CM 6 Meiosis Punnett Squares Genetic research into 9 000 year old remains Identity by descendent IBD Adult woman 30 40 yo and infant 7 000 6 800 BCE Found in 1934 in Germany Genetic research determined the infant is fourth or fifth degree relation identity by descent tracts Great great great grandmother to the boy Phenotypic variants in woman s genome determined she had dark skin dark straight hair and blue eyes Undergraduate Research at MSU Reminders HW3 due next Tuesday by midnight Do your iClicker attendance Group CER Feb 10 in class Attendance required unless excused absence with documentation Genetics exam Feb 12 In class must bring photo ID any official ID is fine Do not arrive late you will not be provided any additional time 4x6 notecard allowed front and back Share accommodation letters with me if you have not already done so Plan for today Mitosis review Meiosis Punnett squares Mitosis M phase Prophas e Chromosomes are condensed and replicated Metapha se Sister chromatids align along the cell plate Anaphas e Sister chromatids separate from one another Telophas e Chromatids have moved to separate sides of the cell and new membrane has begun to form Mitosis refresh Metaphase Anaphase G1 Diploid Prophase Telophase Cytokinesis Diploid Mitosis Beginning to Ending Diploid Triploid Tetraploid Diploid Triploid Tetraploid The amount of genetic material stays the same Ploidy remains the same What is the purpose of mitosis Discuss In which cells does mitosis occur A Sex Cells B Somatic Cells C Both Meiosis Process by which gametes are produced by sexually reproducing organisms and the number of chromosomes is reduced by half Produced by specialized cells called germ cells aka Sex cells that are found within the reproductive organs testes ovaries in animals anther ovules in plants and gametangia in fungi of multicellular organisms NOTE there are sexually reproducing single celled organisms Meiosis Beginning to Ending Diploid Triploid Tetraploid Haploid Diploid Haploid Diploid Ploidy number of chromosomes is halved What would happen without meiosis Diploid Triploid Tetraploid Tetraploid Hexaploid Octaploid Meiosis Process Prophase I Metaphase I Anaphase I Telophase I Telophase II Anaphase II Metaphase II Prophase II Prophase I Chromosomes are replicated and condensed Homologous pairs present Centromere Homologous pair Sister chromatids n 2 ploidy 2 2n 4 Metaphase I Homologs line up side by side in the middle Tetrad two homologous chromosomes each consisting of two sister chromatids are paired together Creates four chromatids that can undergo crossing over n 2 ploidy 2 2n 4 Tetrad Homologous pair Centromere Sister chromatids Tetra d Or Metaphase I Doesn t matter which one is on which side Law of independent assortment Homologous pair Sister chromatids n 2 ploidy 2 2n 4 Law of independent assortment Independent Assortment Independent Assortment 2 possibilities for each pair for 2 pairs 22 4 possible combination s 08 Each of your parents could create 8 million different gametes 223 8 388 6 not including crossing over Metaphase of Mitosis Metaphase 1 of Meiosis Homologous pair f f F F l H o m o o g o u s p a i r Tetra d Anaphase I Homologs separate and move towards the poles of the cell Law of segregation Sister chromatids N 2 Ploidy 2 Law of segregation OR Anaphase I Homologs separate and move towards the poles of the cell Law of segregation Sister chromatids N 2 Ploidy 2 Law of segregation Telophase I Homologs are separating and two new cells are forming Ploidy is halved at the end of Telophase 1 Sister chromatids N 2 Ploidy 1 haploid N 2 Ploidy 1 haploid OR Telophase I Homologs are separating and two new cells are forming Ploidy is halved Sister chromatids N 2 Ploidy 1 haploid N 2 Ploidy 1 haploid Do you see where we re going with this Prophase II Chromosomes are still replicated sister chromatids are present No homologous pairs Sister chromatids N 2 Ploidy 1 haploid N 2 Ploidy 1 haploid Metaphase II Sisters align in the cell plate Sister chromatids N 2 Ploidy 1 haploid Metaphase 2 of Meiosis Sister chromatids Metaphase of Mitosis f f F F l H o m o o g o u s p a i r Anaphase II Sisters separate from one another and move towards the poles N 2 Ploidy 1 haploid Telophase II Sisters are separating new cells form N 2 Ploidy halploid Final 4 gametes All Haploid Table 1 Activity and location of chromosomes with regards to individual stages of meiosis Chromosome Activity State Meiosis Stage Meiosis I Meiosis II Chromosomes are replicated sisters present and connected via centromeres homologs present Prophase I Metaphase I Homologs lined up along the cell plate Anaphase I Telophase I Prophase II Metaphase II Sisters align along the cell plate in both cells Anaphase II Telophase II New cells form Homologs separate from one another and move towards the poles New cells forming ploidy has been halved Chromosomes replicated sisters present in both cells Sisters separate from one another and move towards the poles The separation of the alleles from one another is referred to as the law of segregation Table 2 Comparison of mitosis and meiosis processes Criteria Beginning Ploidy Ending Ploidy Cells Produced Purpose Mitosis 2n 2n 2 Meiosis 2n n 4 Production of genetically identical cells for repair and growth Production of gametes ICA Let s Practice Drawing Meiosis Q1 Draw a nucleus with 2 pairs of chromosomes in G1 The diploid individual is heterozygous for the B gene Bb on the first pair of chromosomes and heterozygous for the R Rr gene on the second pair of chromosomes Q2 This cell is in the seminiferous tubules of the testes in a human and is undergoing meiosis Model the chromosomes in metaphase of Meiosis I tetrad formation in both alignments For both Q1 and Q2 label all alleles and an example of a homologous pair and sister chromatids if present Q1 Draw a nucleus with 2 pairs of chromosomes in G1 The diploid individual is heterozygous for the B gene Bb on the first pair of chromosomes and heterozygous for the R Rr gene on the second pair of chromosomes ICA Let s Practice Drawing Meiosis Q1 Draw a nucleus with 2 pairs of chromosomes in G1 The diploid individual is heterozygous for the B gene Bb on the first pair of chromosomes and heterozygous for the R Rr gene on the second pair of chromosomes Q2 This cell is in the seminiferous tubules of the testes in a human and is undergoing meiosis Model the chromosomes in metaphase of Meiosis I tetrad formation in both alignments For both Q1 and Q2 label