Oct.26, 2016 Biology Lecture 18 Ability of organisms to reproduce best distinguishes things from nonliving things. Continuity of life is based of reproduction of cells, or cell division In unicellular organisms, division of one cell reproduces the entire organism Multicellular organisms depend on cell division for Development from a fertilized cell Growth Repair Cell division has allowed us to have more cells which allows us to grow and develop more. If we hurt ourselves, we can rapidly divide to replace the cells that have been injured. Cell division is integral part of cycle, the life of a cell from formation to its own division. Cell division results in genetically identical daughter cells Most cell division results in daughter cells with identical genetic information DNA Cell grows splits in half cell grows splits in half etc. A special type of division produces non identical daughter cells only occurs in (gametes, or sperm and egg cells, or spores). Cellular organization of the genetic material All the DNA in a cell constitutes the cells genome************* A genome can consist of a single dna molecule (common in prokaryotic cells) or a number of dna molecules (Common in eukaryotic cells) Dna molecules in a eukaryotic cell are packaged into chromosomes Genome consists of all dna in a cell Every eukaryotic species has a characteristic number of chromosomes in each cell nucleus, for humans it is 46. Somatic cells non reproductive cells; have 2 sets of chromosomes in most plants and animals. We have 2 sets of 23 chromosomes Gametes (Reproductive cells: sperm and eggs and spores) have half as many chromosomes as somatic cells. They have 23 chromosomes. Eukaryotic chromosomes consist of Chromatin, a complex of DNA and protein that condenses during cell division. It gets spooled up.