Meiosis the cellular basis of sexual reproduction
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Meiosis: The Cellular Basis of Sexual Reproduction ( 감수분열 : 유성생식의 세포적 기반 ) PowerPoint PPT Presentation


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Meiosis: The Cellular Basis of Sexual Reproduction ( 감수분열 : 유성생식의 세포적 기반 ). Chapter 11. 염색체는 감수분열 첫 번째 분열의 중기에 정렬된다 . 감수분열은 난자와 정자 같은 배우체를 형성하는 시기이다 . 11.1 The Mechanisms of Meiosis. Meiosis is based on the interactions and distribution of homologous chromosome pairs

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Meiosis: The Cellular Basis of Sexual Reproduction ( 감수분열 : 유성생식의 세포적 기반 )

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Meiosis the cellular basis of sexual reproduction

Meiosis: The Cellular Basis of Sexual Reproduction(감수분열: 유성생식의 세포적 기반)

Chapter 11


Meiosis the cellular basis of sexual reproduction

염색체는 감수분열 첫 번째 분열의 중기에 정렬된다. 감수분열은 난자와 정자 같은 배우체를 형성하는 시기이다.


11 1 the mechanisms of meiosis

11.1 The Mechanisms of Meiosis

  • Meiosis is based on the interactions and distribution of homologous chromosome pairs

  • Meiosis produces four genetically different cells with half the parental chromosomes


Sexual reproduction

Sexual Reproduction

  • Sexual reproduction(유성생식) produces offspring by union of male and female gametes (배우자)(sperm and egg)

    • Meiosis produces gametes with half chromosome number

    • Evolutionary advantage: Genetic shuffling of sex


Fertilization

Fertilization

  • Fertilization fuses nuclei of egg and sperm

    • Zygote (접합자) cell produced by fertilization

    • Restores parental chromosome number


Homologous chromosome pairs

Homologous Chromosome Pairs

  • Paternal chromosomes(부계염색체)from male parent, maternal chromosomes (모계염색체) from female parent

    • Homologous chromosome pairs

    • Alleles may be different within homologous pairs

  • Meiosis separates homologous pairs

    • Before meiosis, diploid (2n)

    • After meiosis, haploid(n)


Meiosis the cellular basis of sexual reproduction

그림 11.1. 감수분열의 주기와 수정


Meiotic cell cycle

Meiotic Cell Cycle

  • Mitosis (유사분열; 체세포분열) and meiosis (감수분열) compared

    • Both: Similar cell divisions, meiosis divides twice

    • Mitosis: Two identical daughter cells, diploid (이배체)

    • Meiosis: Four genetically different cells, haploid (반수체)

  • Premeiotic interphases (감수분열 전 간기) similar to mitotic interphase

    • Chromosomes copied into sister chromatids (자매염색분체)


Meiosis i

Meiosis I

  • Meiosis I: First meiotic division

    • Recombination exchanges segments between homologues

    • Produces two haploid cells with chromatids attached


Meiosis ii

Meiosis II

  • Meiosis II: Second meiotic division

    • Sister chromatids separate into separate cells

    • Produces 4 recombined haploid cells


Meiosis the cellular basis of sexual reproduction

그림 11.2. 두번의 감수분열에 의한 4개의 반수체 핵의 생산


Meiotic cell cycle 1

Meiotic Cell Cycle (1)

  • Prophase I (전기 I)

    • Sister chromatids condense to chromosomes

    • Synapsis (접합) (pairing of homologs)

    • Tetrads (사분체) (Fully paired homologs)

    • Recombination(재조합)mixes alleles across tetrads

  • Prometaphase I (전중기 I)

    • Nuclear envelope (핵막) breaks down

    • Kinetochores (동원체에 있는 방추사부착점) attach to polar spindles (극 방추사)


Meiosis the cellular basis of sexual reproduction

그림 11.3 -1. 감수분열


Meiotic cell cycle 2

Meiotic Cell Cycle (2)

  • Metaphase I and Anaphase

    • Tetrads align on metaphase plate

    • Homologs segregate, move to poles (sister chromatids attached)

    • Nondisjunction(비분리) creates abnormal chromosome numbers

  • Telophase I and Interkinesis(분열간기)

