2 Biology 10 1 15 Thursday October 1 2015 The Model Makers Watson Crick and the Structure of DNA Watson was a bit of a scoundrel The double Helix Watson is still alive These two scientists won noble prize DNA Puzzle DNA was first discovered in cell nuclei in the 1860 s The first DNA molecule was isolated from pus In the 1950 s DNA was determined to be the genetic material They were saying that genetic material had to be something like a protein because those are made up of thousands of amino acids while DNA is composed of nucleotides which are made up of a sugar phosphate and nitrogenous base there are four bases Adenine Thymine Guanine Cytosine people didn t know what the structure of DNA was but they were thinking that it was the genetic material there was a race to figure out more about DNA Watson Crick and Franklin In 1951 Watson Crick built scale models of DNA Rosalind Franklin had been working in France and created X Ray diffraction patterns of crystallized DNA She discovered the twisting helical structure and two strands that ran in the opposite direction and that the phosphate groups are on the outside Chargaff Base Pairing Rules Chargaff determined in every DNA molecule there were always equal amounts of A T bases and G C bases Double Helix Model using franklin s unpublished x ray picture Watson and crick determined DNA structure in 1953 2 strands of nucleotides form a helix that spiral in opposite directions nitrogenous bases form pairs on the inside of the helix via hydrogen bonding Adenine with Thymine Guanine with Cytosine Chargaff s rule of base pairing Nitrogenous Bases Adenine and Guanine are the Purines and are double ring bases Thymine and Cytosine are Pyrimidines are single ring bases Watson and Crick Model of DNA structure Epilogue to DNA story Watson Crick and Wilkins received Nobel Prize in 1962 1 Thursday October 1 2015 CHAPTER 7 DNA Structure and Replication Innocence Project There are many stories where DNA evidence which didn t exist in the 1970 s is now proving the innocence of people that have been incarcerated for 40 years Over 300 people have been freed by 2 lawyers that use DNA evidence Conviction movie DNA as evidence Deoxyribonucleic Acid molecule of inheritance common to all life forms instructions for organisms structure located in the nucleus in eukaryotes Chromosomes are made of DNA and protein A single large DNA molecule wrapped around proteins histones humans have 23 pairs of chromosomes in somatic vels total of 46 23rd pare are sex chromosomes XX female XY male one is inherited from mother and one from father if you inherit chromosome one from your mother you will inherit a comparable chromosome from your father DNA Structure 2 strands of nucleotides form DNA molecule Nucleotides consist of a sugar phosphate and nitrogenous base nitrogenous bases consist of Guanine Cytosine Thymine Adenine The sugar and phosphate are linked to form the dna backbone The bases pair by H bonding to form the internal rungs The two strands twist around each other to form a double helix DNA Sequences are Unique the 4 nitrogenous bases are repeated in different combinations in each individual Forensic scientists use the order of DNA nucleotides to identify perpetrators DNA profile visual representation of a persons unique DNA sequence Making more DNA all organism s fluids and tissues contain cells with DNA However sometimes the samples are too small to extract sufficient amounts of DNA Polymerase Chain Reaction PCR a technique used to replicate and thus amplify a specific DNA segment Mullis developed in mid 1980 s and got a noble prize in 1993 DNA replication a process by which cells can make an identical copy of a DNA molecule at a rate of 1000 nucleotides per second 2 Thursday October 1 2015 Complementary 2 strands of DNA molecule pair up in a consistent pattern A with T G with C Each DNA strand serves as a template for creation of a new complementary strand Steps of DNA Replication 1 H bonds holding together nucleotide base pairs break and DNA helix is unwound 2 DNA polymerase is and enzyme that pairs nucleotides A with T and C with G to each individual DNA strand produces 2 new molecules of DNA 3 Each replicated DNA molecule is made up of one new strand and one original strand DNA replication is said to be semi conservative PCR pcr is similar to DNA replication but it occurs in a test tube Test tube contains DNA Nucleotides DNA polymerase primers short DNA segments that bind to DNA Tube is heated to separate the strands and then cooled to allow nucleotide addition PCR can make billions of copies of specific DNA regions DNA Profiling a Genome is a complete set of genetic instructions encoded in an organisms DNA It would be very difficult to sequence an entire human genome 3 billion nucleotide base pairs Forensic Scientist use a short cut by sequencing short segments of DNA called Short Tandem Repeats repeated DNA sequences called STRs Every person has STRs on their chromosomes but the STRs vary in length from person to person This is where our STR s came from we inherit half from mom and half from dad Coding Regions the DNA sequences that contain instructions for making proteins The Non Coding Regions have been called Junk DNA DnNA sequences that do NOT contain instructions for making proteins Vary between individuals proving a genetic fingerprint to identify a unique person Gel Electrophoresis visualized with fluorescence Technique used to separate DNA fragments based on size to create a unique DNA profile Shorter travel farther longer travel less Uses of DNA profiles 3 Thursday October 1 2015 Uses of DNA Profiling US Database contains more than 10 million profiles from 15 specific STR Regions Likelihood that 2 unrelated individuals have same DNA Profile for 15 STRTs is 1 in quintillion DNA profile database has been used in more than 190 000 cases More than 300 prisoners have been exonerated by the Innocence Project Chapter 8 Genes to Proteins Medicine from Milk Pharming using genetically modified animals to manufacture therapeutic drugs Transgenic Animal an animal that has genes from a different species The Human protein antithrombin is isolated from transgenic goat s milk Advantages of transgenic antithrombin larger amounts than from human blood Consistent Supply you can t always rely on humans to provide consistent a useable donations less risk of transmitting disease less expensive than cell culture Protein Structure and Function Antihrombin is a protein