Cellular Reproduction

• Genetic information is found in cell DNA nucleus
• Chromatin: molecules of DNA and proteins (histones) that make up the chromosomes. Looks like one large clump
• Chromosome: A threadlike structure of DNA that carries genetic information through groupings of chromatin (condensed, in tiny compact groups)
• proteins (histones) pack DNA together from chromosomes to chromatin
• ploidy: chromosome # that is characteristic with a specific species (only with somatic cells)
• a somatic cell is a cell that is not a germ cell and is found in animals and humans
• humans have 46 chromosomes
• chromatins have more space between nucleosomes
• DNA is wrapped around protein (histones) and they're all linked together. 1 of these makes a nucleosome, which is the proteins DNA
• gametes are sex/germ line cells: egg and sperm
• somatic cells are nonsex cells. Duplication amount depends on the species
• egg + sperm = 2 copies of each chromosome with 1 copy from each parent
• humans have 22 nonsex autosome pairs, and a single pair of sex chromosomes (X and Y)
• human cells start from diploid cells and undergo meiosis to produce haploid cells
• human diploid cells = 2 sets of each chromosome, 1 copy from each parent
• homologous/homologs carry the same genes at the same location
• each chromosome has only 1 copy: haploid (23 chromosomes)
• in 2n, n/N is ploidy
• autosomes determine biological sex
• paired chromosomes are homologous
• homologous/homologs (the genes within themselves) must have the same shape and size (with different bends to them basically)
• karyotype is the number of chromosomes in a cell and the arrangement of the chromosomes
• genes are sections of DNA containing instructions of protein-making
• alleles are different versions of the same gene found in at a locus (location). 'Options' (such as red vs brown hair, black vs blue eyes)
• albinism is when there's no pigment or melanin for hair, eye, skin color. May cause impairments to vision
• centromere's connect the chromatids of a chromosome. They can be anywhere along the chromatid
• sister chromatids or bivalents are replicated chromosomes
• mitosis is asexual cellular division that maintains normal # of chromosomes after division
• meiosis is sexual cell division that produces gametes with half the number of previous chromosome, causing variation since 2n=46, n=23
• cell cycle = cell life cycle
• cell cycle phases: interphase, mitosis, cytokinesis
• mitosis phases are prophase, metaphase, anaphase, and telophase
• interphase is the longest phase and where DNA replication occurs
• prophase is when

  • chromatin condenses into x-shapes chromosomes (held together by centromere)
  • centrioles duplicate (animal cells)
  • spindle fibers form from centrioles and attach to centromeres
  • nuclear membrane begins breaking up
• metaphase is when

  • spindle fibers align chromosomes to equator of cell
  • nuclear membrane utterly decimated
  • centrioles migrate to 'poles' of cell (opposite ends to each other, can be any orientation)
• anaphase is when

  • centromeres divide and spindle fibers shorten, pulling apart sister chromatids
  • chromosomes now move close to centrioles and face each other on opposite ends of the cell
• telophase is when

  • now that chromosomes are on opposite ends to each other, a cell furrow develops at equator, ready to split the cell
  • nuclear membrane for each respective new cell begins to reform
  • DNA starts uncondensing
  • spindle fibers are broken up
  • final phase of mitosis
• cytokinesis is post-mitosis

  • cell furrow continues until two cells identical to the original cell are created
  • each cell can now enter G1 of interphase, ready to be duplicated once more
• mitosis is necessary for organisms to make accurate copies to replace dead/damaged cells or for the growth of an organism. It's how hydra, bacteria, yeast, etc reproduces
• mitosis and cytokinesis in plant cells:

  • no centrioles, but spindle fibers still form
  • instead of a cell furrow, a membrane called a cell plate forms between the two daughter nuclei and extends to form new cell wall