DNA

What is DNA? Contains all genetic information of the entire organism Located in the nucleus of all cells (with a few exceptions!) mature red blood cells have no nucleus sex cells have half the amount of genetic information (haploid) A “full set” in humans is 46 chromosomes Made up of 23 pairs (diploid)

But not in all animals! Organism # of Chromosome Pairs Human 23 Drosophila (fruit fly) 4 E.coli (bacteria) Mosquito 3 Fly Frog 18 Cat 19 Chimpanzee 24 Horse 32 Dog 39 Onion 8 Peanut 12

DNA spends most of its time in a long string called chromatin During cell division, chromatin coils up tightly to form chromosomes

the section of DNA that codes for a protein is called a gene

DNA -> RNA -> Protein (made of amino acid)

DNA Structure DNA is made of nucleotides composed of 3 parts DNA: 5 carbon sugar: deoxyribose one nitrogenous base (4 possible options!) phosphate group DNA: Deoxyribo- Nucleic acid

There are two types of nitrogenous bases: 1. Purines -Adenine (A) and Guanine (G) -2 fused rings 2. Pyrimidines -Cytosine (C) and Thymine (T) -only one ring Adenine ALWAYS bonds with thymine Guanine ALWAYS bonds with cytosine -this is called complimentary base pairing

DNA looks like a twisted ladder This arrangement is called a double helix

Alternating sugar and phosphates make up the backbone (the “rails” of the ladder) Bases make up the “rungs” and are held together by weak hydrogen bonds