Meiosis, Mendel-The Principles of Inheritance
Meiosis, Mendel-The Principles of Inheritance BIOL 121N
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Trace Mante MD
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This 8 page Class Notes was uploaded by Dominick Ramos on Tuesday October 27, 2015. The Class Notes belongs to BIOL 121N at Old Dominion University taught by DOUGLAS J MILLS in Fall 2015. Since its upload, it has received 9 views. For similar materials see GENERAL BIOLOGY I in Biological Sciences at Old Dominion University.
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Date Created: 10/27/15
BiollZlNMeiosis Meiosis o Meiotic cell division enables haploid 1N gamete production and thus sexual reproduction o Gametes sex cells egg and sperm Errors during meiosis can cause aneuploidy resulting in genetic disorders or miscarriage o Occurs in reproductive organs 0 Sex cells divide by meiotic cell division to produce geneticallyvariable haploid 1N cells that develop into gametes that enable sexual reproduction I Occurs in gonads paired sex organs of humans I Occurs in flowers of flowering plants 0 Meiotic cell division maintains a constant chromosome number across generations 0 Mom has 46 chromosomes dad has 46 chromosomes meiosis guarantees that you also have 46 chromosomes 0 Aneuploidy abnormal chromosome number typically is lethal in humans 0 Increases genetic variation in sexuallyreproducing populations due to the 0 Formation of geneticallyvariable gametes sex cells 0 Production of offspring progeny that differ genetically from each parent Our bodies require Meiosis and Mitosis MitosisProduces the supply of new cells necessary for growth renewal repair and defense Meiosisproduces the geneticallyvariable gametes sex cells necessary for sexual reproduction l Parent celll cmagma MElD S39S 39 39 v r k 39Chmmnsnme q Chromosome 39 Pl phlgge IEPIIE iml39l I replication Pmphasel w I 39 as I 39 139quot5 Homologous 4quot I chromosome Heplicated chromosome quot l Pa r r I a Metaphaso I 39 H Metapheeell 3 fr 394 2 2 a I k 39339 2 Anaphxase 2 1 539 1 Anepneee I J 2 39 39 Telo haeel 39ll39elophase I R I 5 gg r p r a lHaplcnd IVE V 3 lA I Daughter Huh quot I quotT 39 oelieol39 5 39 iquot l llTlEll SiSll 39I 2n 2n 39 39 39 MEIOEISM Daughter cells Fquot n 3939 n I fut 39n39 quotWu of mitosis Daughter calla of meiosis i SUMMARY A Occur duling inlenphase before 0 dinning i ntarphasa before meiosis lbagine quotWIFEINN milosis begins Number m one In uulnu panphaae melapnege we each lnelii h ag prapnnee manganese snapmsemu dlulemne enephaaa em lelnphasie Holman synepsie or Does not occur Occurs winning mimosa I along Will39I crossing over homologous lbaiumn mnsiel39er chloma tide rasull39ingi chiaernaila oh mmmm mEa 39L39 quot 39 39 Qu mhb39nI z39 f 39 quot Number of Tmquot 39 439 quot quot 39 T FnIr39 39 rrmfarir39ingl mm mamquot can menlicel ID in parem ngll mm paremgem gangliaally alllerem Im the parent and gone 39 cell and from each miner 39ompcsmu Role In Ihe Enema munloellullal adult to arise from a f n animal may zygote pmdumoeiia lnr glam wepeil and inuodum genetic varianilily among the 9am and in 5mm speomuamual lepmduclion Cmnll39 quot55 Biol121NMeiosis AN VIERWDEW IMF MMEHKEDTJIC CELL DMSHEDN EDNA REPU CAWEEDN PMCEDES 39 E39J nc klf l ll 53533533521 quotl ili lgl 51 lmE Ill HED E HC CELL ID quoti 39 l SHEEN Hmal gausbalrmonmmoaomea HOWDLOGOU E CHROWOSOHES THE FOUR INTER CTIlNG 39quotd39quot3939l l39f39f vquot HOMOLOGS CHROMATIDS FORM A TETRAD Ll A DllPLDlID 2N CELL HAS TWO H H COMPLETE SETS OF GHROMSOMES Mmmuspms c replica v Homologous val o renllmu mmomae 39 AFTER DNA REIP39LIGATION DNA ouAREPucAnow r l THEREAREFOURGOMPLETE gggggggL OGGURSBEFORE m g l ymmumwh SETSOECHEoMpsomESIN Repmmunm MEIo39rIo CELL olvmsmu Lill im THE NUGLEUS if i l II x IIljdlomol gosis l x V EHWOFW39 x supan ww 1 quot cHRomosoME 39 39 1 FROM MOM CHROMDSOME 951mmm91 1 FROM DAD AFTER DNlA lREPLICATIDNl r lt gt 7 swarm lt I quot 39 THE TWO SIlSTER