Chapter 12- The Cell Cycle

-reproduction of cells-division of one cell reproduces an entire organism -on a larger scale, can produce progeny from some multicellular organisms -enables sexually reproducing organisms to develop from a single cell-fertilized egg, or zygote-functions in renewal and repair, replacing cells that die from normal wear and tear- in bone marrow continuously make new blood cells-passing genetic material to offspring is crucial

-the life of cell from time it is formed from a dividing parent cell until its own division into two cells

-most involves distribution of identical genetic material--DNA--to two daughter cells (not sperm and eggs)-duplicates DNA, allocates two copies to opposite ends of cell, and then splits into daughters

-cell's endowment of DNA-prokaryotic is one long DNA; eukaryotic are many DNA molecules

-replication and distribution of so much DNA is manageable becasue DNA molecules are packaged into these -every eukaryotic species has a characteristic number of these in each cell nucleus -somatic cells have 46 in two sets of 23, one set inherited from each parent-reproductive cells (gametes) sperm and eggs have half as many-one set of 23-number varies widely among species

-eukaryotic chromosomes made of this complex of DNA and associated protein molecules -each single chromosome contains one very long, linear DNA molecule that carries several hundred to a few thousand genes, the units that specify an organism's inherited traits -the associated proteins maintain the structure of the chromosome and help control the activity of the genes

-when not dividing, and when preparing for division, chromosome is in the form of long, thin, chromatin fiber-after duplication, chromosomes condense-coil and fold, making shorter and thick

-each duplicated chromosome has two of these-each contain identical DNA molecule and are initially attached by adhesive proteins called cohesions

-adhesive protein that attaches sister chromatids

-In its condensed form, the duplicated chromosome has a narrow "waist" here -specialized region where 2 chromatids are most closely attached--part of chromatid on either side is the arm -later, the chromatids separate and move into two new nuclei, one at each end of cell-each new nucleus receives DNA identical to parent

-division of nucleus

-Division of the cytoplasm -follows mitosis-now there are two cells

-you inherited 46, 23 from each parent; they were combined in nucleus of a single cell when a sperm from your father united with an egg from your mother, forming fertilized egg (zygote) -Mitosis and cytokinesis produced the 200 trillion somatic cells that now make up your body and the same processes continue to generate new cells to replace damaged

-cell division that produces gametes (eggs and sperm)- non-identical daughter cells that have half as many chromosomes as the parent cell-only occurs in gonads -in each generation of humans, meiosis reduces the chromosome number from 46 (two sets) to 23 (one set)-fertilization fuses 2 gametes together and returns the chromosome # to 46

-Mitosis and cytokinesis-shortest part of cell cycle-alternates with interphase