MEIOSIS.

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Meiosis is a special form of cell division.

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Presentation transcript:

MEIOSIS

Structure of Chromosome

Diploid Vs. Haploid Diploid - two sets of chromosomes Haploid - one set of chromosomes Diploid cells (2n or 2 sets of chromosomes) are made into haploid (1n or 1 set chromosomes) during meiosis Examples of diploid cells: almost all your cells! Most plant & animal cells are diploid (2n) Examples of haploid cells: gametes, egg & sperm (n)

How Many Homologous Chromosomes? Homologous pairs carry genes controlling the same inherited traits. Humans have 23 pairs of homologous chromosomes. a. 22 pairs of autosomes b. 1 pair of sex chromosomes

Sex Chromosomes XX chromosome - female XY chromosome - male

Homologous Chromosomes Each organism that is produced via sexual reproduction has 2 copies of autosomes, one comes from each parent Homologous chromosomes (Homo=same) chromosomes that are the same size & shape; carry genes for the same traits

History of Life

Review Mitosis

Meiosis Meiosis: the form of cell division where sex cells are produced (gametes). Purpose: to produce sex cells (gametes) for sexual reproduction Sex cells (sperm or egg) have half the # of chromosomes as a normal body cell

Diploid to Haploid

Spermatogenesis & Oogenesis

Fertilization n= 23 2n = 46 zygote egg The fusion of a sperm and egg to form a zygote. n= 23 egg sperm n = 23 2n = 46 zygote

Question: A cell containing 20 chromosomes (diploid) at the beginning of meiosis would, at its completion, produce cells containing how many chromosomes? ANSWER = 10 chromosomes (haploid) Animation http://www.johnkyrk.com/mitosis.html

Comparison Mitosis Meiosis