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Flashcards in Mitosis Deck (26):

What is mitosis?

Eukaryotic cells have a well defined cell cycle of growth and division. The length of the cell varies ending with mitosis. Each phase involves specific activities and varies in length from one organism to another.


What are the stages of the cell cycle?

G1 - Growth Phase 1, cells prepare for DNA replication.
S - synthesis, DNA replication occurs
G2 - Growth Phase 2, short gap before mitosis
M - mitosis, nuclear division relatively short


What check chromosome for mutations?

Proof reading enzymes


What is mitosis affected by?

The availability of nutrients.


What might happen to chromosomes with mutations picked up by the proof reading enzymes?

They may undergo 'suicide' if there are harmful mutations this is known as apoptosis.


How long does it take for bacterial cells to complete a cycle?

20 minutes


Muscle cells never complete a cell cycle what is this called?

Terminal differentiation


What can uncontrolled cell division by mitosis cause?



Define mitosis?

Process by which a nucleus divides into two, each with an identical set of chromosomes. They are genetically identical.


What are the four stages of mitosis?

Prophase, metaphase, anaphase and telophase.


What happens before mitosis?



Define interphase?

Stages G1, S and G, it's the period of cell growth, cells prepare for nuclear division, genetic material is copied and checked for errors, new organelles and proteins are made.


What occurs after mitosis?



What occurs in interphase?

The cell is engaged in metabolic activity. The DNA duplicates during this phase to prepare for mitosis. Chromosomes are not clearly discerned in the nucleus although a dark spot may be visible called the nucleolus.


What occurs in prophase?

Chromatin in the nucleus begins to condense and becomes visible in the light microscope as chromosomes. The nuclear membrane breaks down and the chromosomes can be seen to consist of two chromatids. These X shaped structures move along the spindle to the opposite poles of the cell.


What happens in metaphase?

Chromosomes align along the middle of the spindle. This line is referred to as the equator. This organisation helps to ensure that in the next phase, when the chromosomes are separated, each new nucleus will receive a copy of each chromosome.


What happens in anaphase?

The chromatids separate at the the centromere and move to opposite ends of the cell. They are pulled by the spindle. The separated chromatids can now be referred to as new chromosomes.


What happens in telophase?

New membranes form around the daughter nuclei while the chromosomes disperse and are no longer visible under a light microscope.


What happens in cytokinesis?

The cell physically divides in two.


What occurs during G1?

Protein synthesis cell 'grows'. Most organelles produced. Volume of cytoplasm increases, cell differentiation occurs, length of this stage depends on the internal and external factors. If a cell is not going to divide again it stays in this stage. DNA content = 20.


What occurs during S?

DNA replicates, this must occur if mitosis is to take place. The cell enters this stage only if cell division is to follow. DNA content = 40.


What occurs during G2?

Short gap before mitosis. Cytoskeleton of cell breaks down and the protein microtuble components begin to reassemble into spindle fibres. DNA content = 40


What does DNA content = in cytokinesis?

DNA content = 20


What happens if the treatment for cancer is too strong?

It would kill off too many healthy cells which can lead to death.


Define tumour?

A tumour is a group of undifferentiated abnormal cells. These can get larger and compress with tissues and use nutrients from the body. These cells can break off to form secondary tumours in other parts of the body.


How is cancer caused?

Carcinogens such as tar and uv radiation causes mutations in the DNA of the cell. These mutations are changes in the nucleotide sequence of DNA this may happen via insertion, deletion or the order may change.