Cellular basis of reproduction and inheritance
• Organisms have life cycles
– adult to adult
• Cellular reproduction
– growth by cell division
Prokaryotes reproduce by binary fission
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Eukaryotic cell cycle and mitosis
• More complex
• Large amounts of DNA arranged in chromosomes
– chromosomes visible only during cell division
– chromosomes exist as a diffuse mass called chromatin at other
times
• Number of chromosomes differ between species
– 46 in humans, 4 in fruit fly.
Chromosomes duplicate with each cell division
• Duplicated sister chromatids
attached at centromere
2
The cell cycle
Mitosis and cytokinesis
3
Mitosis and cytokinesis (cont’d)
Cytokinesis differs for plant and animal cells
4
Factors affecting cell division
• anchorage dependence
– need to be in contact with a surface
• density dependent inhibition
– form single layer in cell culture
• growth factor portein stimulates cell division
Density dependent
inhibition
growth factors
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Growth factors
signal the cellcycle control
system
Cancer as a result of improper functioning of the
cell-cycle control system
• Tumors
– benign and malignant
• Metastasis of cancer cells
• Cancers named according to the originating organ
– Carcinomas – external or internal linings (skin and intestine)
– Sarcomas – supporting tissues (bone and muscle)
– Leukemias and Lymphomas – blood forming tissues
• Cancers cells not affected by density dependent inhibition
• Treatments target cell division
– radiation and chemotherapy
6
Meiosis
Meiosis with crossing over
7
Independent orientation of chromosomes and
random fertilization lead to much variation
2n
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