Chapter 11 - DNa introduction

Forensics Uses DNA evidence has been used to investigate crimes, establish paternity, and identify victims of war and large- scale disasters Science and the Law: the Implications of DNA Profiling New York State to Exonerate Innocent Prisoners Using DNA The Smoking Gun, 9/11 DNA Evidence Revisited DNA Paternity Test – Worldwide Increase

Background information Body consists of 60 trillion cells –Most of these cells contain a nucleus  The exception = Mature red blood cells –Each nucleus contains the genetic material, or the directions, to make us who we are The genetic material is found in structures called chromosomes

Background information Chromosomes are composed of little segments called genes –The gene is the fundamental unit of heredity  Holds instruction for the body cells to make proteins that determine everything from hair color to our susceptibility to disease Each gene is composed of a specific sequence of DNA

Dna DNA stands for  deoxyribonucleic acid –Blueprint, or directions, for all living things –Universal – found in every living thing In humans, DNA is in the form of a double helix, or spiral ladder  Shape was discovered by James Watson and Francis Crick in 1953

Dna components DNA is made up of primary units called nucleotides –Each nucleotide is composed of three pieces  Sugar (deoxyribose)  Phosphate group  Nitrogenous base –Four different bases: Adenine, Guanine, Thymine, Cytosine

DNA shape The sugar and the phosphate group create the backbone of the molecule –This is the sides of the ladder The bases are the rungs of the ladder

Base pairing rule Each base matches up with one other specific base = base pairing rules  Adenine will always bind to thymine, and vice versa  Cytosine will always bind to guanine, and vice versa Each DNA strand contains over 1 million base pairs –It is the order of bases that dictate your traits

Types of Dna Nuclear Found in the nucleus Constitutes 23 pairs of chromosomes inherited from both parents Each cell contains only one nuclei Mitochondrial Found in the cytoplasm Is inherited only from mother Each cell contains hundreds of thousands of mitochondria Can be found in skeletal remains Nuclear DNA is present in the head of the sperm. Mitochondrial DNA is present in the tail. At conception, the head of the sperm enters the egg and unites with the nucleus. The tail falls off, losing the father’s mitochondrial DNA

Nuclear DNA Mitochondrial DNA

Non-Coding Regions 3 percent of the human DNA sequences code for proteins  97 percent is non-coding and is repetitive; repeating the same sequence over and over 50 percent of the human genome had interspersed repetitive sequences