DNA Structure Macromolecule – nucleic acid View as a spiral ladder or double helix Composed of nucleotides - deoxyribose sugar, phosphate group, and nitrogenous bases Nitrogenous bases – thymine, adenine, cytosine, & guanine Base pairing A bonds with T and C bonds with G Double strands are held together by hydrogen bonds

Chromosomes Structures in the cell that contain genetic information Passed on from one generation to the next Made up of chromatin Humans body cells contain 46

KARYOTYPE

Intro to Genetics Normally all cells have 2 sets of chromosomes; one from ma and one from pa. Humans have 23 pair or 46 chromosomes. 46 is our diploid (2N) number of chromosomes. Meiosis Process by which gametes (sex cells) receive only one set of chromosomes. 23 is our haploid (N) number of chromosomes. Sperm and eggs are haploid. They only have 23 chromosomes.

Intro to Genetics Each chromosome we receive from a parent has a corresponding one we receive from the other parent. (ma and pa). They each contain the same genes (sections of DNA covering a particular trait). These chromosomes are said to be homologous.

CELL GROWTH and DIVISION Examples Cells must multiply to: *replace damaged or dead cells. *Repair wounds *Body Growth

CELL GROWTH An increase in size due to the production of more cells Growth is controlled by the amounts of food, oxygen, and water that enter the cell. And waste products that leave the cell

RATES OF CELL GROWTH Different types of cells divide at different rates E-coli can double every 30 minutes

CONTROLS ON CELL GROWTH Cells in the heart and nervous system rarely divide. Cells in the skin and digestive system divide rapidly throughout life. Cell growth and division can be turned on and off When an injury occurs cell division increases near the injury. When the healing process is complete cell division stops.

LIFE SPANS OF DIFFERENT HUMAN BODY CELLS Brain Cells 30-50 years Liver Cells 200 days Skin Cells 20 days Stomach Cells 2 days Muscle Cells mitosis does not occur. You are born with all the muscle cells you will have.

Uncontrolled Cell Growth Cancer: A disorder in which some cells have lost the ability to control their own growth rate.

Cell Division Example Mitosis: The process by which the nucleus of the cell is divided into 2 nuclei, each with the same number of chromosomes as the parent cell. Cytokinesis: The process by which the cytoplasm divides, forming 2 distinct cells

The Cell Cycle The period of time from the beginning of one mitosis to the beginning of the next 1 The cell grows 2 prepares for division 3 Divides to form 2 daughter cells

The Cell Cycle G1, S, and G2 represent the 3 phases of Interphase G1=Growth S=DNA Synthesis G2=Growth

The cell Cycle M= Mitosis and Cytokinesis The Nuclei and cell divides to form 2 new ones

Interphase The period between Cell Divisions G1: Cell growth S: DNA Replication occurs in this phase G2: The synthesis of organelles required for cell division

4 Phases of Mitosis Prophase Metaphase Anaphase Telophase

Prophase 1st phase of mitosis The longest phase 50-60% of mitosis Chromosomes become visible Centrioles separate to opposite sides of the cell Spindle develops Nuclear envolope breaks down

Metaphase Shortest phase (few minutes) Chromosomes line up along the center of the cell Spindles connect from the centromeres to the chromosomes

Anaphase 3rd phase of mitosis Begins when sister chromatids split Sister chromatids separate to oppposite ends of the cell Anaphase ends when movement stops

Telophase The final phase of mitosis The nuclear envelope reforms The spindle breaks apart Mitosis is complete Cell division is not

Cytokinesis Division of the cytoplasm into 2 cells Animal Cells: The Cell membrane pinches inward Plant Cells: a cell plate forms to separate the cells (It becomes the cell wall)

E-coli, salmonella and other bacteria can reproduce quickly E-coli, salmonella and other bacteria can reproduce quickly. Lets say 30 minutes. If you eat contaminated food and it contains one cell how many will you have after 4 hours? 5 hours?

½ 2 1hr 4 1 +1/2 8 2 16 2+1/2 32 3 64 3 + ½ 128 4 256 4 +1/2 512 5 1024