cells and genes

• the nucleus of all human cells contain 23 pairs of chromosomes

• these chromosomes are made of DNA

• the DNA contains information in the form of genes

• each gene contains a particular characteristic

• genes controls the activities inside the cell

• genes code for production of proteins inside the cell

• these proteins have an effect on function of cells and are often enzymes

• there are approximately 20,000 different genes in a human and all human cells process all 20,000 genes

• in a developing red blood cell the gene for producing haemoglobin (a protein) would be switched on

• in a developing bone cell this same gene is switched off

type of tissues

• epithelial tissue - this is a tissue that either covers or lines an organ for example - blood vessels or the lining of gut

• epithelial tissues forms the inner surface of glads that secrete substances such as sweat and digestive enzymes

• simple epithelial : squamous, cuboid, columnar, ciliated

• muscle tissues : skeletal muscle - movement (attached to the bone)

• cardiac muscle - in the heart

• smooth muscle - in the walls of artery,gut and the bladder

• nervous tissue : transmit nerve impulses to the brain and they are the body’s communication system

• connective tissue : any supporting tissue in an organism

• consists of a non-living supporting matrix ; often containing protein fibers

• living cells are present within in matrix

• these cells often produce the matrix

• includes : bones, cartilages, tendons, ligaments, blood, areolar tissue, adipose tissue

• tendons are attached muscles to the bone

• ligaments also attach to the bone

• areolar tissue holds things together eg: skin and muscle in a chicken

• adipose is a fatty tissue