DNA The Language of Life

How Did We Find It?? Fredrick Griffith conducted an experiment with mice Fatal strain kills mice Non fatal strain doesn’t kill it Heated (dead) fatal strain doesn’t kill it Mix of heated (dead) fatal strain and healthy non-fatal strain kills it Why?

I know! It…..it…… TRANSFORMS!! So How Did We Discover It Was DNA? Frederick Griffith, Biologist Oswald Avery, Biologist Optimus Prime, Autobot Is this guy serious?? I know! It…..it…… TRANSFORMS!! Don’t worry, I got this.

So How Did We Discover It Was DNA? PROCESS OF ELIMINATION! Avery used protein – destroying enzymes with Griffith’s experiment, and nothing changed. He switched to DNA – destroying enzymes, and the bacteria didn’t become fatal. DNA DID IT! This lead them to believe that DNA was the source of the cell’s genetic material, and the cause of traits that are “heritable”, which means they can be passed down from generation to generation.

Hershey And Chase Solidify Avery’s Findings Don’t Worry, Avery We’ve Got Your Back. Hershey and Chase tagged the DNA in a virus with a radioactive isotope, and traced it into the cell. They also tagged the protein that makes up the virus, just to make sure it was the DNA that was passing on genetic information, not the protein.

Watson And Crick Show Us What It Looks Like Using the results of their own research, and data from the research they, um, “borrowed” from Rosalind Franklin, they showed how DNA comes together and forms a double-helix structure. She was NOT happy about that.

WHAT IS DNA MADE OF? DNA stands for Deoxyribonucleic Acid It is made of nucleotides. The nucleotide has 3 components: a ring-shaped sugar called “deoxyribose”, a phosphate group, and a nitrogenous base.

MEET THE NITROGENOUS BASES THE PURINES Double-ring structure Adenine and Guanine THE PYRIMIDINES Single-ring structure Thymine and Cytosine Purines will ONLY bond with pyrimidines, and vice-versa. This is called “Chargaff’s Rule”. Adenine only bonds to Thymine Cytosine only bonds to Guanine

REMEMBER! In DNA, Adenine only bonds to Thymine, and Cytosine only bonds to Guanine!! These are called “Complimentary Base Pairs”.

These Complimentary Base Pairs join together via hydrogen bonds to form the double-helix shape that we all know and love.

SEMICONSERVATIVE REPLICATION

DNA has two sides, and each end is either a 3’ (prime) or a 5’. The sides run ANTIPARALLEL, or opposite. One end starts at 3’, the complimentary strand starts at 5’.

HOW DO WE MAKE MORE?? When DNA replicates, DNA Helicase “unzips” it, breaking it at the base pairs. DNA Polymerase works its way down the open ends, adding new base pairs, until there are 2 new strands of DNA made. V

HOW DO WE MAKE MORE?? DNA Polymerase can only write in the 3’ to 5’ direction. This works great for the LEAD strand (top) but not for the LAGGING strand (bottom) DNA Polymerase writes the LAGGING strand in small sections called OKAZAKI FRAGMENTS.

HOW DO WE MAKE MORE?? DNA Ligase acts as “glue” , adding phosphates to the nucleotides, giving them a structured backbone.