Rabu, 28 Desember 2011

materi mitosis dan meiosis in english, sma kelas xii, semester 1

Difference Between Mitosis and Meiosis

Difference Between Mitosis and Meiosis

Mitosis vs Meiosis
Meiosis and Mitosis describe cell division in eukaryotic cells when the chromosome separates.
In mitosis chromosomes separates and form into two identical sets of daughter nuclei, and it is followed by cytokinesis (division of cytoplasm). Basically, in mitosis the mother cell divides into two daughter cells which are genetically identical to each other and to the parent cell.
Phases of mitosis include:
mitosis
1. Interface -where cell prepares for cell division and it also includes three other phases such as G1 (growth), S (synthesis), and G2 (second gap)
2. Prophase – formation of centrosomes, condensation of chromatin
3. Prometaphase- degradation of the nuclear membrane, attachment of microtubules to kinetochores
4. Metaphase- alignment of chromosomes at the metaphase plate
5. Early anaphase- shortening of kinetochore microtubules
6. Telophase- de-condensation of chromosomes and surrounded by nuclear membranes, formation of cleavage furrow.
7. Cytokinesis- division of cytoplasm
Meiosis is a reductional cell division where the number of chromosomes is divided into half. Gametes formations occur in animal cell and meiosis is necessary for sexual reproduction which occurs in eukaryotes. Meiosis influence stable sexual reproduction by halving of ploidy or chromosome count. Without meiosis the fertilization would result in zygote with twice the number of the parent.

Phases of meiosis include:
meiosis
1. Meiosis I – separation of homologous chromosomes and production of two haploid cells (23 chromosomes, N in humans)
2. Prophase I – pairing of homologous chromosome pair and recombination (crossing over) occurs
3. Metaphase I – Homologous pairs move along the metaphase plate, kinetochore microtubules from both centrioles attach to the homologous chromosomes align along an equatorial plane.
4. Anaphase I – shortening of microtubules, pulling of chromosomes toward opposing poles, forming two haploid sets
5. Telophase I – arrival of chromosomes to the poles with each daughter cell containing half the number of chromosomes
6. Meiosis II – second part of the meiotic process with the production of four haploid cells from the two haploid cells

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