PRODUCTION OF GAMETES MEIOSIS 1

eo/phases-of- meiosis?playlist=Biology KHAN ACADEMY LINK TO MEIOSIS

Click on link to watch Mr. Anderson talk about meiosis bc bc

ASEXUAL REPRODUCTION Bacteria and Amoeba reproduce using ___________________________ BINARY FISSION BACTERIA Amoeba

ASEXUAL REPRODUCTION HYDRA PLANARIA BUDDING & REGENERATION are used by organisms to reproduce asexually by MITOSIS

BINARY FISSION & MITOSIS Produces cells that are __________copies of parent cell IDENTICAL Human Somatic (body) cell Diploid (2n) 2n=46

MITOSIS Makes ___ cells genetically _________ to parent cell & to each other Makes ___ cells Makes _______________ Used by organisms to: increase size of organism, repair injuries, replace worn out cells 2 IDENTICAL 2n SOMATIC (body)

ADVANTAGES OF ASEXUAL REPRODUCTION Can make offspring at a faster rate: some bacteria can reproduce every 20 minutes Don’t need a partner

DISVANTAGES OF ASEXUAL REPRODUCTION ALL ALIKE Species CAN’T change and adapt One disease can wipe out whole population

SEXUAL REPRODUCTION Combines genetic material from 2 parents (sperm & egg) so offspring are genetically __________ from parents DIFFERENT

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

MEIOSIS is the way… to make cells with ½ the number of chromosomes for sexual reproduction

CHARACTERISTICS OF LIVING THINGS ALL LIVING THINGS ______________ REPRODUCE

15 MEIOSIS Occurs only in ______________ (testes or ovaries) Male: _____________________ Female: ___________________ GONADS SPERMATOGENESIS OOGENESIS

MAKING SPERM & EGGS

___________________= MAKING MATURE SPERM Mature & grow flagella SPERMATOGENESIS

Replication (interphase) Meiosis I Meiosis II SPERM SPERMATOGENESIS

POLAR BODIES Produces: 1 “good” egg 3 CYTOPLASM DIVIDES UNEVENLY __________________ = MAKING a MATURE EGG OOGENESIS

Life History of OVUM(EGG) as a fetus, oogonia divide to produce millions by mitosis but most degenerate Some develop into primary oocytes & stop in prophase stage of meiosis I – 200,000 to 2 million present at birth – 40,000 remain at puberty but only 400 mature during a woman’s life Each month, hormones cause meiosis I to resume in several follicles so that metaphase II is reached by ovulation Penetration by the sperm causes the final stages of meiosis to occur

Sperm donates DNA WHY MAKE ONLY ONE “GOOD” EGG? Most of the cell parts and nutrients needed for baby come from EGG!

“Self digest” Using ______________ POLAR BODIES DEGENERATE (DIE) LYSOSOMES = __________________ “cell suicide” for good of organism APOPTOSIS

OVUM (EGG) Replication (interphase Meiosis I Meiosis II   

24 FERTILIZATION spermegg ZYGOTE The fusion of a sperm and egg to form a ZYGOTE. A ZYGOTE is a fertilized egg n=23 egg sperm n=23 2n=46 zygote

Sperm provides DNA All the starting nutrients, organelles, molecule building blocks, etc. have to come from the egg. OVUM SPERM

COMPARISON OF OOGENESIS & SPERMATOGENESIS

DIPLOID & HAPLOID Most cells have 2 copies of each chromosome = _____ or_________ (one from mom; one from dad) All BODY (___________) cells are diploid DIPLOID2n HOMOLOGOUS CHROMOSOMES SOMATIC

eplication%20of%20a%20Chromos ome.htm WATCH AN ANIMATION OF HOW A CHROMOSOME IS REPLICATED

DIPLOID & HAPLOID Sex cells or Gametes have only one copy of each chromosome = _____or __________ All sperm and egg cells are haploid HAPLOID1n

MEIOSIS Makes ____ cells genetically different from parent cell & from each other Makes _____ cells Makes ______________ Used for ____________ 4 1n GAMETES (sperm & eggs) sexual reproduction

MEIOSIS

32 INTERPHASE I mitosis Similar to mitosis interphase CHROMOSOMES(S phase) CHROMOSOMES REPLICATE (S phase) chromosome CHROMATIDS centromeres Each duplicated chromosome consist of TWO IDENTICAL SISTER CHROMATIDS attached at their centromeres CENTRIOLE CENTRIOLE PAIRS also replicate.

