Meiosis and Genetics: Cell Division & Genetic Shuffling PDF

Meiosis  Genetics Terminology SEXUALLY reproducing eukaryotes, have 2 types of cells… 1. somatic cells 2. sex cells (a.k.a. gametes) Image: Superficial human anatomy, Mikael Häggström& Rainer Zenz; Sperm & egg, Wikipedia From the Virtual Cell Biolo...

Meiosis  Genetics Terminology SEXUALLY reproducing eukaryotes, have 2 types of cells… 1. somatic cells 2. sex cells (a.k.a. gametes) Image: Superficial human anatomy, Mikael Häggström& Rainer Zenz; Sperm & egg, Wikipedia From the Virtual Cell Biology Classroom on ScienceProfOnline.com  What is cell division of gametes called? Meiosis - A single germ cell divides into four unique daughter cells. - Daughter cells have half the # of chromosomes as parent cell, so they considered haploid. Image: Overview of Meiosis, National Institutes of Health From the Virtual Cell Biology Classroom on ScienceProfOnline.com Genetics Terminology: Ploidy Refers to the number of sets of chromosomes in cells. Haploid – one copy of each chromosome – designated as “n”, the number of chromosomes in one “set” - gametes From the Virtual Cell Biology Classroom on ScienceProfOnline.com Genetics Terminology: Ploidy Diploid – two sets of chromosomes - two of each chromosome – designated as “2n” - somatic cells Diploid organisms receive one of each type of chromosome from female parent (maternal chromosomes) and one of each type of chromosome from male parent (paternal chromosomes) From the Virtual Cell Biology Classroom on ScienceProfOnline.com  Genetics Terminology: Homologues Chromosomes exist in homologous pairs in diploid (2n) cells. Exception: Sex chromosomes (X, Y). Other chromosomes, known as autosomes, they have homologues. From the Virtual Cell Biology Classroom on ScienceProfOnline.com  Karyotype Q: Which, of the top two karyotypes is replicated? Q: How many homologous pair in each karyotype? Q: How is the bottom karyotype different from the top two? From the Virtual Cell Biology Classroom on ScienceProfOnline.com Image: Karyotype, National Human Genome Research Institute  Asexual Reproduction – Many single-celled organisms reproduce by splitting, budding. – Some multicellular organisms can reproduce asexually, produce clones (offspring genetically identical to parent). – Q: What type of cell division is asexual reproduction? Image: Paatrick Star, Nickelodeon; From the Virtual Cell Biology Classroom on ScienceProfOnline.com Hydra budding, Lifetrance;  Sexual Reproduction Fusion of two gametes to produce a single zygote. Introduces greater genetic variation, allows genetic recombination. With exception of self- fertilizing organisms, zygote has gametes from two different parents. Images: Peter, Lois & Stewie, The Family Guy From the Virtual Cell Biology Classroom on ScienceProfOnline.com  Meiosis - Sex Cell (Gamete) Formation In meiosis, there are 2 divisions of the nucleus: meiosis I & meiosis II Image: Overview of Meiosis, National Institutes of Health From the Virtual Cell Biology Classroom on ScienceProfOnline.com Meiosis I Meiosis II From the Virtual Cell Biology Classroom on ScienceProfOnline.com Image: Meiosis diagram, Marek Kultys  Meiosis & Sexual Reproduction Life Cycle Mitosis * * * From the Virtual Cell Biology Classroom on ScienceProfOnline.com Image: Animal Life Cycle, Dr. T’s Bio 328 Genetics  Genetic Variation in Diploid Organisms Fusion of sperm and egg results in unique offspring. From the Virtual Cell Biology Classroom on ScienceProfOnline.com Image: Meiosis diagram, Marek Kultys  Genetic Variation in Diploid Organisms But not only because the young are a product of two individuals with different genetic makeup. From the Virtual Cell Biology Classroom on ScienceProfOnline.com Image: Meiosis diagram, Marek Kultys  Genetic Variation in Diploid Organisms Meiosis “shuffles” the genes so that the an individual’s gametes are genetically different from one another. How is this shuffling accomplished? From the Virtual Cell Biology Classroom on ScienceProfOnline.com Image: Meiosis diagram, Marek Kultys  Genetic shuffling of Meiosis I In addition to a new combination of chromosomes resulting from fertilization, there are also events in Meiosis I that shuffle the genes. 1. Crossing over in Prophase I. 2. Independent assortment in Metaphase I. From the Virtual Cell Biology Classroom on ScienceProfOnline.com  Crossing Over Homologues break at identical locations, then rejoin opposite partners. This creates new combinations of the alleles on each chromosome. Image: Meiosis diagram, Marek Kultys ; Crossing over, Thomas From the Virtual Cell Biology Classroom on ScienceProfOnline.com Hunt Morgan, Molecular crossing over, David Hall  Crossing Over Occurs randomly several times on every chromosome. Results in mixing of the genes you inherited from your parents. Image: Meiosis diagram, Marek Kultys ; Crossing over, Thomas From the Virtual Cell Biology Classroom on ScienceProfOnline.com Hunt Morgan, Molecular crossing over, David Hall Independent Assortment  Males produce sperm throughout life, after Spermatogenesis the onset of puberty, about 1,500 sperm per second. From the Virtual Cell Biology Classroom on ScienceProfOnline.com Image: Spermatogenesis, Wiki  Oogenesis Oogenesis in females is probably complete either before or shortly after birth. During oogenesis, three polar bodies develop as the mature ovum is generated. Polar bodies contain little cytoplasm and eventually degenerate. From the Virtual Cell Biology Classroom on ScienceProfOnline.com Image: Oogenesis, Wiki  Mitosis vs. Meiosis 1n 2n Daughter cells different from Clone parent cell and from each other. Same genetic Daughter cells have ½ the information in number of chromosomes as parent cell and somatic cell. daughter cell. Shuffling the genes Give me another (Mix it up!) one just like the other one! From the Virtual Cell Biology Classroom on ScienceProfOnline.com Image: Mitosis diagram & Meiosis diagram, Marek Kultys From the Virtual Cell Biology Classroom on ScienceProfOnline.com