Chromosomes, Cell Division and Meiosis

DIPLOID CELLS- Normal body/ Somatic cells contain 46 chromosomes: Half from both mother and father (2 x 23)- They are described as diploid - 2 out of he 46 are sex chromosomes and determine your sex     Females: A pair of X chromosomes XX     Males: An X and Y chromosome XY- The other 44 chromosomes are autosomes- These autosomes can be grouped into 22 pairs that are homologousHomologous chromosomes have the same:LengthCentromere position Same gene loci

KARYOTYPES- illustrates the shape, size and number of chromosomes in an individual - Profile of a person's chromosomes-  Arranged from Largest to smallest

HAPLOID CELLS- Cells that contain one set of chromosomes- Human haploid cells have 23 chromosomes- Sex cells/ gametes

HOW WE BEGAN Zygote- single cell Diploid 2N Formed in fertilisation  Egg and sperm are haploid(N) containing one set of chromosomes each

MEIOSIS- Nuclear division that occurs when gametes are produced   - TWO divisions = 4 haploid cells (23 chromosomes) chromosomes replicate to become double stranded  These homologous chromosomes line up along the cell equator One double stranded chromosome from each pair moves to each end of the cell Two cells are formed Double stranded chromosomes line up at equator Chromatids separate and move to opposite ends of the cell

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