Continuing Life Cells must divide to continue life Asexual reproduction occurs when an organism simply buds or divides to make another copy of itself (binary fission) The division of body (somatic) cells is called mitosis

Organisms that reproduce asexually: hydra, bacteria, some molds, plants, a species of lizard Other organisms reproduce sexually: Two cells combine to form a new organism human male karyotype Meiosis reduces the number of chromosomes in sex cells to half the norm…so human sex cells have 23 (half of 46!).

DNA Code of Life All living things (except some viruses) use DNA to carry their genetic info.

Structure 4 bases: adenine, thymine, cytosine, guanine Rosalind Franklin took X-ray pictures of DNA and saw it was a double helix James Watson and Francis Crick figured out the structure of DNA (1953)

Chromosomes contain DNA (deoxyribonucleic acid) which contains genes. Genes “code” for what you look like, how you develop, etc. There are different versions of genes called alleles.

Dominant and Recessive Some traits are determined by only one set of genes (pairs). If one gene in the pair is dominant, it covers up the recessive one. EXAMPLE: in pea plants, tall is dominant over short. So, a plant with a tall gene and a short gene will be tall. Which plants will be short?

Cloning-A How-to Guide Cloning- can be used to produce offspring that are genetically identical to their parent. Uses cells from a donor organism. The cell’s DNA is then inserted into an empty egg. The egg is then given a mild shock or chemical “bath”. The egg may then begin dividing and can be implanted into a female to carry.

Cloning-Is it ethical? Scientific ethics- “the study of the impact of technology and science on society” As the debate continues about whether humans or anything should be cloned, think about your own opinion on the subject. Do we really need to be able to clone humans? What about farm animals? Why is cloning NOT the answer to the endangered species problem?