Genetics (BIOL 3000) Lecture 1/2 notes
Genetics (BIOL 3000) Lecture 1/2 notes BIOL3000
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This 6 page Class Notes was uploaded by Kennedy Finister on Saturday February 6, 2016. The Class Notes belongs to BIOL3000 at Auburn University taught by Rita Graze in Fall 2015. Since its upload, it has received 187 views.
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Date Created: 02/06/16
Genetics Lecture 1, 2 January 13th/ 15th/ 2016 What is Genetics? • The branch of biology that deals with heredity & the expression of the inherited traits in individuals o Includes variation in inherited traits in populations & genetic differences at the species level • How traits are passed down & expressed o Example: hair color Areas Of Genetics • Transmission genetics o Mode of inheritance, as well as segregation, assortment & mapping o Mendel era v Where are genes located? v How are genes physically passed down? v How do genes sort? • Cytogenetics o Chromosomal biology, including structure, function, variability & disease • Molecular Genetics o Gene structure & function, including replication & regulation v How are genes expressed? v How is DNA replicated? v How are proteins made? • Population Genetics o Genetic makeup & dynamics over space & time (ie evolution) of entire populations v Human genome o How is it structured/interpreted o What's in it? • Genomics o Content organization, structure & function of entire genomes Why Genetics? • Know more about your family & ancestors • Blame your Neanderthal ancestors for stuff • Personalization of health & medicine • Understand new discoveries Earliest Theories of Heredity • Spontaneous generation 1 Genetics Lecture 1, 2, 3 January 13, 2016 o The idea that animals are spontaneously generated abiotically from certain materials § Examples: • Insects from dirt • Mice are around wheat in your barn, they must generate from the wheat • Preformationism o The adult form exists inside the egg or sperm as a tiny homunculus (a supposed microscopic but fully formed human being in form which a fetus was formerly believed to develop) which simply grows to full adult size during development • Pangenesis o The idea (theory) that small, exact copies of body parts (pangenes) are transported are transported by the bloodstream to the reproductive organs & are assembled into the gametes • Epigenesis o New structures, such as tissues & organs, can appear during developments that are not present at the time of original formation. The first expression of the idea that phenotypes (observable characteristics/traits) themselves are not only the potential of producing them is inherited • Biogenesis o Living things come from other living things via reproduction • Germ-‐Plasm Theory o Cells in the reproductive organs carry a complete set of genetic information that is passed to the egg/sperm. That is there are germ cell (sperm & eggs) & somatic (non reproductive) cells. Information is inherited in the sperm in the germ cells & not from somatic cells 2 Genetics Lecture 1, 2 January 13th/ 15th/ 2016 Mitosis • Cell division, always regulated • All cells carry same DNA (genetically identical) • Can be unregulated (uncontrolled growth) o Divides when they shouldn’t & fail to make sure daughter cells are genetically identical o Cancer or birth defect DNA all located in nucleus ß most important Genetic Information is housed in chromosomes (DNA on a protein scaffold = chromosomes) • Each DNA molecule = chromatid • 2 sister chromatids attached = dyad 1 sister chromatid = monad • “X” = 2 DNA molecules attached at centromere • Monad à duplication à dyad à mitosis à daughter chromosomes • 23 pairs of chromosomes • 46 total chromosomes o autosomes & sex chromosomes • n = # of chromosomes in a single set [23 in humans] • 2n = # of chromosomes considering both chromosome sets [46 for humans] Homologues • have the same length, centromere location & genes. They’re just different versions (mom & dad) Mitosis • somatic cell division • 2 cells from 1 cell • Zygote (diploid 2n) à mitosis à adult (diploid 2n) • Morphology o Results from when they (the cells) divide, where & how much they divide mitotically through division • Basis o Genetic information has to be copied o Moved to daughter cells evenly o Divide into two cells • Discovered by Walter Flemming by looking at salamanders • 5 stages 1. prophase 2. prometaphase 3. metaphase 3 Genetics Lecture 1, 2, 3 January 13, 2016 4. anaphase 5. telophase/cytokinesis Prophase • form organized chromosomes/microtubules to move microtubules • chromosomes condense organize • asters appear o looks like mickey mouse Prometaphase • one nucleus to two by breaking down nuclear membrane • asters move two either side & turn into spindles o microtubules extend to nuclear region • spindles form from microtubules organizing centers (MTOCs) ß “stars” o microtubules extend/shorten from here • microtubules connect to chromosomes at this stage at the kinetochore • spindle microtubes come from both sides of kinetochore o attachment allows them to move Metaphase • Chromosomes line up on the metaphase plate • Spindle is fully formed • Spindle checkpoint o Basics § Detect error & initiate fix o In Depth § Make sure everything is correct, no errors in chromosomes 4 Genetics Lecture 1, 2 January 13th/ 15th/ 2016 o Done through tension. Tugs on both sides to see if they’re connected to kinetochore (think of it as a chinese finger toy) o If there’s no connection in a set of sister chromatids they’ll look to fix it § Sister chromatids connected by cohesion Anaphase • Sister chromatids are pulled apart to opposite poles o Pulled by shortening the microtubules Telophase/Cytokenesis • Nuclear membrane reforms (one for each daughter cells) & spindle breaks down • Chromosomes relax • Cytokinesis happens after telophase o Where the cells actually divide o (looks like pinching play dough) Cell Cycle • mitosis is a very small part • most cells are in G0 & the rest divide in interphase (3 stages) 1. G1 2. s-‐phase 3. G2 • When are sister chromatids formed? o S-‐phase, when DNA is replicated or Synthesized • G1 o Before replication § 2 homologus chromosomes § genetically distinct • (same type of information but not identical) • G2 o Post replication § Getting ready for mitosis § 2 chromosomes are identical & produced by DNA replication 5 Genetics Lecture 1, 2, 3 January 13, 2016 • G0 o Non dividing cells • Checkpoints o Spindle assembly checkpoint in mitosis o G0 what cells are dividing Vs Not § Fake checkpoint o DNA damage § Between G1 & S-‐phase § Needed because they’re about to duplicate & its hard to duplicate chromosomes if they’re damaged o DNA damage & replication § Making sure everything has been replicated oCheck points keep cell cycle regulated Cancer happens because checkpoints fail • Get out of G0 when they’re not supposed to, leading to rapid growth • Checkpoints breakdown & chromatids aren’t identical 6
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