1. CATALYST Read the case study on pg 158 In your notebook, answer the following questions in complete sentences: – How was DNA fingerprinting used in this case? – Only half of Andrew’s DNA fingerprint is the same as his Christiana’s DNA. Is that enough to prove, beyond a doubt, that Andrew is her son? – Why did they run a DNA fingerprint on Christiana’s other children? 1

2. 2 Chapter 7 DNA Fingerprinting By the end of this chapter you will be able to: explain how crime scene evidence is collected and processed to obtain DNA describe how radioactive probes are used in DNA fingerprinting explain how DNA evidence is compared for matching explain how to use DNA fingerprinting to identify DNA from a parent, child, other relative, or a non- related individual All Rights Reserved South-Western / Cengage Learning © 2009

3. 3 Introduction and History of Biological Evidence in Forensics DNA fingerprinting, also known as DNA profiling, is used in criminal or legal cases with a high degree of accuracy. Biological evidence such as blood, saliva, urine, semen, and hair is examined for the presence of inherited traits.

4. 4 Introduction and History of Biological Evidence in Forensics DNA is the blueprint of life and contains the genetic material of a cell. DNA holds all the information and instructions needed for a cell to make proteins and replicate Genetic information is stored in molecules of DNA making up structures called chromosomes – Found in the nucleus of cells in the human body.

5. Rosalind Franklin – 1950’s English Chemist – Used X-ray crystallography to create image of DNA Looked like rungs, like those on a ladder between two strands that are side by side ‘X’ shape suggested a spiral or helical molecule 5 Introduction and History of Biological Evidence in Forensics

6. Watson & Crick – 1953 used Franklin’s picture to make an accurate 3-D model of DNA 6 Introduction and History of Biological Evidence in Forensics

7. DNA Structure DNA = deoxyribonucleic acid Polymer consisting of thousands of smaller, repeating units called nucleotides 7

8. DNA Nucleotides A DNA nucleotide is composed of three parts: 1. Phosphate group: made of oxygen, hydrogen, and phosphorous 8

9. DNA Nucleotides 2. Deoxyribose: 5-carbon sugar made up of carbon, hydrogen, and oxygen. 9

10. DNA Nucleotides 3. Nitrogenous base: made up of carbon, oxygen, hydrogen, and nitrogen 3. There are 4 types: Adenine (A) Guanine (G) Cytosine (C) Thymine (T) 10 purines pyrimidines

11. DNA Structure DNA is made up of two strands of nucleotides that form a structure that looks like a twisted ladder which we call a double helix. 11

12. DNA Structure Double helix – Backbone (sides of ladder): polymer with alternating sugar- phosphate sequence – Connected by the nitrogenous bases held together by hydrogen bonds 12 phosphate sugar bases H Bond

13. 13

14. Base Pairings Chargaff’s rule – Erwin Chargaff (1950) – Amount of adenine (A) equals the amount of thymine (T) – Amount of guanine (G) equals the amount of cytosine (C) 14

15. Base Pairings Complimentary Base Pairings: every base pair consists of one purine (A or G) and one pyrimidine (T or C) – Adenine (A) always pairs with thymine (T) forming 2 hydrogen bonds  A-T – Guanine (G) always pairs with cytosine (C) forming 3 hydrogen bonds  G-C 15

16. DNA Structure When the base pairs of the DNA strands form a double helix, the strands are considered to be complimentary – if the bases in a section of one strand is CGTCTA, then the order of bases in the complementary section of DNA in the other strand is GCAGAT 16 CGTCTA GCAGAT

17. DNA Structure DNA makes up structures known as chromosomes – DNA coils into chromosomes around proteins – Chromosomes are found in a cell’s nucleus 17

18. Human DNA There are 23 pairs (total of 46) of chromosomes in the nucleus of most human cells (except sperm and egg cells) – One chromosome in each pair is inherited from the mother and the other is inherited from the father 50% of a person’s DNA come from each parent 18

19. Human DNA Nuclear DNA: found in the chromosomes – Virtually identical in all cells of the human body – DNA fingerprints are derived from nuclear DNA Mitochondrial DNA: found in the mitochondria – Only inherited from the mother – Can be used to identify a person’s mother 19

20. Genes & Alleles Each chromosome contains many genes – Genes: DNA sequences that have instructions that determine our inherited characteristics of traits Genes determine our characteristics (i.e. blue eyes, brown hair, Used to produce proteins or RNA (ribonucleic acid) 20

21. Genes & Alleles We can have two versions of each gene – Allele: one of the alternative forms of the genes – One allele comes from the mother and the other comes from the father. Example: – One allele codes for normal hemoglobin while the other codes for abnormal hemoglobin 21

22. DNA Encoded DNA (exons): DNA used to make up proteins and other molecules Unencoded DNA (introns): DNA that does not produce proteins or RNA molecules – Important in gene splicing 22

23. DNA The human genome is the total amount of DNA in a cell (both nuclear and mitochondrial) There are 3 billion base pairs and 23,688 encoded genes in the human genome – That is less than 1.5% of the DNA in the genome (more than 98.5% is non-coding) If you took out all of the DNA in all of your cells and stretched the strands end to end you could reach the moon… – 6000 times! 23