Cellular Reproduction

Cell Division What would happen if cells stopped dividing? Could your skin function in protection? Would wounds heal or your body grow?

Two Types of Cell Division Asexual Simple division of one cell (mitosis) Does not involve fertilization “Daughter” cells are genetically identical Sexual Requires 2 unique cells Zygote is genetically distinct

Cell Division Chromosomes are structures that become visible during division Chromosomes have the DNA of the cell

DNA Packing

Cell Division Chromosomes must replicate before division occurs

Cell Division Some new terms: Chromatin: combination of DNA and protein fibers (not visible) Sister chromatids: copied chromosome Centromere: where the sister chromatids are joined

The Cell Cycle

The Mitotic Phase Four phases Prophase Metaphase Anaphase Telophase Cytokinesis occurs at the end of telophase

Things to Know Describe what happens in each phase of mitosis. Identify key structures that are assembled or disassembled.

Cytokinesis: Animals and Plants

Control of Cell Division Cancer: cells with severely deranged cell cycles Malignant tumor: lump produced from cancer cells Metastasis: spreading of cancer cells beyond original site

Control of Cell Division Normal cells are in your body are controlled mitotically as to when and where division occurs Cell Cycle Control System

Chemotherapy Vinblastine First obtained from periwinkle plant Rainforest of Madagascar Taxol Yew tree

Sexual Reproduction Mitosis produces two daughter cells that are identical Reproduction between two individuals are similar but not exact…why?

Sexual Reproduction Offspring receive genetic inheritance from two parents Sperm and egg cells each carry half the number of chromosomes Fertilization is the combining of egg and sperm genetics (and thus the two parents) Meiosis is the production of sperm and egg cells (specialized cells only used for reproduction)

Meiosis Terms Somatic cell: typical body cell Gamete: sperm or egg cell Homologous chromosomes: Each somatic cell contains two of each chromosome (one from mom; one from dad)

Meiosis Terms Karyotype: arrangement of homologous chromosomes (biggest to smallest) Diploid: part of the life cycle that contains two homologous sets of chromosomes

Meiosis Terms Diploid: part of the life cycle that contains two homologous sets of chromosomes Haploid: part of the life cycle that contains a single chromosome set Zygote: the product of fertilization (diploid)

How Meiosis Halves Chromosome Number

Genetic Diversity Why is it important that meiosis produce a high degree of genetic diversity in its final product? Three main methods of increasing genetic diversity Crossing Over Independent Assortment Random fertilization

Crossing Over

Random Fertilization

When Meiosis Goes Wrong Errors in the meiotic stages can produce sperm and egg cells with an abnormal number of chromosomes

When Meiosis Goes Wrong

Down Syndrome Trisomy 21 1 out of 700 children

Down Syndrome What does this graph show us? Can you explain the results of this graph?

Meiotic Errors and Evolution Many plants are known to be polyploidy Remember what haploid and diploid is? Since plants can self- fertilize, polyploidy can be quite common Hugo de Vries and his primroses

Meiotic Errors and Evolution What about animals? Very rare since most animals can’t self- fertilize The red viscacha rat from Argentina possibility?