Biology 97 Lecture 3 Class Notes
Biology 97 Lecture 3 Class Notes 61860
Irvine Valley College
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This 3 page Class Notes was uploaded by Idda Colcol on Monday August 29, 2016. The Class Notes belongs to 61860 at Irvine Valley College taught by Amy McWhorter in Fall 2016. Since its upload, it has received 27 views. For similar materials see Genetics and Evolutionary Biology in Biology at Irvine Valley College.
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Date Created: 08/29/16
Bio 97 (#61860): Lecture 3 Class Notes (Intro Powerpoint Slides 53-63 & Mendel Powerpoint Slides 1-24) I. Spermatogenesis vs. Oogenesis A. in oogenesis, still have germ cells (stem cells) during fetal development B. all cells are arrested in meiosis I, prophase I 1. these cells are called primary oocytes C. secondary oocyte is frozen in meiosis II, metaphase II, until sperm comes in contact D. ﬁrst polar body can’t be fertilized, has 2c E. after 2 rounds of meiosis, we only end up with 1 egg and 3 polar bodies II. The Origins of Genetic Variation A. new combinations of genes as a result of independent assortment, random fertilization, and recombination III.Independent Assortment of Chromosomes A. independent assortment - different alleles are randomly distributed 1. chromosome pairs align differently of each other in metaphase of meiosis I 2. different combinations of alleles occur when gametes are formed a) 2^23 - combination of alleles lining up IV. Random Fertilization A. One egg is randomly fertilized by one sperm 1. egg is not more or less likely to be attracted to certain sperm 2. sperm is equipped with different enzymes 3. egg has various barriers so not all sperm can go through 4. fertilization membrane: shakes off all other sperm so only one sperm can penetrate through V. Crossing Over A. crossing over - genetic exchange in material that involves breaking one maternal and one paternal chromosome B. DNA can be broken and rejoined with opposite alignment C. missing of one paternal and one maternal 1. gives variation to expression of alleles 2. process happens three-dimensionally VI. When Meiosis Goes Awry in Humans A. non-disjunction - usually incorrect separation B. aneuploidy - genome is partly changed VII.How Accidents During Meiosis Alter Chromosome Number A. to disjoin - to separate B. non-disjunction - failing to separate, staying together VIII.Nondisjunction in Meiosis I or II A. n+1 - full set plus one extra chromosome B. fails to separate sister chromatids during meiosis II IX. Trisomy A. this can occur for all chromosomes B. nondisjunction has same ratiﬁer all chromosomes C. 21,18, etc - can get through fertilization but all others are lethal D. monosomy (sex n chromosome) - Turner syndrome MENDEL POWERPOINT 2 I. Mendel’s First Law: The Principle of Segregation II. Gregor Mendel - Father of Genetics A. Augustinian monk, mid-1800s III.Gregor Mendel and Laws of Inheritance A. Used garden peas because they had distinctive traits that could be carried from one generation to the next IV. Secrets of Mendel’s Success A. plants self-pollinate, self-fertilize B. kept very accurate records of offspring V. Mendel Set-Up Experiments to Answer… A. offspring is hybrid, regardless of phenotype B. when hybrids reproduced, would revert to parent phenotypes VI. Pisum Sativum: Garden Pea A. Mendel chose garden pea because it has different variants 1. 7 variants B. ability of self-pollination can be removed by taking away male-anther producing structures to cross-pollinate VII.Procedure of Mendel’s Experiment A. P: parental B. F1: ﬁrst ﬁlial, can produce offspring C. F2: second ﬁlial VIII.rocedure of Mendel’s Experiments A. F1 monohybrid - hybrid/mixture for one characteristic (trait) 1. always resembled one parent B. biggest success: quantiﬁed data of offspring 1. dominant: one that appeared solely and highest frequently IX. What we learned from Mendel’s monohybrid crosses A. there is something passed on from parent to offspring B. organisms have phenotype possibility of dominant or recessive 1. dominant is visible C. pair must be cut in half during gamete formation 1. Principle of Segregation D. random fertilization 1. any gamete has equal chance of fertilizing other gametes regardless of dominant/ recessive X. More nomenclature A. no such thing as heterozygous dominant or heterozygous recessive B. heterozygous - dominant phenotype C. phenotypes are not limited to what you can see with make eye but also at molecular level 1. size of proteins XI. Punnett Square A. 1:2:1 ratio - look at genotypic ratio B. for every gene there are 2 alleles C. fertilization is random D. 4 fertilization events can take place with equal proportions XII.Using a Testcross to Determine an Unknown Genotype A. between unknown and known phenotype B. dominant phenotype - unknown genotype because it can be homozygous or heterozygous C. we know one allele: D (dominant), but not second D. known individual - homozygous recessive
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