Chapter 8 - Chapter 8 Cellular Reproduction Cells from...

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Chapter 8 – Cellular Reproduction: Cells from Cells Life With & Without Sex: Rain Forest Rescue o Saving the Hawaiian Bellflower Went extinct in the wild in 2003 Tried to promote sexual reproduction – fertilization through the union of a sperm and an egg by – by transferring pollen - Failed Labs since then have created many through asexual reproduction – production of offspring by a single parent o Cell Division = heart of organismal reproduction Characteristic of living things (reproduction) Cell reproduction underlies process of sexual reproduction Asexual and sexual reproduction among plants and animals WHAT CELL REPRODUCTION ACCOMPLISHES o Cell division (reproduction) – two daughter cells genetically identical to each other result from the original parent cell Chromosomes – the structures that contain most of the organism’s DNA - Parent cell duplicates these before splitting - One identical set is distributed to each of the daughter cells o Roles of Cell Division Reproduction Replace damaged or lost cells Growth o Asexual Reproduction – reproduction that does not involve fertilization of an egg by a sperm Offspring inherit all of their chromosomes from a single parent Examples: - Starfish grows new individuals off fragments
- Clippings of lettuce grows new stalks Parent and offspring have identical genes Mitosis – the type of cell division responsible for asexual reproduction and for the growth and maintenance of multicellular organisms o Sexual Reproduction – reproduction that requires fertilization of an egg by a sperm Meiosis – special type of cell division involved in the production of egg and sperm cells - Occurs in reproductive organs THE CELL CYCLE AND MITOSIS o Chromosomes Almost all genes located on chromosomes in cell nucleus (eukaryotic) - Except mitochondria / chloroplasts Lead players in cell division Eukaryotic Chromosomes o The Basics e/chromosome = long DNA molecule (thousands of genes) number of chromosomes in eukaryotic cell = depends on species chromatin – a combination of DNA and protein molecules - material that makes up chromosomes - protein molecules = organize chromatin / control gene activity o Long Fibers Fibers of DNA in one cell is VERY long Preparing to divide - Chromatin fibers coil up compact chromosomes When cell is not dividing
- Chromosomes are too thin to be seen in light micrograph o DNA Packing - DNA in chromosome is packed into elaborate, multilevel system of coil / folding Allows long molecules of DNA to fit inside tiny cell nucleus Histones – small proteins found only in eukaryotes - DNA associated = crucial to DNA packing Level 1: histones attach to the DNA - Histones attach to DNA double helix (beads on a string) - Nucleosome (bead) – DNA wound around histone molecules o DNA Packing & Functionality Preparing to divide - Chromosomes pack further beaded string wrapped into tight helical fiber -

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