Mitosis & MeiosisSBI 3U

Ms.ZafarNovember 29th, 2012

Mitosis The cells of a multicellular organism

are formed through mitosis Differentiation responsible for

differences among cells Takes place in somatic cells

Mitosis Diploid number: number indicating

the complete set of chromosomes

Mitosis & Cancer Cancer: a group of diseases characterized

by abnormal cell division Different from normal cells in 2 ways: -uncontrolled division -continue to divide and pile up on each other

creating a tumour

Mitosis & Cancer Malignant vs. benign Metastasis dangerous. Can move

through body and invade new tissues

Mitosis & Cancer Treatment options:

-Radiation therapy – directed at specific sites within the body to kill cancer cells-Chemotherapy – drugs-Immunotherapy – using the body’s own natural defences

Meiosis

Meiosis Meiosis is a special type of cell

division necessary for sexual reproduction in eukaryotes

Meiosis prevents the doubling of chromosomes when gametes unite

Chromosome Number & Structure 23 pairs of homologous

chromosomes 2 in a pair – 1 one from mother and 1

from father Maternal set vs. Paternal set Each homolog carries the same

hereditary traits as its partner

Chromosome Number & Structure Info for specific traits stored as

genes Each gene is located at a locus Alleles: different forms of genes

Chromosome Number & Structure # of chromosomes in each gamete is one-half of the

diploid number called the haploid number Fertilization results in the joining of 2 haploid gametes

to make a single diploid cell called the zygote

Stages of Meiosis Meiosis occurs only in reproductive

tissues 2 major divisions – Meiosis I and

Meiosis II

Meiosis I – Prophase I Genetic material has been replicated before

Meiotic division Chromosomes become visible Synapsis: homologous chromosomes come

together Tetrad: 4 chromatids together Chiasmata and crossing over

Metaphase I Tetrads have moved to the equator

Anaphase I Chromatids do not split – instead the

chromosomes move apart from each other

Telophase I Chromosomes condense slightly and

a nuclear membrane forms 2 daughter cells result half the

number of chromosomes Reduction division