Sec. 5.2 – Asexual Reproduction (c) McGraw Hill Ryerson 2007

(c) McGraw Hill Ryerson 2007 5.2 Asexual Reproduction Produces clones = identical genetic copies of the parent Many organisms naturally form clones by asexual reproduction Also used in agriculture & research to copy desired organisms, tissues and genes See pages 168 - 175 (c) McGraw Hill Ryerson 2007

(c) McGraw Hill Ryerson 2007 Types of Asexual Reproduction Binary fission - single cell organisms splitting into identical copies (c) McGraw Hill Ryerson 2007

(c) McGraw Hill Ryerson 2007 Budding - a new organism develops from an outgrowth (“bud”) due to cell division at one particular site. (c) McGraw Hill Ryerson 2007

(c) McGraw Hill Ryerson 2007 Fragmentation - part of an organism breaks off due to injury, and the part grows into a clone of the parent (c) McGraw Hill Ryerson 2007

Vegetative reproduction - special cells in plants that develop into structures (ex. stolons, rhizomes, etc.) that form new plants Spore formation - some bacteria, micro-organisms and fungi can form spores - single cells that can grow into a whole new organism

Advantages to Asexual Reproduction Only need one parent No time needed to find mate Less energy required because no mate to find No gametes (egg/sperm) needed Can create a large number of offspring quickly Large colonies can out-compete other organisms for resources Large colonies may survive changing conditions & predation better (c) McGraw Hill Ryerson 2007

Disadvantages to Asexual Reproduction Offspring are clones would all inherit bad traits would all be susceptible to same diseases no variation to allow survival if conditions change dramatically if colonies are close together, they could compete for resources (c) McGraw Hill Ryerson 2007

Human Assisted Cloning A.k.a. Artificial selection Used to produce desired traits within an organism We use all asexual reproductive methods (c) McGraw Hill Ryerson 2007 See pages 176 - 177

(c) McGraw Hill Ryerson 2007 Examples: Reproductive cloning - used to produce a genetic duplicate of an existing or dead organism. Steps involved: Remove nucleus from an egg cell A mammary gland cell is removed from an adult female Electricity fuses mammary and egg cell Fused cell begins dividing Dividing embryo is inserted into surrogate mother (c) McGraw Hill Ryerson 2007

(c) McGraw Hill Ryerson 2007

Issues Only about 10% of clones survive Surviving clones can be abnormally large & have higher risk of infection and cancer Ex) Dolly only lived 6 years and died of lung disease (c) McGraw Hill Ryerson 2007

Therapeutic cloning - purpose is to correct health problems Uses stem cells - cells that can become different types of cells Stem cells can replace cells damaged from injuries or disease Controversial because the best stem cells are embryotic However, many diseases are now treated with adult stem cells Diabetes, spinal injuries, Parkinson’s disease, cancer See pages 177 - 178

Autologous Stem Cell Rescue Take the Section 5.2 Quiz