HApLom GnMETES 1N v l HAPLOID GAMETES 1N 39 r r l I I I l clIiRomTIle REmAIN csraz zmsaa izalzs man an we CENTROMERE Meiosis l 1 Crossing over occurs between all of the homologous chromosomes The spindle separates each pair of homologous chromosomes and delivers each pair of sister chromatids to opposite ends of the cell a The 2 maternal sister chromatids separate from the 2 paternal chromatids during anaphase of meiosis 3 Two cells are formed a Each cell contains either the 2 maternal sister chromatids or the 2 paternal sister chromatids for chromosomes 122 and i XXin females ii XX or YY in males Crossing Over Crossing over genetic recombination occurs between homologous chromosomes during prophase of meiosis 0 During crossing over new combinations of maternal and paternal alleles are formed on the homologous chromosomes to create quotrecombinant chromosomes Meiosis ll 1 Each pair of sister chromatids is separated a During anaphase II the spindle delivers each sister chromatid to opposite ends ofthe cell 2 Four haploid 1N cells are formed 3 The haploid 1N cells can develop into gametes if they receive the proper signals BiollZlNMeiosis Nondisjunction can result in genetic disorders Aneuploidy abnormal chromosome number in our gametes is due to the failure of the o Homologous chromosomes to separate during meiosis 0 Sister chromatids to separate during meiosis Meiotic cell division creates genetically diverse gametes o All possible combinations of our maternal and paternal chromosomes can enter into each gamete during meiotic cell division 0 Each gamete can have any of the 223 84 million possible combinations of our maternal and paternal chromosomes WE lNHERIT OUR ANCESTORS CHROMO SOMES MDM S EGG HIS mourns EGG HAS CHROMOSDME I FRQM BHRDMIJSOMIE 1l FFIDM mama LITTLEWOITITH GRAN DPA LIITLEWDIUTH 0quot 1quot uquot cHRomosoME a 1 lt0 DIWS SPERM HA5 MD39S 5FE H HAS BHRBMDS IME l F iR DM an EH DSDME Il FROM GRJINIIIIA MILLS GRANIIPA MILLS COMBINATIONS OF GRANDPARENTE COPY OF CHROMDSOME 71 I I YOU CAN IMHERIT ANY OF THESE FOUR BiollZlNMeiosis TODAY S STUDY GUIDE QUESTIONS WHERE DOES MEIOTIC CELL DIVISION OCCUR IN WOMEN MEN FLOWERING PLANTS WHICH TYPE OF CELL DIVISION IS NECESSARY TO FORM HAPLOID 1N GAMETES MAINTAIN A CONSTANT NUMBER OF CHROMOSOM ES ACROSS GENERATIONS PRODUCE GENETICALLYVARIABLE HAPLOID 1N CELLS FROM DIPLOID 2N CELLS ENABLE SEXUAL REPRODUCTION HOW DOES NONDISJUNCTION DURING MEIOTIC CELL DIVISION RESULT IN GENETIC DISORDERS DO MOST ANEUPLOID GAMETES SEX CELLS FORMED DURING MEIOSIS SELF DESTRUCT ARE THE CELLS OF MISCARRIED FETUSES FREQUENTLY ANEUPLOID DURING MEIOTIC CELL DIVISION WHEN DOES THE SPINDLE SEPARATE HOMOLOGOUS CHROMOSOMES SISTER CHROMATIDS DOES MEIOTIC CELL DIVISION GENERATE GENETIC VARIATION IN POPULATIONS HOW ARE NEW ALLELE COMBINATIONS GENERATED ON EACH HOMOLOGOUS CHROMOSOME DURING PROPHASE 1 OF MEIOSIS 1 DOES EACH GAMETE PRODUCED THEORETICALLY HAVE AN EQUAL PROBABILITY OF CONTAINING ANY POSSIBLE COMBINATION OF OUR MATERNAL AND PATERNAL CHROMOSOMES WHY IS GENETIC VARIATION BENEFICIAL FOR POPULATIONS CAN EACH CHROMOSOME IN THE HAPLOID 1N GAMETES YOU PRODUCE HAVE ALLELES FROM BOTH OF YOUR PARENTS WHY CAN YOUR GENOME CONTAIN CHROMOSOMES FROM EACH OF YOUR GRANDPARENTS BiollZlNMendelian Genetics Mendel s Monohvbrid Crossing Experiment 0 Allowed Mendel to investigate the inheritance pattern of one trait o The two parents must have identical traits except for the trait under investigation for example flower color 0 This is necessary to control for the impact of other traits on the pattern of inheritance for the trait under investigation Mendel s Procedure Conducting a controlled monohybrid crossing experiment 1 Demonstrate that each parental line breeds true for the trait under investigation 2 Cross the parents to produce the F1 generation of monohybrid Pp offspring 3 Analyze the phenotype ratios of the F1 generation offspring a The ratio purple white flowers will provide insight into the pattern of inheritance for