Understanding DNA: The Blueprint of Life

1. DNA Created from several PowerPoints on the state’s website

2. WHAT IS DNA? • Deoxyribonucleic acid – DNA • Inside each of 60 trillion cells in the human body are strands of genetic material called chromosomes • On these chromosomes are nearly 30,000 genes • The gene is the fundamental unit of heredity. It instructs the body cells to make proteins that determine everything from hair color to susceptibility to disease

3. More about DNA • DNA is a polymer

4. Discovery of DNA • James Watson and Francis Crick – 1950s • Deduced the structure of DNA • Controls the genetic traits of all living cells, plants and animals • Four types of bases associated with DNA • Adenine, cytosine, guanine, and thymine

5. DNA is composed of two DNA stands coiled into a double helix • A opposite T • G opposite C • Known as complementary base pairing

6. 1985 – discovery that portions of the DNA structure of certain genes are as unique to each individual as fingerprints • Alec Jeffreys and colleagues at Leicester University named process for isolating and reading DNA markers DNA fingerprinting

7. All of the human chromosomes taken together contain about 3 billion base pairs. From these numbers, we can begin to appreciate the diversity of DNA and hence the diversity of living organism consisting of the alphabet • A,T,G,C

8. DNA at work • Inheritable traits are controlled by DNA arise out of its ability to direct the production of complex molecules called proteins. • Proteins are made by linking a combination of amino acids • 20 known amino acids

9. Evidence for a Genetic “Factor” • 1928 – Frederick Griffith’s“Transforming Factor” Experiment • Conclusion: “Something” from Heat-treated Strain 1 “transformed” Strain 2 to become deadly

10. DNA is Proven to be that Genetic Factor • 1944 – Oswald Avery and colleagues focused on two of the genetic factor candidates: protein and DNA • Repeated Griffith’s experiment, but with a modification   Proteases Mouse dies   DNases Mouse lives Conclusion – DNA is the transforming, thus genetic material

11. DNA REPLICATION • DNA replication begins with the unwinding of the DNA strands in the double helix. • Each strand is then exposed to a collection of free nucleotides. • Letter by letter , the double helix is recreated as the nucleotides are assembled in the proper order, base pairing

12. DNA polymerases are enzymes that assemble a new DNA strand in the proper base sequence determined by the original or parent DNA strand. • PCR polymerase chain reaction – using DNA polymerases to copy a DNA strand located outside a living cell – new lab technology

13. Small quantities of DNA or broken pieces of DNA found in crime-scene evidence can be copied with the aid of a DNA polymerase • A DNA Thermal Cycler is used for the copying process • Sample size no longer a limitation in characterizing DNA recovered from csevi

14. R/ship b/t base letters on a DNA strand and the type of protein specified for manufacture by the sequence of these letters is called the genetic code

15. Key to understanding DNA typing lies in the knowledge that within the world’s population numerous possibilities exists for the number of times a particular sequence of base letters can repeat itself on a DNA strand. Possibilities become greater when one deals with two ch. Each containing different lengths of repeat sequ.

16. It’s the length differences associated with DNA strands or RFLPs(Restriction Fragment Length Polymorphisms) that allow forensic scientists to distinguish one person from another

17. Once DNA molecules have been cut up by the restriction enzyme, the resulting fragments must be sorted out – by electrophoresis – DNA from various sources, cut up by restriction enzymes, is placed in an separate lanes on an electrophoretic gel and subjected to an electric field

18. During this process, DNA fragments will migrate across a gelcoated plate – fragments are chemically treated so that the strands separate from each other • RFLP DNA typing- used in impeachment trial of President Bill Clinton – semen stained dress of Ms. Lewinsky pg 372

19. SIGNIFICANCE • About 25% of the DNA exams conducted by the FBI lab since 1989 have excluded suspects identified by police as the source of DNA evidence collected from the crime scene

20. In the Beginning….. • The world of science debated on what the genetic material was • Some thought it was protein • Others believed it was DNA

21. The Structure of DNA Continued • Phosphate Group – provides the “backbone” of DNA 5’ end (5 prime end) • Sugar – called a deoxyribose; also part of the DNA “backbone” 3’ end (3 prime end) • Backbone of DNA called the sugar-phosphate backbone

22. One of the most publicized cases performed on human remains was the id of the individual buried in the tomb of the Vietnam War’s unknown soldier

23. Pairing of Bases • In DNAG hydrogen bonds with C • T hydrogen bonds with A G C C A T G T A C G T A T C G G T A C A T G C A T A

24. Were believed to belong to First Lt. Michael J. Blassie, whose A-37 warplane was shot down near An Loc, South Vietnam, in 1977 • 1984 – US Army Central Identification Lab – failed to identify remains by physical characteristics

25. 1998 – Blassie family, mtDNA analysis analysis and was confirmed to be consistent with Lt. Blassie’s family

26. Combined DNA Index SystemCODIS • All 50 states have legislatively mandated the collection of DNA samples from convicted offenders of particular crimes and the establishment of DNA databases for law enforcement purposes

27. CODIS – computer software program developed by the FBI that maintains local, state, and national databases of DNA profiles from convicted offenders, unsolved crime scene evidence, and profiles of missing persons • READ STORY page 390

28. Luminol – can be used to locate traces of blood and areas that have been washed nearly free of blood without compromising the potential for DNA typing • READ CASE page 395

29. Criminalistics Chapter 13