Meiosis the cellular basis of sexual reproduction
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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

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
11.1 The Mechanisms of Meiosis 정렬된다

  • 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 정렬된다

  • 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 정렬된다

  • Fertilization fuses nuclei of egg and sperm

    • Zygote (접합자) cell produced by fertilization

    • Restores parental chromosome number


Homologous chromosome pairs
Homologous Chromosome Pairs 정렬된다

  • 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)


그림 정렬된다11.1. 감수분열의 주기와 수정


Meiotic cell cycle
Meiotic Cell Cycle 정렬된다

  • 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 정렬된다

  • Meiosis I: First meiotic division

    • Recombination exchanges segments between homologues

    • Produces two haploid cells with chromatids attached


Meiosis ii
Meiosis II 정렬된다

  • Meiosis II: Second meiotic division

    • Sister chromatids separate into separate cells

    • Produces 4 recombined haploid cells


그림 정렬된다11.2. 두번의 감수분열에 의한 4개의 반수체 핵의 생산


Meiotic cell cycle 1
Meiotic Cell Cycle (1) 정렬된다

  • 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)


그림 정렬된다11.3 -1. 감수분열


Meiotic cell cycle 2
Meiotic Cell Cycle (2) 정렬된다

  • 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


그림 정렬된다11.3 -2


Meiotic cell cycle 3
Meiotic Cell Cycle (3) 정렬된다

  • 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


그림 정렬된다11.3 -3


그림 정렬된다11.3 -4


그림 정렬된다11.4 -1. 감수분열과 유사분열의 주요 단계 비교


그림 정렬된다11.4 -2


그림 정렬된다11.4 -3


Sex chromosomes in meiosis
Sex Chromosomes in Meiosis 정렬된다

  • 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 정렬된다

  • 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 정렬된다(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 정렬된다

  • 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


그림 정렬된다11.5. 유전자 재조합을 완수한 염색분체 사이의 교환 효과


그림 정렬된다11.6


Random segregation
Random Segregation 정렬된다

  • 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


그림 정렬된다11.7. 중기I에서 3쌍의 염색체가 무작위로 방추사에 연결된 가능한 결과들


Random fertilization
Random Fertilization 정렬된다

  • 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 정렬된다 (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 정렬된다

  • 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


그림 정렬된다11.8. 진핵생물에서 감수분열 시기와 장소의 차이


Plants and fungi life cycles
Plants and Fungi Life Cycles 정렬된다

  • 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 정렬된다

  • 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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