Cell Reproduction A sea urchin begins life as
Cell Reproduction A sea urchin begins life as a single cell that (a) divides to form two cells, visible by scanning electron microscopy. After four rounds of cell division, (b) there are 16 cells, as seen in this SEM image. After many rounds of cell division, the individual develops into a complex, multicellular organism, as seen in this (c) mature sea urchin. (credit a: modification of work by Evelyn Spiegel, Louisa Howard; credit b: modification of work by Evelyn Spiegel, Louisa Howard; credit c: modification of work by Marco Busdraghi; scale-bar data from Matt Russell)
The Cell Cycle **Orderly set of steps between eukaryotic cell divisions Why do Cells Divide? Growth Reproduction (in single celled organisms) Repair
There are 23 pairs of homologous chromosomes in a female human somatic cell. These chromosomes are viewed within the nucleus (top), removed from a cell in mitosis (right), and arranged according to length (left) in an arrangement called a karyotype. In this image, the chromosomes were exposed to fluorescent stains to distinguish them. (credit: “ 718 Bot”/Wikimedia Commons, National Human Genome Research)
Control of the Cell Cycle G 1 Checkpoint - Check to see if DNA is damaged G 2 Checkpoint - Check to see if DNA is replicated properly M Checkpoint - spindle assembly checkpoint, check for alignment of chromosomes Apoptosis - programmed cell death, if any of the checks fail
Mitosis & Cytokinesis Mitosis - The division of the nucleus that results in identical complete copies of chromosomes packaged into two new nuclei Cytokinesis - The division of the cytoplasm that results in two daughter cells
Interphase • Prophase • Metaphase • Anaphase • Telophase IPMAT
**In plant cells, cytokinesis begins when a new cell wall forms between the two new cells. **In animal cells, the two new cells pinch and pull apart
Cells that are not actively preparing to divide enter an alternate phase called G 0. In some cases, this is a temporary condition until triggered to enter G 1. In other cases, the cell will remain in G 0 permanently.
The cell cycle is controlled at three checkpoints. Integrity of the DNA is assessed at the G 1 checkpoint. Proper chromosome duplication is assessed at the G 2 checkpoint. Attachment of each kinetochore to a spindle fiber is assessed at the M checkpoint.
(a) The role of p 53 is to monitor DNA. If damage is detected, p 53 triggers repair mechanisms. If repairs are unsuccessful, p 53 signals apoptosis. (b) A cell with an abnormal p 53 protein cannot repair damaged DNA and cannot signal apoptosis. Cells with abnormal p 53 can become cancerous. (credit: modification of work by Thierry Soussi)
The Cell Cycle and Cancer neoplasm: abnormal growth of cells benign: non-cancerous malignant: cancerous Cancer: cellular growth disorder that results from the mutation of genes that regulate the cell cycle Cancer cells ●lack differentiation ●have abnormal nuclei ●form tumors ●undergo metastasis & angiogenesis
Mitosis produces 2 daughter cells The two daughter cells contain the exact same number of chromosomes as the original parent cell Daughter cells are DIPLOID
He. La Cells A He. La cell (also Hela or hela cell) is a cell type in an immortal cell line used in scientific research. It is the oldest and most commonly used human cell line. The line was derived from cervical cancer cells taken from Henrietta Lacks, a patient who eventually died of her cancer on October 4, 1951. Article on Henrietta Lacks
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