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Chapter 5: Cell Division
Important terms and concept
1. Haploid – Cell with single set of chromosome (n)
2. Diploid – Cell with complete sets of chromosomes (2n)
Prophase Chromosomes start to appear and condense as 2 identical chromatids
Nuclear membrane disintegrate and nucleolus disappear
Centrioles move apart to opposite sides Spindle fibre begins to form
Metaphase Chromosomes move to cell’s equator Chromosomes line up at cell’s equator with centromeres
attached to spindle fibre Each chromatid faces its own pole
Anaphase Chromosomes divide into two Each sister chromatid separate and move to opposite
poles When the chromatids reached its own pole, they become
independent chromosomes
Telophase There are now 2 sets of chromosomes, one at each pole Chromosomes become thread-like structures Spindle fibre disappear Nuclear membrane begins to form around both sets of
Telophase I Chromosomes reached its own pole Each pole has haploid chromosome set Spindle fibre disappear Nuclear membrane and nucleolus reform Cytokinesis begins
3. Meiosis II is the same as mitosis
4. Importance of meiosis
a) Allow trait inheritance in offspring
b) Maintain same number of chromosomes in each generation
c) Ensure production of haploid gametes in sexual reproduction
d) Produce genetic variation
Comparison between Meiosis I and Meiosis II
Meiosis I Meiosis IISimilarities
1. Consists of 4 stages, ie. prophase, metaphase, anaphase & telophase2. Involves division of nucleus and cytoplasm
DifferencesYes, at Prophase I Synapsis No
Yes, at Prophase I Crossing over No
In metaphase I, paired homologous chromosomes / bivalent / tetrad line up at equator
Metaphase
In metaphase II, sister chromatids line up at equator
In anaphase I, homologous chromosomes separate and move to opposite side
Anaphase I
In anaphase II, sister chromatids separate and move to opposite side
2 different daughter cells ( n )Number of daughter cells