Genetics is that branch of biology concerned with

Genetics is that branch of biology concerned with heredity and variation

• The DNA, in the help of proteins, becomes organized into chromosomes found in the nucleus of the cell • All cells have DNA and RNA. • Viruses only have DNA or RNA surrounded by a protein sheath

• The most primitive cells alive today are the bacteria the Monarans. They have all the qualities of life but do not have membrane bound organelles • Viruses are also primitive but are not considered alive since they do not have all the qualities of life • Viruses as noncellular particles reproduce in a host using the lytic or lysogenic cycle.

• a viruses virulence, or ability to cause disease can be “hidden” in the • lysogenic cycle (virus attacks without apparent harm) or • lytic (almost immediate breakdown of a cell) • When a cell is infected by the virus, the cell’s DNA has been altered by the phage DNA • An enzyme is then produced to break open the infected cell

What are the characteristics of life? • able to organize simple chemicals into complex molecules; • requiring a constant input of energy; • an ability to respond to the environment • DNA and RNA • Has a cell membrane • Reproduces • Growth • homeostasis

• All other kinds of cells that have a nucleus (including fungi, plants, protista, and animals) are referred to as eukaryotes

• The cells of a multicellular organism seldom look alike or carry out identical tasks. The cells are differentiated to perform specific functions (sometimes referred to as a "division of labor" • And most have varying types and numbers of organelles.

Mitochondria Ribosomes golgi apparatus E. R

nucleus centrioles

Cell membrane in distilled water Cell membrane in salt water

Low power High power 4 X x Low field of view = 100 X High filed of view