Mitosis

Jamie Z 2024-11-05

Learning Goals

Describe the process of fertilization
Describe the difference between asexual and sexual reproduction
Explain advantages and disadvantages of asexual and sexual reproduction
Compare the roles of mitosis & meiosis (Mitosis is for growth, repair and asexual reproduction; meiosis is solely for the production of gametes.)
Contrast the process of mitosis and meiosis (consider number of cells produced, diploid/haploid daughter cells, number of phases) .

The process of combining the male gamete, or sperm with the female gamete, or ovum. The product of fertilisation is a cell called a zygote

Does not involve sex cells or fertilisation, only one parent is required, unlike sexual reproduction
As a result the offspring are genetically identical to the parent and each other

The production of new organisms by the combination of genetic information of two individuals of different sexes.
In most species the genetic information is carried on chromosomes in the nucleus of the reproductive cells called gametes (sperm and egg) which then fuse together to form a diploid zygote (2 copies of chromosomes)

	Sexual Reproduction	Asexual Reproduction
Advantages	- High genetic diversity - Better adaptation to changing environment - Will not be wiped out by a single change to the environment - Facilitates adaptation to the environment	- Saves Energy - No time needed to find a mate
Disadvantages	- Energy costly - Time required to find a mate	- Low genetic variability - Can be wiped out by a single change to the environment - Adaptation to environment is difficult

Animals and plants grow by increasing the number of cells they are made of. To do this, body cells go through a process called the cell cycle
The cell cycle is made of two stages: Interphase and mitosis
After a cell has gone through the cycle, the parent cell produces two identical daughter cells

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Growth and development - An increase in the number of body cells enables organisms to grow larger in size
Repair and replacement - New cells produced by the cell cycle can be used to replace old damaged cells in a organism so that they can continue to function
Asexual Reproduction - Some organisms use the cell cycle to produce offspring

When a cell duplicates via the cell cycle, 90% of its time is spend in interphase
It is the phase of the cell cycle in which a cell copies its DNA to prepare for mitosis
Each chromosome and sub cellular structure are duplicated through the process of DNA replication
A cell is unable to enter mitosis until every chromosome has been duplicated
As a result of DNA replication, at the end of interphase the cell has double the normal number of chromosomes in its nucleus.

Nucleus breaks down, allowing the duplicated chromosomes to be split between daughter cells in later phases.
During prophase the CENTROSOMES also appear (brown cylinders on the image).
The two centrosomes form the poles of the mitotic spindle fibres, which segregates the chromosomes (in further stages) into two separate daughter cells.

All the chromosomes align across the middle (metaphase plate) of the parent cell.

The duplicated chromosome are pulled apart from one another, to opposite ends of the cell.
Each sister chromatid is held together by a centromere. This allows the spindle fibres to pull the chromatids apart into two identical cells.

In telophase, the cell nucleus is reformed around the two new sister cells which BOTH contain IDENTICAL GENETIC INFORMATION TO THE PARENT CELL.
In cytokinesis the cytoplasm of the cell is split, cleaving the cell into 2 new DIPLOID daughter cells.