DNA Is In All of Your CellsBody Fluids and Tissues

• Blood• Semen• Saliva• Perspiration• Tissue• Bones and Teeth• Hair (if there is tissue on

the root)• Urine, Feces, Vomit

You Leave DNA Everywhere

Cigarette buttsStamps and Envelope flapsDrinking cups and BottlesCapsGumEar plugsTelephone receiver

• Items commonly used by bank robbers to disguise themselves

• DNA can be obtained from the saliva left on the mask or from the sweatband of a baseball cap

Masks and Caps

Chewing Gum• A ring of thieves would steal

cars to use as their “get-a-way” vehicles.

• Gum taken from the ignition switch of the stolen cars matched one of the suspects

• He confessed and led police to the others involved

Bandages• Bank robber covered his

face with bandages to disguise himself

• He threw them away outside the bank

• DNA recovered from the adhesive portion matched the suspect

Why is DNA Testing Valuable?

• can be retrieved from evidentiary stains and tissues

• tests are available

• DNA is unique to you (unless you have an identical twin) and therefore very discriminating

• Your DNA is the same, regardless of the body fluid or tissue from which it is obtained– Therefore, DNA obtained from a semen stain from an

evidentiary item can be compared to that from a suspect’s blood sample

• We can “amplify” very small amounts of DNA for analysis using the Polymerase Chain Reaction (PCR)

DNA Basics

• DNA is a molecule located in the

nucleus of a cell• Every cell in an organism contains

the same DNA• Characteristics of DNA varies

between individuals within a species and between species

What is DNA?

•Figure 9–1  How nucleotides can be linked to form a DNA strand. S designates the sugar component, which is joined with phosphate groups (P) to form the backbone of DNA. Projecting from the backbone are

four bases: A, adenine; G, guanine; T, thymine; and C, cytosine.

DNA basics:• Double-stranded polymer made up

of nucleotides.

• Phosphoric acid and deoxyribose sugar form backbone

• Cytosine always bonds to guanine (C-G)

• Adenine always bonds to thymine (A-T)

• C-G and A-T referred to as base pairs

•Label the DNA molecule shown below.

•BACKBONE

•ADENINE

•THYMINE

• N BONDS

• CYTOSINE

• GUANINE

• Word List: • Cytosine Adenine Thymine Guanine Backbone

• Hydrogen Bonds

What is DNA?•DNA stands for deoxyribonucleic acid and contains genetic information. It is found on chromosomes located in the nucleus of our cells.

DNA Image: http://science.howstuffworks.com/genetic-science/dna-evidence.htm

•What makes up DNA?• The sides or backbone of the DNA molecule are made up of sugar (deoxyribose) and phosphate molecules.

• The rungs that form the middle of the molecule are made up of pairs of nucleotides or nitrogen bases. Adenine (A) pairs with thymine (T), while guanine (G) always pairs with cytosine (C).

• The order of the bases determines the genetic code.

Double

Helix

Identify the complementary strand for the following strand of

DNA:

-C-A-A-T-G-G-A-G-A-

DNA is contained in chromosomes

• Chromosomes contain DNA and associated proteins (which allow the DNA to condense/wind up tightly)

Inside each human cell:

23 pairs of human chromosomes:one from each parent (Karyotype)

What is a chromosome?

•Tightly packed

DNA wrapped

around histone

proteins

Chromosomes, DNA, genes, and nucleotides

• Chromosomes contain genes

• Genes are sequences of DNA nucleotides (1 section of 3 nucleotides code for a specific amino acid (codon), that strings together with other amino acids to make up proteins)

• Chromosomal regions in

between genes contain

variable nucleotide sequences

•Figure 9–3  (a) A string of amino acids composes one of the protein chains of hemoglobin. (b) Substitution of just one amino acid for another

in the protein chain results in sickle-cell hemoglobin.

Genetic variation•Alleles are differences (variation) in a gene within a population of a species

•Genes determine phenotype (physical characteristic) of a structure, molecule, etc.