MEIOSIS Genetics Slide show modified from Kelly Riedell

MEIOSIS Genetics Slide show modified from Kelly Riedell, Tracy Jackson and Kim Foglia

BINARY FISSION & MITOSIS Produces cells that are genetically identical _____ copies of parent cell

Asexual vs. Sexual Reproduction n In asexual reproduction q. One parent produces genetically identical offspring by mitosis n. Ex: budding, binary fission, spores, etc. Parent Bud 0. 5 mm

ADVANTAGES OF ASEXUAL REPRODUCTION • Can make offspring faster • Don’t need a partner; only 1 “parent” needed

DISVANTAGES OF ASEXUAL REPRODUCTION • ALL ALIKE (“clones”) • Species usually CAN’T change and adapt • One disease can wipe out whole population

SEXUAL REPRODUCTION • Combines genetic material from 2 parents (sperm & egg) • Offspring are genetically different and unique from parents

ADVANTAGES OF SEXUAL REPRODUCTION • Allows for variation in population • Individuals can be different • Provides foundation for EVOLUTION • Allow species adapt to changes in their environment

EGG + SPERM If egg and sperm had same number of chromosomes as other body cells (2 n). . . baby would have too many chromosomes!

MEIOSIS is the way… to make cells with ½ the number of chromosomes for sexual reproduction http: //waynesword. palomar. edu/lmexer 2 a. htm

DIPLOID Most cells have 2 copies of each chromosome DIPLOID 2 n = _______ (one from mom; one from dad) HOMOLOGOUS CHROMOSOMES SOMATIC ) cells are diploid All BODY (____

Chromosomes that determine the sex of an organism = Sex chromosomes _________ All other chromosomes that do NOT determine autosomes gender = _____ Humans have two sex chromosomes (1 pair), which are NOT homologous 44 autosomes and _____ XX or XY

HAPLOID Some cells have only one copy of each HAPLOID 1 n chromosome = _______ All sperm and egg cells are haploid

Review…MITOSIS • Makes ___ 2 cells genetically identical _____ to parent cell & to each other 2 n • Makes ___ cells • Makes _____ SOMATIC (body) • Used by organisms to: increase size of organism, repair injuries, replace worn out cells http: //waynesword. palomar. edu/lmexer 2 a. htm

MEIOSIS 4 cells • Makes ____ genetically different from parent cell & from each other 1 n cells • Makes __________ Gametes (sperm & eggs) Sexual reproduction • Used for ______ http: //waynesword. palomar. edu/lmexer 2 a. htm

2 karyokinesis events occur in meiosis!

WHAT MAKES MEIOSIS DIFFERENT FROM MITOSIS ? 1. 2 divisions instead of 1 – Meiosis I and Meiosis II (PMATc I & PMATc II) 2. SYNAPSIS & CROSSING OVER (PROPHASE I) 1. INDEPENDENT ASSORTMENT and SEGREGATION (ANAPHASE I) 1. 4 cells are made and they are haploid 2. Daughter cells are genetically DIFFERENT

WHAT MAKES MEIOSIS DIFFERENT FROM MITOSIS? 1. Homologous chromosomes pair up during ________ PROPHASE I = called SYNAPSIS (Pairing of two homologous chromosomes) This group of FOUR (4) chromatids is called a TETRAD _________ Images modified from: http: //www. emc. maricopa. edu/faculty/farabee/BIOBK/Crossover. gif

WHAT MAKES MEIOSIS DIFFERENT FROM MITOSIS? 1. Exchange of DNA between OVER homologous pairs = CROSSING _______ during PROPHASE I Allows shuffling of genetic material called genetic recombination Place(s) where crossing over happens CHIASMATA = __________ http: //highered. mcgraw-hill. com/sites/0072437316/student_view 0/chapter 12/animations. html#

CROSSING OVER rearranging of DNA • Allows for_________ in different combinations • After crossing over, chromatid arms NOT IDENTICAL anymore are________ http: //sps. k 12. ar. us/massengale/genetics%20 tutorial. htm

INDEPENDENT ASSORTMENT the random alignment of homolgous chromosome pairs at metaphase plate (Metaphase I) http: //highered. mheducation. com/olcweb/cgi/pluginpop. cgi? it=swf: : 535: : /sites/dl/free/0072437316/120074/bio 18. swf: : Random%20 Orientatio n%20 of%20 Chromosomes%20 During%20 Meiosis

Random Orientation of Chromosomes During Meiosis http: //highered. mheducation. com/olcweb/cgi/plugi npop. cgi? it=swf: : 535: : /sites/dl/free/00724373 16/120074/bio 18. swf: : Random%20 Orientation%2 0 of%20 Chromosomes%20 During%20 Meiosi

SEGREGATION separating of homologous pairs (Anaphase I)

SEGREGATION & CROSSING OVER together make even more gamete combinations http: //waynesword. palomar. edu/lmexer 2 a. htm

INDEPENDENT ASSORTMENT and SEGREGATION at METAPHASE/ANAPHASE I Lots of different combinations are possible! 3 rd animation http: //highered. mcgrawhill. com/sites/0072437316/student_view 0/chapter 12/animati This is why you don’t look exactly like your brothers and sisters even though you share the same parents!

GENETIC RECOMBINATION comes from: • Crossing over • Segregation • Independent assortment • Random fertilization

PHASES OF MEIOSIS Figure 11 -15 Meiosis Section 11 -4 Meiosis I = MAJOR differences from mitosis

Meiosis II: Figure 11 -17 Meiosis II NOTEno Interphase II- instead short intermission Section 11 -4 (no growth or DNA replication occurs) Prophase II Meiosis I results in two haploid (N) daughter cells, each with half the number of chromosomes as the original. Metaphase II Anaphase II Telophase II The chromosomes line up in a similar way to the metaphase stage of mitosis. The sister chromatids separate and move toward opposite ends of the cell. Meiosis II results in four haploid (N) daughter cells.

