter stands.

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

HOW DOES REPLICATION OCCUR? 1. With the help of an enzyme (Helicase), DNA unwinds and unzips -hydrogen bonds are broken at the replication fork. 2. Complimentary nucleotides are paired with the original strands acting like templates with another enzyme (DNA polymerase) proofreading it and new hydrogen bonds forming. 3. The nucleotides are connected with sugar and phosphate backbone making new “daughter” strand.

REPLICATION LOOK #1 Notice that the end results with two complete DNA, HOWEVER, both contain one original (parent) stand and one new (daughter) stand.

REPLICATION LOOK #2