33 Interphase I NUCLEUSNUCLEOLUS NUCLEUS AND NUCLEOLUS visible. Nuclear membrane Nucleolus Cell membrane Chromatin

34 MEIOSIS I

35 Stages of Meiosis I Cell division chromosomeone- half Cell division that reduces the chromosome number by one- half Four phases Four phases: a.Prophase I b.Metaphase I c.Anaphase I d.Telophase I

36 Prophase I Longest and most complex phase (90%) Longest and most complex phase (90%) Chromosomes Chromosomes condense Synapsishomologous chromosomes tetrad Synapsis occurs: homologous chromosomes come together to form a tetrad Tetradchromosomes chromatids Tetrad is two chromosomes or four chromatids (sister and nonsister chromatids)

37 Prophase I - Synapsis Homologous chromosomes Sister chromatids Tetrad

39 Homologous Chromosomes chromosomesmaternal paternal Pair of chromosomes (maternal and paternal) that are similar in shape and size (tetrads) Homologous pairs (tetrads) carry genes controlling the same inherited traits locus(position of a gene) Each locus (position of a gene) is in the same position on homologues

40 Homologous Chromosomes PaternalMaternal eye color locus eye color locus hair color locus hair color locus

41 Crossing Over Crossing over (variation) chromatids chiasmata Crossing over (variation) may occur between nonsister chromatids at the chiasmata Crossing over chromatids chromatid Crossing over: segments of nonsister chromatids break and reattach to the other chromatid Chiasmata (chiasma) crossing over Chiasmata (chiasma) are the sites of crossing over

42 Prophase I Centrioles Spindle fiber Aster fibers

43 Metaphase I Shortest phase Shortest phase Tetradsmetaphase plate Tetrads align on the metaphase plate Independent assortment occurs Independent assortment occurs Chromosomes separate randomly to the poles of the cells Chromosomes separate randomly to the poles of the cells

44 Metaphase I Independent assortment causes variation in the forming cells Orientation of homologous pair to poles is random Formula for determining variation: Formula: 2 n Example: 2n = 4 then n = 2 then n = 2 thus 2 2 = 4 combinations thus 2 2 = 4 combinations

45 Metaphase I Metaphase plate OR Metaphase plate

46 Question: In terms of Independent Assortment, how many different combinations of sperm could a human male produce? In terms of Independent Assortment, how many different combinations of sperm could a human male produce?

47 Answer Formula: 2 n Formula: 2 n Human chromosomes: Human chromosomes: 2n = 46 2n = 46 n = 23 n = = ~8 million combinations 2 23 = ~8 million combinations

48 Anaphase I Homologous chromosomes Homologous chromosomes separate and move towards the poles Sister chromatids centromeres Sister chromatids remain attached at their centromeres

49 Anaphase I

50 Telophase I haploid chromosomes Each pole now has haploid set of chromosomes 1n = 23 (human) 1n = 23 (human) Cytokinesis Cytokinesis occurs and two haploid daughter cells are formed

51 Telophase I

52

53 MEIOSIS II

54 Meiosis II Short or No interphase II Short or No interphase II DNA NOT replicated again DNA NOT replicated again Remember: Meiosis II mitosis Remember: Meiosis II is similar to mitosis Prophase I, Metaphase II, Anaphase II, and Telophase II Prophase I, Metaphase II, Anaphase II, and Telophase II

55 Prophase II prophasemitosis Same as prophase in mitosis Nuclear envelope breaks down and the spindle apparatus forms Nuclear envelope breaks down and the spindle apparatus forms

56 Metaphase II metaphasemitosis Same as metaphase in mitosis Chromatids lined up at equator Chromatids lined up at equator Metaphase plate

57 Anaphase II anaphasemitosis Same as anaphase in mitosis Sister chromatids separate Sister chromatids separate

58 Telophase II telophasemitosis Same as telophase in mitosis Nuclei reform Cytokinesis Cytokinesis occurs Remember: Four haploid daughter cells produced Remember: Four haploid daughter cells produced Gametes = sperm or egg Gametes = sperm or egg

59 Telophase II

60

61 Genetic Variation

62 Variation Important to the survival of populations Important to the survival of populations Aids in natural selection Aids in natural selection Strongest individuals are able to survive and reproduce Strongest individuals are able to survive and reproduce

63 Question What are the three sources of genetic variation in sexual reproduction? What are the three sources of genetic variation in sexual reproduction?

64 Answer: 1.Crossing Over (Prophase I) (Prophase I) 2. Independent Assortment (Metaphase I) 3. Random Fertilization (sperm joins with egg)

65 Remember: Variation is helpful to the survival of a species!

66 Question: 20 chromosomes(2n = 20) chromosomes A diploid cell containing 20 chromosomes (2n = 20) at the beginning of meiosis would, at its completion, produce cells containing how many chromosomes?