the trait under investigation 4 Cross the F1 generation monohybrid Pp offspring with one another to produce the F2 generation 5 Analyze the phenotype ratios of the F2 generation offspring The importance of Replication Mendel replicated his monohybrid crossing experiments extensively to increase the probability of detecting biologicallyrelevant patterns in the data Replication is required to analyze experimental data statistically Different parental traits do not mix in the offspring Offspring a mixture of the different traits they inherited from each parent 0 Each parent transmit genetic info in discrete units of heredity called genes that code for a specific trait giploid Individuals have two alleles 0 One allele is inherited from the female parent 0 One allele is inherited from the male parent One modification to Mendel s rule human males have one copy of each gene on the X chromosome and on the Y chromosome Mendel s Law of Segregation During meiotic cell division the two alleles of each gene separate and each allele enters into a different gamete BiollZlNMendelian Genetics 0 This is due to only one of the two homologous chromosomes entering into each gamete during meiotic cell division Mendel s Law of Allele Separationonly one of the two alleles for each gene enters into each gamete Recessive traits remain hidden for a generation TH PARENT BR EEPS l quot quot l39 a TRUE FOR WlRlINMLED Hp lwrical amend u39riln kl lad seed 6 SEEDS i G mwlli Parental Pl seeds THIS PARENT BREEDS TRUE FOlR SMOOTH l39ailllen i Parentallll lpllanls quotl 397 quot yr l I39 THE WRINKLED SEED TRAIT rs ABSENI W F set 5 Maturatium HIDDEN H IN THE HETEROZYGDUS F1 GENERA an WITH THE quot 55 GENOTYPE g leuth A Il RECE55IlVE 39TRAIlTquot THAT REMAINS HlIDDEN IN RESL39LIs39 l l39I seeds Eram l39l plij A A a REAPPEAR IHN ITS OFFSPRING Dominant and recessive phenotypes In some heterozygotes only one of the two inherited alleles is expressed in the phenotype o The expressed allele causes a dominant phenotype o The hidden allele causes a recessive phenotype Mendel s testcross experiment This experiment enabled Mendel to determine the genotype of an individual with a dominant phenotype o The genotype could be homozygous dominant PP or heterozygous Pp o This individual must be crossed with a homozygous recessive pp individual to determine its genotype BiollZlNMendelian Genetics Achondroplasia The A allele causes the dominant dwarf phenotype the a allele causes the recessive wildtype phenotype typical height How can homozygous recessive aa parents can have a child with Achondroplasia Aa The probability of mutations in gametes increases with age Most cases are due to a mutation converting the a allele to the quotAquot allele in the sperm of older fathers Some mutations in the fibroblast growth factor receptor 3 FGFR3 gene result in reduced bone length TODAY S STUDY GUIDE QUESTIONS DESCRIBE EACH STEP OF MENDEL S MONOHYBRID CROSSING EXPERIMENT WHY DID MENDEL REPLICATE HIS MONOHYBRID CROSSING EXPERIMENTS WHICH PRINCIPLES OF INHERITANCE EMERGED FROM MENDEL S IMPRESSIVE SERIES OF MONOHYBRID CROSSING EXPERIMENTS DESCRIBE THE PURPOSE OF THE TESTCROSS WHY IS THE TESTCROSS IMPORTANT FOR ANIMAL AND CROP BREEDING EXPERIMENTS WHY ARE THERE TWO ALLELES FOR EACH GENE IN THE NUCLEI OF OUR DIPLOID 2N CELLS WHICH CELL DIVISION PROCESS ALLOWS DIPLOID 2N CELLS TO PRODUCE HAPLOID 1N GAMETES BiollZlNMendelian Genetics ACCORDING TO MENDEL S LAW OF SEGREGATION DO ONE OR BOTH ALLELES OF EACH GENE ENTER INTO EACH GAMETE DURING MEIOTIC CELL DIVISION WHY DON T THE DIFFERENT TRAITS OF EACH PARENT MIX IN THEIR OFFSPRING PROPOSE A MOLECULAR HYPOTHESIS TO ACCOUNT FOR WHY ONLY ONE OF THE TWO ALLELES OF A GENE IS EXPRESSED IN THE PHENOTYPE OF SOME HETEROZYGOTES IS THE ACHONDROPLASIA PHENOTYPE RECESSIVE OR DOMINANT HOW CAN WILDTYPE PARENTS OF TYPICAL HEIGHT HAVE A CHILD WITH THE ACHONDROPLASIA PHENOTYPE THERE ARE NO INDIVIDUALS WHO ARE HOMOZYGOUS DOMINANT AA FOR THE ALLELE THAT CAUSES ACHONDROPLASIA WHY