Pembelahan Sel & Sistem Reproduksi

Cell division / Reproduksi Asexual Mitosis Menghasilkan sel dengan informasi sama identical daughter cells Selnya sama betul (exact copies) clones Jumlah DNA sama Jumlah chromosome sama Informasi genetik sama Peran : pertumbuhan dan perkembangan organisme Apa kebaikan reproduksi aseksual?

Pembelahan sel secara meiosis

How does corn make sperm & egg? reduce 20 chromosomes  10 chromosomes half the number of chromosomes 10 20 10 20 Egg nuclei 10 meiosis 20 10 fertilization Sperm nuclei

Meiosis: menghasilkan gamet Alternating processes, alternating stages chromosome number must be reduced diploid  haploid meiosis reduces chromosome number fertilization restores chromosome number haploid  diploid n  2n

Chromosome Homologous Chromosome Berpasangan Pasangan chromosome yang membawa gen sama Mengatur sifat bawaan yang sama homologous = sama informasi diploid 2n Chromosom homolog Pasangan ganda chromosom homolog

Making gametes for the next generation - 2 copies - diploid - 2n - 1 copy - haploid - 1n

Double division of meiosis Replikasi DNA 1st division of meiosis separates homologous pairs 2nd division of meiosis separates sister chromatids

Menjelang meiosis 1st step of meiosis Duplikasi DNA Why bother? meiosis evolved after mitosis convenient to use “machinery” of mitosis DNA disintesis pada fase S saat interphase MEIOSIS 2n = 6 single stranded 2n = 6 double stranded M1 prophase

2n = 4 single stranded Preparing for meiosis 1st division of meiosis separates homologous pairs 2n = 4 double stranded prophase1 2n = 4 double stranded metaphase1 synapsis telophase1 tetrad 1n = 2 double stranded

What does this division look like? Meiosis 2 2nd division of meiosis separates sister chromatids 1n = 2 double stranded What does this division look like? prophase2 1n = 2 double stranded metaphase2 1n = 2 single stranded telophase2

Steps of meiosis Meiosis 1 Meiosis 2 interphase prophase 1 metaphase 1 anaphase 1 telophase 1 Meiosis 2 prophase 2 metaphase 2 anaphase 2 telophase 2 1st division of meiosis separates homologous pairs (2n  1n) 2nd division of meiosis separates sister chromatids (1n  1n) * just like mitosis *

Mitosis vs. Meiosis

Mitosis vs. Meiosis Mitosis Meiosis 1 division daughter cells genetically identical to parent cell produces 2 cells 2n  2n produces cells for growth & repair no crossing over Meiosis 2 divisions daughter cells genetically different from parent produces 4 cells 2n  1n produces gametes crossing over

Pindah Silang (Crossing over) Selama Prophase 1 Bagian pasangan homolog berganda sister chromatid bersentuhan crossing over tetrad synapsis

Crossing over 3 steps Kombinasi sifat baru cross over (pindah silang) breakage of DNA (Pemutusan gugus DNA) re-fusing of DNA (Penyambungan gugus DNA) Kombinasi sifat baru

Pindah Silang Membentuk kombinasi sifat bawaan baru pada generasi berikutnya

Apa kelemahan reproduksi seksual? Atau ada pertanyaan ??