Pembelahan Sel II : Meiosis

Reproduksi Seksual : Meiosis

Tjd pada sel gamet ( sel ovum & sel sperma)

Meiosis mereduksi jumlah kromosom dr diploid menjadi haploidPembelahan sel tjd 2 kali 4 sel anak memiliki kromosom setengah dr sel induk

Meiosis 1Saat tjd pembelahan pertama (meiosis 1), kromosom homolog berpasangan

Selama kromosom homolog b'pasangan terjadi pertukaran genetik (CROSS OVER)

Pasangan kromosom homolog b'pisah & menghasilkan 2 sel anak

Meiosis 1MEIOSIS I: Homologous chromosomes separate

INTERPHASECentrosomes (with centriole pairs)

PROPHASE I

METAPHASE IMicrotubules attached to kinetochore

ANAPHASE I

Sites of crossing over Spindle

Metaphase plate

Sister chromatids remain attached

Nuclear envelope

Chromatin

Sister chromatids

Tetrad

Centromere (with kinetochore)

Homologous chromosomes separate

Meiosis IIMeiosis 2 pada intinya sama dengan mitosis:

Sister kromatid pada masing2 kromosom b'pisahMenghasilkan 4 sel anak yg haploid

Meiosis IIMEIOSIS II: Sister chromatids separate TELOPHASE I AND CYTOKINESIS PROPHASE II METAPHASE II ANAPHASE II TELOPHASE II AND CYTOKINESIS

Cleavage furrow

Sister chromatids separate

Haploid daughter cells forming

Review: Perbandingan Mitosis & MeiosisMITOSIS PARENT CELL (before chromosome replication) PROPHASE Duplicated chromosome (two sister chromatids) Chromosome replication 2n = 4 Chromosome replication MEIOSIS Site of crossing over MEIOSIS I PROPHASE I Tetrad formed by synapsis of homologous chromosomes

METAPHASE

Chromosomes align at the metaphase plate

Tetrads align at the metaphase plate

METAPHASE I

ANAPHASE TELOPHASE

Sister chromatids separate during anaphase

Homologous chromosomes separate during anaphase I; sister chromatids remain together

ANAPHASE I TELOPHASE I

Haploid n=2 Daughter cells of meiosis I

2n Daughter cells of mitosis

2n

No further MEIOSIS II chromosomal replication; sister chromatids separate during n n n n anaphase II Daughter cells of meiosis II

Figure 8.15

Review: Perbandingan Mitosis & MeiosisKejadianReplikasi DNA

MitosisTjd 1 kali selama interfase sblm pembelahan nukleus dimulai 1 kali : Profase, metafase, anafase & telofase Tidak terjadi

MeiosisTjd 1 kali selama interfase sblm meiosis 1 dimulai 2 kali, masing2 tmsk Profase, metafase, anafase & telofase Tjd pd profase 1: kromosom homolog bergabung m'btk tetrad (kel.4 kromatid), tjd pindah silang (cross over) 4, haploid, mengandung separuh jumlah kromosom sel induk, tdk identik dgn sel induk M'hsl gamet , mengurangi jumlah kromosom separuh nya & tjd variabilitas genetik diantara gamet

Jumlah pembelahan Sinapsis kromosom homolog

Jumlah sel anak & komposisi genetik Peran dlm tubuh

2, masing2 diploid (2n), identik dgn sel indul Mjd organisme dewasa multiseluler, m'hsl sel utk pertumbuhan & perbaikan jaringan

MEIOSIS PADA MANUSIA

GOOD LUCK & ENJOY YOUR STUDY