Stages of Meiosis • http: //highered. mheducation. com/olcweb/cg i/pluginpop. cgi? it=swf: : 535: : /sites/dl/fr ee/0072437316/120074/bio 19. swf: : Stages% 20 of%20 Meiosis

MITOSIS vs. MEIOSIS INTERPHASE http: //www. pbs. org/wgbh/nova/baby/divi_flash. html 2 n cell • • • INTERPHASE I 2 n cell DNA is spread out as chromatin Nuclear membrane/nucleolus visible DNA is copied during S phase Makes stuff new cell needs in G 2 Cell Grows SAME AS MITOSIS

MITOSIS vs. MEIOSIS PROPHASE I 2 n cell • • • DNA packs into chromosomes DNA packs into • Nuclear membrane/ nucleolus chromosomes disappear Nuclear membrane/ nucleolus • Spindle fibers appear and attach to disappear chromosomes Spindle fibers appear and • Centrosomes migrate to poles attach to chromosomes SYNAPSIS and CROSSING Centrosomes migrate to poles OVER OCCURS

MITOSIS vs. MEIOSIS METAPHASE 2 n cell METAPHASE I 2 n cell • Chromosomes line up in middle in single file in middle with homologous partner line • Independent assortment occurs

MITOSIS vs. MEIOSIS ANAPHASE I 2 n cell • Polar fibers lengthen cell • Chromatids split 2 n cell • Polar fibers lengthen cell • Chromatids stay together Homologous pairs split (SEGREATION OCCURS)

MITOSIS vs. MEIOSIS TELOPHASE I 2 n cell • • See TWO nuclei Nuclear membrane/ nucleolus return DNA spreads out as chromatin Spindle fibers disappear n cell SAME AS MITOSIS

MITOSIS vs. MEIOSIS CYTOKINESIS 2 n cell CYTOKINESIS I n cell DIPLOID Cytoplasm splits into 2 cells using HAPLOID SAME AS MITOSIS

MITOSIS vs. MEIOSIS INTERPHASE II 2 n cell • • • DNA is spread out as chromatin Nuclear membrane/nucleolus visible DNA is copied during S phase Makes stuff new cell needs in G 2 Cell Grows n cell SKIP INTERPHASE II DNA NOT COPIED

MITOSIS vs. MEIOSIS PROPHASE II n cell 2 n cell • • DNA packs into chromosomes Nuclear membrane/ nucleolus disappear Spindle fibers appear and attach to chromosomes Centrosomes migrate to poles SAME AS MITOSIS (but cell is now HAPLOID)

MITOSIS vs. MEIOSIS METAPHASE II n cell 2 n cell • Chromosomes line up in middle in a single file line SAME AS MITOSIS (but cell is now HAPLOID)

MITOSIS vs. MEIOSIS ANAPHASE II 2 n cell Chromatids split and move apart n cell SAME AS MITOSIS (but cell is now HAPLOID)

MITOSIS vs. MEIOSIS TELOPHASE II 2 n cell • See TWO nuclei • Nuclear membrane/ nucleolus return • DNA spreads out as chromatin SAME AS MITOSIS • Spindle fibers disappear (but cell is now HAPLOID)

MITOSIS vs. MEIOSIS CYTOKINESIS II RESULTS IN FOUR n cell RESULTS IN TWO 2 n cell Cytoplasm splits SAME AS MITOSIS (but cell is now HAPLOID) http: //www. pbs. org/wgbh/nova/baby/divi_flash. html

Ways Meiosis is different? Unique Features of Meiosis: http: //highered. mheducation. com/olcweb/cgi/pluginpop. cgi? it=swf: : 535: : /sites/dl/free/0072437316/120074 /bio 16. swf: : Unique%20 Features%20 of%20 Meiosis Mitosis vs. Meiosis: http: //highered. mheducation. com/olcweb/cgi/pluginpop. cgi? it=swf: : 535: : /sites/dl/free/0072437316/120074 /bio 17. swf: : Comparison%20 of%20 Meiosis%20 and%20 Mitosis

MAKING SPERM & EGGS

• Gametogenesis = – process of forming gametes (n) from diploid (2 n) cells 2 TYPES: • Spermatogenesis = process of forming sperm cells • After division all 4 cells undergo differentiation to become sperm cells • The cells elongate and grow tail (a flagella) • Oogenesis = process of forming ovum (egg) cell and 3 polar bodies

Starts with a 2 n cell called a GERM LINE CELL

SPERMATOGENESIS __________= MAKING MATURE SPERM Mature & grow flagella

Spermatogenesis • https: //www. youtube. com/watch? v=6 f. Ba 8 Uq Eano

• Sperm provides DNA to the zygote. • All the starting nutrients, organelles, molecule building blocks, etc. have to come from the ovum (egg)

OOGENESIS _________ = MAKING a MATURE EGG Produces: 1 “good” ovum (egg) 3 POLAR BODIES • CYTOPLASM DIVIDES UNEVENLY • Polar bodies are smaller and are later destroyed using APOPTOSIS

Oogenesis • https: //www. youtube. com/watch? v=kj. OOAa ze-Ng

Putting it all together… meiosis fertilization mitosis + development 46 23 egg 46 sperm 23 46 4646 46

What happens when meiosis goes wrong? NONDISJUNCTION!!!