MITOSIS AND CELL CYCLE Flashcards
Role of mitosis
Asexual reproduction/binary fission
Growth (embryogenesis)
Repair injury or replacing cells
Differentiation of stem cells
Role of meiosis
Sexual reproduction
Production of haploids (gametes)
Increases genetic variation
What is the cell cycle
All cells arise from other cells
Cells are always in one of the phases of the cell cycle
Not all cells in multicellular organisms retain the ability to divide
Mitosis in adults
.Neuronal cells once differentiated dont undergo mitosis and stay in the rest position
New neurones are generally not produced in adults
.most tissues in the body are replenished in a similar way to skin tissue where stem cells divide to produce new differentiated cells
.an epidermal stem cell undergoes mitosis to produce a non- replicating epithelial cell and another stem cell to continue genesis
Describe how chromosomes change during the cell cycle
Before a cell can divide it needs to grow and increase the number of sub cellular structures such as ribosomes and mitochondria
The DNA replicates to form two copies of each chromosome
One set of chromosomes is pulled to each end of the cell and the nucleus divides
Finally the cytoplasm and cell membranes divide to form two identical cells
what is a chromosome
a genetic material that has all the features and characteristics of an organism
cycle in more detail
chromosomes shorten and thicken
chromosomes have two identical chromatids due to replication
chromatids move to the equator
attach to individual spindle fibres
spindle fibres contract and centromeres divide
chromosomes move to opposite poles
each pole receives identical copies of each chromosome
nuclear envelope forms around each group of chromosomes at each pole
what is cancer
a disease resulting from cells that break away from an original tumor to form a secondary tumor elsewhere in the body (metastasis)
what is a tumor
a swelling that is made up of cells that continue to divide in an abnormal way
what is metastasis
the spread of tumor forming cells usually through blood stream or lymph nodes to form secondary tumors
what are checkpoint controls
a cells surveillance mechanism which ensures that the cell cycle (hence cell growth) happens only when necessary and correctly
which proteins carry out the checkpoint control
- growth factors
- cyclins- coded for by tumor suppressor genes and proto-oncogenes
sometimes checkpoints are ineffective, what is the effect of this
can cause cancer
two types of mutations
gene
chromosome
what are gene mutations
mutations that affect small regions of DNA, usually one base
occur during DNA replication during mitosis