    • No change in chromosomes

    • Spindle disassembles


Meiosis the cellular basis of sexual reproduction

그림 11.3 -2


Meiotic cell cycle 3

Meiotic Cell Cycle (3)

  • Prophase II, Prometaphase II, and Metaphase II

    • Chromosomes condense, spindles form

    • Nuclear envelope breaks, kinetochores form

    • Chromosomes align on metaphase plate(중기판)

  • Anaphase II and Telophase II

    • Spindles separate chromatids

    • Spindles disassemble

    • New nuclear envelopes form


Meiosis the cellular basis of sexual reproduction

그림 11.3 -3


Meiosis the cellular basis of sexual reproduction

그림 11.3 -4


Meiosis the cellular basis of sexual reproduction

그림 11.4 -1. 감수분열과 유사분열의 주요 단계 비교


Meiosis the cellular basis of sexual reproduction

그림 11.4 -2


Meiosis the cellular basis of sexual reproduction

그림 11.4 -3


Sex chromosomes in meiosis

Sex Chromosomes in Meiosis

  • Sex chromosomes

    • Different in males and females

    • Human females XX, males XY

    • XX fully homologous, XY homologous in short region


Sex chromosomes in meiosis1

Sex Chromosomes in Meiosis

  • Meiosis and sex chromosome inheritance

    • Gametes produced by females may receive either X chromosome

    • Gametes produce by males may receive either X or Y chromosome


11 2 mechanisms that generate variability

11.2 Mechanisms That Generate Variability (유전적 다양성)

  • Recombination depends on physical exchanges between homologous chromatids

  • Segregation of maternal and paternal chromosomes is random

  • Random joining of male and female gametes in fertilization adds additional variability


Recombination of chromatids

Recombination of Chromatids

  • Recombination (crossing over)

    • Key genetic shuffle of prophase I

  • Tetrads held together at synaptonemal complex (시냅시스 복합체)

    • Two of four chromatids exchange alleles

    • Chiasmata or crossovers are points of exchange


Meiosis the cellular basis of sexual reproduction

그림 11.5. 유전자 재조합을 완수한 염색분체 사이의 교환 효과


Meiosis the cellular basis of sexual reproduction

그림 11.6


Random segregation

Random Segregation

  • Random segregation

    • Key genetic shuffle of metaphase I

  • Each chromosome of a homologous pair may randomly end up at either spindle pole

    • Any combination of maternal and paternal chromosomes can be segregated to gametes

    • 2X number of possible combinations


Meiosis the cellular basis of sexual reproduction

그림 11.7. 중기I에서 3쌍의 염색체가 무작위로 방추사에 연결된 가능한 결과들


Random fertilization

Random Fertilization

  • Random chance of male and female gamete forming zygote

  • Meiosis allows randomness necessary for Mendelian laws of inheritance

    • Recombination, random segregation, and random fertilization are mechanisms of randomness


11 3 the time and place of meiosis in organismal life cycles

11.3 The Time and Place of Meiosis in Organismal Life Cycles (감수분열 시기와 장소)

  • In animals, diploid phase dominant and meiosis followed directly by gamete formation

  • In most plants and fungi, generations alternate between haploid and diploid phases

  • In some fungi and other organisms, haploid phase dominant and diploid phase single cell


Animal life cycles

Animal Life Cycles

  • Diploid phase dominates animal life cycles

    • Meiosis followed directly by gamete formation

    • Haploid phase is reduced and short, no mitosis

  • In males, all four nuclei from meiosis form separate sperm cells

  • In females, only one nucleus becomes an egg


Meiosis the cellular basis of sexual reproduction

그림 11.8. 진핵생물에서 감수분열 시기와 장소의 차이


Plants and fungi life cycles

Plants and Fungi Life Cycles

  • Alternation of generations

    • Alternate between haploid and diploid phase

  • Fertilization produces sporophytes (포자체)

    • Diploid individuals

  • Sporophytes produce haploid spores (meiosis)

    • Multicellular gametophytes (배우체) (mitosis)

    • Gametophytes produce gametes


Other fungi and algae life cycles

Other Fungi and Algae Life Cycles

  • In some organisms, diploid phase limited to single cell zygote

  • Zygote (접합자) undergoes meiosis

    • Mitosis only occurs in haploid cells

    • Gametes usually designated + or -


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