Genetics

What is DNA? DNA is a nucleic acid (a macromolecule) made up of monomers called nucleotides Deoxyribonucleic Acid can be found in the nucleus of eukaryotic cells but is free- floating in a prokaryote’s cells DNA’s job is to store all of an organism’s genetic information

History of DNA Rosalind Franklin and Wilkins used new X-ray diffraction pictures of DNA in order to determine the structure of DNA Watson and Crick are credited with finally piecing together all the information previously gathered on DNA’s shape and structure. They determined DNA’s structure is a double helix Another scientist named Chargaff analyzed the amounts of different nucleotides found in DNA and noticed a pattern. The amount of A-T was always the same and the amount of C- G was always the same Video

DNA Structure Each nucleotide monomer in DNA is made up of 3 parts A phosphate A sugar (deoxyribose) Nitrogenous base (adenine, thymine, cytosine, guanine) DNA’s double helix structure is made up of 2 strands of nucleotides twisted around each other like a spiral ladder The sides of the ladder are made of phosphates and sugar The rungs of the ladder are made of nitrogenous bases

Nitrogenous Bases Adenine and Guanine are called purines Thymine, Cytosine and Uracil (found on RNA) are pyrimidines

DNA Structure Hydrogen Bonds are found between the bases Adenosine (A) always pairs with Thymine (T) and Guanine (G) always pairs with Cytosine (C) This is called Complementary base pairing Each side of DNA has an opposite orientation. One side ends in a free sugar (3’) and the other side ends in a phosphate (5’) This makes the two strands of DNA antiparallel How the code works? The nucleotide sequence forms your genetic code. Each individual has a different sequence, but about 99.9% of your DNA is identical to one another

What would the complementary base pairs be for this strand of DNA?

DNA Semiconservative Replication Cells prepare for division by replicating DNA Doubles the amount of DNA in the cell by making an exact copy of the existing DNA DNA is in the form of chromatin (loose coils) in the nucleus Enzymes like DNA polymerase and Helicase are needed for replication Free nucleotides are also found in the nucleus

DNA Semiconservative Replication Because DNA is double stranded, one strand can act as a template during replication DNA Replication happens in 3 basic steps Enzymes start to separate or unzip the 2 strands of DNA The enzyme Helicase unzips a portion of DNA called the origin of replication Free nucleotides pair up with a complementary base pair on the original strand of DNA with the help of DNA Polymerase The other unzipped strand also acts as a template for the formation of another new strand of DNA This process is called semi-conservative replication because ½ of a pre-existing DNA molecule is saved No DNA molecule is ever completely new

Accuracy of Replication Replication can occur up to 4000 nucleotides per second Complex organisms replicate DNA with multiple origins of replication, simple organisms like bacteria need only one Repair enzymes detect and correct errors (mutations) that can occur during replication DNA Replication Simulation

RNA- Ribonucleic Acid RNA is composed of monomers called nucleotides Each Nucleotide consists of: A phosphate A sugar (ribose) Nitrogenous base (Adenine, URACIL, guanine, cytosine) RNA is a single stranded Nucleic Acid used for protein synthesis There are 3 types of RNA: Messenger RNA (mRNA), Transfer RNA (tRNA), Ribosomal RNA (rRNA)

http://www.popsci.com/science/article/2013-03/watch- absolutely-beautiful-animated-explainer-dna