67 Answer: 10 chromosomes (haploid) 10 chromosomes (haploid) 1n = 10 1n = 10

68 Question: 40 CHROMOSOMES chromosomes in each cell A cell containing 40 CHROMOSOMES at the beginning of meiosis would, at its completion, produce how many cells and how many chromosomes in each cell?

69 ANSWER: FOUR CELLS with 20 chromosomes each FOUR CELLS with 20 chromosomes each

Chromosome Numbers of Some Common Organisms ORGANISM BODY CELL (2n) DIPLOID GAMETES (n) HAPLOID HUMAN4623 GARDEN PEA147 FRUIT FLY84 TOMATO2412 DOG7839 CHIMPANZEE4824 LEOPARD FROG2613 CORN2010 MICROSCOPIC ROUNDWORM126 CHICKEN7839 ANT21 HOUSE MOUSE4020 CRAYFISH RABBIT4422 DEER6834 ADDERS-TONGUE FERN (PLANT) HORSE6432 EARTHWORM3618 DOVE7839 DOLPHIN4422

MEIOSIS I Section 11-4 Figure Meiosis

Section 11-4 Figure Meiosis MEIOSIS I

Meiosis I Section 11-4 Figure Meiosis MEIOSIS I

Section 11-4 Figure Meiosis MEIOSIS I

Section 11-4 Figure Meiosis MEIOSIS I

Meiosis I results in two haploid (N) daughter cells, each with half the number of chromosomes as the original. Prophase IIMetaphase IIAnaphase IITelophase 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. Figure Meiosis II Section 11-4 Meiosis II

Meiosis I results in two haploid (N) daughter cells, each with half the number of chromosomes as the original. Prophase IIMetaphase IIAnaphase IITelophase 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. Section 11-4 Figure Meiosis II

Meiosis I results in two haploid (N) daughter cells, each with half the number of chromosomes as the original. Prophase IIMetaphase IIAnaphase IITelophase 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. Section 11-4 Figure Meiosis II Meiosis II

Meiosis I results in two haploid (N) daughter cells, each with half the number of chromosomes as the original. Prophase IIMetaphase IIAnaphase IITelophase 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. Section 11-4 Figure Meiosis II Meiosis II

Meiosis I results in two haploid (N) daughter cells, each with half the number of chromosomes as the original. Prophase IIMetaphase IIAnaphase IITelophase 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. Section 11-4 Figure Meiosis II Meiosis II

81 REVIEW

WHAT MAKES MEIOSIS DIFFERENT FROM MITOSIS? 1.SYNAPSIS & CROSSING OVER (PROPHASE I) 2.SEGREGATION & INDEPENDENT ASSORTMENT (ANAPHASE I) 3. Skip INTERPHASE II (NO S) CELL DIVIDES TWICE, BUT… ONLY COPIES DNA ONCE

WHAT MAKES MEIOSIS DIFFERENT ? 1.Homologous chromosomes pair up during ________________ = ______________ SYNAPSIS This group of FOUR (4) chromatids is called a _________________ TETRAD PROPHASE I

WHAT MAKES MEIOSIS DIFFERENT? 1. Exchange of DNA between homologous pairs = _____________ during PROPHASE I CROSSING OVER Allows shuffling of genetic material= ________________ GENETIC VARIAION

Meiotic%20Recombination%20Bet ween%20Linked%20Genes.htm CLICK ON LINK BELOW TO WATCH A CROSSING OVER ANIMATION

HOMOLOGOUS CHROMOSOMES SAME SIZE SAME SHAPE CARRY GENES for the SAME TRAITS BUT ______________! NOT IDENTICAL

CROSSING OVER Allows for_________________ in different combinations After crossing over, chromatid arms are________________ anymore Image modified by Riedell rearranging of DNA NOT IDENTICAL

WHAT MAKES MEIOSIS DIFFERENT ? 2. Separation during ANAPHASE I INDEPENDENT ASSORTMENT Separates gene choices and allows shuffling of genetic material or genetic diversity SEGREGATION &

SEGREGATION (Anaphase I)

SEGREGATION & CROSSING OVER together make even more combinations

INDEPENDENT ASSORTMENT

INDEPENDENT ASSORTMENT at ANAPHASE I Lots of different combinations are possible! This is why you don’t look exactly like your brothers and sisters even though you share the same parents!

