The molecule that carries the genetic information in all living things DNA The molecule that carries the genetic information in all living things

Notes: The Structure of DNA Before the early 1900’s, scientists did not know the chemical make-up of genes

Griffith’s Experiment Griffith was studying what caused pneumonia. He isolated two types of bacteria from mice (R strain & S strain) R Strain- harmless bacteria the had rough edges S Strain- pneumonia causing bacteria that had smooth cultures

Bacterial Transformation Griffith hypothesized that some chemical compound in the heat killed S-strain was transferred into the living R-strain. He called this process transformation

What causes Transformation? Oswald Avery built on Griffith's experiment and treated heat-killed bacteria with enzymes that killed proteins, lipids & RNA and transformation occurred. When bacteria was treated with enzyme that killed DNA, transformation no longer occurred.

Hershey-Chase Experiment Continued DNA contains phosphorus & protein contains sulfur. Hershey & Chase used that information to determine which macromolecule carried genetic material. When the bacteriophage injected its genetic material into the bacteria, phosphorus was found, indicating that DNA was transferred, not protein! Compare the structure of protein with DNA DNA is genetic material found in genes

DNA made of nucleotides Deoxyribonucleic Acid (DNA) is a nucleic acid Nucleic acids are made of subunits called nucleotides

Nitrogenous bases DNA bases have nitrogen in them DNA has 4 different types of bases Adenine (A) Guanine (G) Cytosine (C) Thymine ( T)

Chargaff’s Rule Biologist Erwin Chargaff found that the percentage of Adenine and Thymine in any sample of DNA was always equivalent. The same with Guanine & Cytosine. A=T and G=C known as Chargaff’s Rule

Rosalind Franklin’s X-ray Franklin used a technique called X- ray diffraction to obtain the arrangement of the molecules in DNA The pattern showed a pattern consistent with a helix

James Watson & Francis Crick Watson identified Rosalind's X-ray picture as a double helix. Watson & Crick model showed that the DNA strands had to run opposite of each other. They were antiparallel.

Hydrogen Bonds & Base Pairing The strands are held together by weak hydrogen bonds. Bonds can only for between Adenine & Thymine and Guanine & Cytosine. This is called base pairing

Exit Ticket Explain how Chargaff’s rule & Rosalind Franklin’s X-ray contributed to the discovery of DNA’s structure.

The molecule that carries the genetic information in all living things DNA The molecule that carries the genetic information in all living things

DNA Replication Before the cell is able to divide, the DNA has to be copied. This process is called replication. This happens during S-phase in the cell cycle.

DNA Replication Process The hydrogen bonds between base pairs are broken by an enzyme-- DNA Helicase. Two template strands will be created.

DNA Replication Process Free-Floating nucleotides will be added to the template strand. DNA polymerase joins nucleotides to the template strand to create the complementary strand

DNA Replication Process DNA Polymerase will also proofreads each strand and check for any errors. At the end of DNA Replication, two semiconservative strands are created.

Telomeres Repetitive sequences added Prevents the cells from losing genes.

DNA Replication in Prokaryotes Prokaryotes DNA is circular. Replication has one starting point and it replicates in both directions until it is complete.

DNA Replication in Eukaryotes Replication can begin in hundreds of places on the DNA molecule in Eukaryotes The strand will replicate in both directions until replication is complete.

Describe the function of each enzyme during DNA replication Exit Ticket Describe the function of each enzyme during DNA replication 1) DNA Helicase 2) DNA Polymerase