Mitosis and Meiosis and the Cell Cycle

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ACCESS TO HIGHER EDUCATION

HUMAN BIOLOGY

Explaining the role of mitosis & meiosis

IN GROWTH AND REPRODUCTION

Table of Content
Page Number
Cell division1
Why do we need cell division?1
Chromosomes1
What is a chromosome?1
The Cell Cycle 2

Process of Mitosis 3

What is Mitosis?3
Stages of Mitosis 3
Interphase3
Prophase4
Prometaphase5
Metaphase5
Anaphase6
Telophase7
Cytokinesis 8
Process of Mitosis 9
What is Meiosis? 9
Meiosis I10
Meiosis II11-12
Break Down of Meiosis 13
Summary of Mitosis and Meiosis14 -16
Glossary
Reference

Process of Mitosis

What is Mitosis?
Mitosis is a nuclear division as well as cytokinesis, during prophase, prometaphase, metaphase, anaphase and telophase; it produces two identical daughter cells. Interphase is technically not part of the mitosis but it encompasses the stages of G1, S, and G2 of the cell cycle.

Stages of Mitosis

Interphase

Here the cell is busy in metabolic activity and it preparing for the next stages of mitosis. As the chromosomes are not clearly discerned in the nucleus, but the nucleolus may be visible. The cell could even contain a pair of centrioles which are the organized sited for microtubules.

Before the cells being to divide the chromosomes are replicated; ATP is synthesized, which provides energy to the cell division, the organelles are also replicated and protein are then made. The following are all replicated in this stage, DNA, histones and centrioles. The replication of cell organelles such as mitochondria only occurs in the cytoplasm.

Prophase

Prophase is when the chromatin in the nucleus starts to condense and starting to become more visible under the light of a microscope as chromosomes. The nucleus then disappears, and centrioles start to move to opposite ends of the cell and fibres begin to extend from the centromeres, some of the fibres cross the cell to produce mitotic spindle. The DNA is copied of each chromosome to form two chromatids. The chromosomes start to condense, becoming fatter and shorter, starting to become more visible under LM. The nuclear envelope starts to break down, the chromosomes start to lie freely in the cytoplasm, the centrioles start to move to opposite sides of the cell, beginning to form tublin fibres across it which is called spindle, the centrioles produce the spindles and the fibres begin to extend to the equator of the cell. The chromosomes attach themselves to the spindles.

Prometaphase

In prometaphase the nuclear membrane begins to dissolve, this the beginning of prometaphase. The protein that are attached to the centromeres start to crate the kinetochores, the microtubules attach themselves to the kinetochores and the chromosomes begin to move.

Metaphase

Metaphase is where the spindle fibres starts to align the chromosomes in the middles of the cell nucleus, this is called the metaphase plate. This is an important part for the next stage, so when the chromosomes separate the new nucleus will be able to receive one copy of each. As the chromosomes line up at the equator the spindle fibres start to become attach themselves to the centromere of the chromosome.

Anaphase

Anaphase is when the paired chromosomes separate at the kinetochores and start to move to the opposite sides of the cell. The motion result is both the combination of the kinetochore movement as well the spindle microtubules, and going through the physical interaction of the polar microtubules. As the spindle fibres begin to contract, the chromosomes start to split and the pair of sister’s chromatids are then separated and are dragged to opposite ends of the poles in a ‘V’ shape. ATP is need when a...
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