WHAT MAKES MEIOSIS DIFFERENT ? Crossing over Segregation Independent assortment are ALL ways MEIOSIS results in =______________________________ So daughter cells are ______________ from parents and from each other DIFFERENT GENETIC RECOMBINATION

WHAT MAKES MEIOSIS DIFFERENT ? 3. Skip INTERPHASE II (No S) CELL DIVIDES TWICE, BUT … ONLY COPIES ITS DNA ONCE G1G1 G2G2 S   PM  A T C G1G1    MITOSIS: MEIOSIS:    SG2G2 PM ATC PM A TC ( I ) ( II )

98 REVIEW: COMPARING MITOSIS AND MEIOSIS

MITOSISMITOSIS vs MEIOSIS INTERPHASE INTERPHASE IMEIOSIS DNA is spread out as chromatin Nuclear membrane/ nucleolus visible DNA is copied during S phase Makes everything new cell needs in G 2 SAME AS MITOSIS

MITOSIS vs MEIOSIS PROPHASE PROPHASE I DNA shortens and thickens into chromosomes Nuclear membrane/ nucleolus disassemble Centrioles/ spindle fibers appear SAME AS MITOSIS EXCEPT: Homologous pairs match up

MITOSIS vs MEIOSIS METAPHASE METAPHASE I Chromosomes line up in middle (no homologs) with homologous partner SAME AS MITOSIS EXCEPT:

MITOSIS vs MEIOSIS ANAPHASE ANAPHASE I Chromatids split APART Chromatids stay together Homologous pairs split

MITOSIS vs MEIOSIS TELOPHASE TELOPHASE I See TWO nuclei Nuclear membrane/ nucleolus reassemble DNA spreads out as chromatin Spindle/centrioles disassemble SAME AS MITOSIS

MITOSIS vs MEIOSIS CYTOKINESIS CYTOKINESIS I Cytoplasm splits into 2 cells SAME AS MITOSIS

MITOSIS vs MEIOSIS INTERPHASE II DNA is spread out as chromatin Nuclear membrane/ nucleolus visible DNA is copied during S phase SKIP INTERPHASE II DNA NOT COPIED

MITOSIS vs MEIOSIS PROPHASE PROPHASE II DNA scrunches into chromosomes Nuclear membrane/ nucleolus disassemble Centrioles/ spindle fibers appear SAME AS MITOSIS

MITOSIS vs MEIOSIS METAPHASE METAPHASE II Chromosomes line up in middle SAME AS MITOSIS

MITOSIS vs MEIOSIS ANAPHASE ANAPHASE II Chromatids split and move apart SAME AS MITOSIS

MITOSIS vs MEIOSIS TELOPHASE TELOPHASE II Two nuclei Nuclear membrane/ nucleolus reassemble Centrioles/spindle fibers disassemble DNA spreads out as chromatin SAME AS MITOSIS

MITOSIS vs MEIOSIS CYTOKINESIS CYTOKINESIS II Cytoplasm splits SAME AS MITOSIS

Ways Meiosis is different? Homologous pairs match up & trade DNA (SYNAPSIS & CROSSING OVER) in PROPHASE I SEGREGATION & INDEPENDENT ASSORTMENT in Anaphase I create genetic recombination Skipping INTERPHASE II- (Dividing TWICE but copying DNA once) produces 1n HAPLOID cells

CLICK TO WATCH ANIMATIONS OF MEIOSIS hill.com/olcweb/cgi/pluginpop.cgi? it=swf::535::535::/sites/dl/free/ /120074/bio19.swf::Stages %20of%20Meiosis nt/animations/content/meiosis.html

Centrosomes (with centriole pairs) Sister chromatids Chiasmata spindle Tetrad Nuclear envelope Chromatin Centromere (with kinetochore) Microtubule attached to kinetochore Tetads line up Metaphase plate Homologous chromosomes separate Sister chromatids remain attached Pairs of homologous chromosomes split up Chromosomes duplicate Homologous chromosomes (red and blue) pair and exchange segments; 2n = 6 in this example INTERPHASE MEIOSIS I: Separates homologous chromosomes PROPHASE I METAPHASE I ANAPHASE I Interphase and meiosis I

TELOPHASE I AND CYTOKINESIS PROPHASE II METAPHASE II ANAPHASE II TELOPHASE II AND CYTOKINESIS MEIOSIS II: Separates sister chromatids Cleavage furrow Sister chromatids separate Haploid daughter cells forming During another round of cell division, the sister chromatids finally separate; four haploid daughter cells result, containing single chromosomes Two haploid cells form; chromosomes are still double Telophase I, cytokinesis, and meiosis II 1 2 3

CLICK ON THE LINK TO WATCH AN ANIMATION OF THE COMPARISON OF MEIOSIS AND MITOSIS hill.com/olcweb/cgi/pluginpop.cgi? it=swf::535::535::/sites/dl/free/ /120074/bio17.swf::Comp arison%20of%20Meiosis%20and% 20Mitosis

When does it occur? One or Two? Occurs or not? If yes when? Occurs or not? If yes when? One or two? Diploid or Haploid? One or two? Diploid or Haploid? What is purpose of Mitosis?

diploid haploid