mitosis & meiosis
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Mitosis & Meiosis. SBI 3U Ms.Zafar November 29 th , 2012. Mitosis. The cells of a multicellular organism are formed through mitosis Differentiation responsible for differences among cells Takes place in somatic cells. Mitosis. - PowerPoint PPT PresentationTRANSCRIPT
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