Wee 2 Notes
Wee 2 Notes BSCI - 30156 - 002
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BSCI - 30156 - 002
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This 3 page Class Notes was uploaded by Jessica Brown on Monday February 1, 2016. The Class Notes belongs to BSCI - 30156 - 002 at Kent State University taught by Chi-hua Groff (P) in Fall 2015. Since its upload, it has received 42 views. For similar materials see ELEMENTS OF GENETICS in Biological Sciences at Kent State University.
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Date Created: 02/01/16
Genetics Week 2 Nemonic for remembering the phases of Mitosis and Meiosis Put My Answer There (prophase, metaphase, anaphase, telophase) Meiosis Genetic purpose is to produce four haploid cells (n) that are unique and different from the parent cells as well as the other haploid cells These happen through the germline Meiosis starts at the zygote. o Fusing of parent cells (2n) End result of meiosis is germ cells (sperm and eggs) This is how genetic diversity exists o Due to crossing over (only occurs in meiosis NOT mitosis) Prophase 1 Pairing of sister chromatids. Homologous chromatids. o They are referred to as tetrads ( 4 DNA sequences lined up. 2 are from the mother and 2 are from the father) Points of contact occur on the chromatids o This physical interaction is the beginning of crossing over Metaphase 1 Tetrads will line up at the plate. Not connected at the centromere like they are in mitosis Anaphase 1 The cell separates into 2 separate cells Crossing over has occurred Telophase 1 Separating is completed o Two cells distinctly different from parent cells and each other (thanks to crossing over) Prophase 2 Poles organize but there is no interaction with the chromatids Metaphase 2 Line up and separate—no crossing over. Anaphase 2 Cell pulls apart Telophase 2 4 cells result—each cell different and unique The second half of meiosis is called reduction division Y chromosome has an SRY locus The SRY locus is what turns on the male pathway Extra Y chromosome caused by sperm having an extra Y. Causes the sex chromosome to be XYY o Monosomy— Having one chromosome—you can live with this ONLY if it’s on the sex chromosomes o Polysomy—multiple or more chromosomes. This is not lethal but causes many syndromes. Nondisjunction Chromosomes fail to separate o Results in gametes and zygotes with an abnormal chromosome number Aneuploidy: Variation in chromosome number. Involves there being 1+ chromosomes. o This is a result of errors in meiosis Which is a result of nondisjunction o Aneuploidy in anaphase 1 of meiosis—daughter cell gains too much info, one has not enough Since meiosis produces 4 cells then two of these cells would have too much information and two of them would have not enough. Autosomal Inheritance Human autosomal traits are located on non sex chromosomes They can be inherited in two ways o Autosomal recessive (rr) Only homozygous recessive individuals exhibit affected phenotype Males and females are equally affected and both have an equal chance of passing on the trait if they are carriers May skip generations Because of people who carry o Autosomal dominant (Rr or RR) Homozygous dominant (RR) and heterozygous dominant (Rr) will exhibit the trait. They have an affected phenotype. Males and females are equally affected Does NOT skip generations Mendelian inheritance only applies to autosomal chromosomes. Gregor Mendel Worked with pea plants Used monohybrid cross Discovered that how a single trait on a single loci is passed from parent to offspring Parental Generation (P1) ((TT) Tall plant) X ((tt) Short Plant) F1 Generation. All Tall (Tt) Self cross with f1 to get f2 F2 Generation. ¼ short and ¾ tall This showed the DNA does not go away—it returns through the carrier (Tt) Punnet Square: Visual representation of particular genes in gametes and how they combine in offspring
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