Chromosomes, Cell Division and Meiosis

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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 homologous

Homologous chromosomes have the same:

Length

Centromere 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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