Pembelahan Sel II

Pembelahan Sel II : Meiosis

Reproduksi Seksual : Meiosis

Tjd pada sel gamet ( sel ovum & sel sperma) Meiosis mereduksi jumlah kromosom dr diploid

menjadi haploid Pembelahan sel tjd 2 kali 4 sel anak

memiliki kromosom setengah dr sel induk

Meiosis 1

Saat 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 1

MEIOSIS I: Homologous chromosomes separate

INTERPHASE PROPHASE I METAPHASE I ANAPHASE I

Centrosomes(withcentriolepairs)

Nuclearenvelope

Chromatin

Sites of crossing over

Spindle

Sisterchromatids

Tetrad

Microtubules attached tokinetochore

Metaphaseplate

Centromere(with kinetochore)

Sister chromatidsremain attached

Homologouschromosomes separate

Meiosis II

Meiosis 2 pada intinya sama dengan mitosis: Sister kromatid pada masing2 kromosom

b'pisah Menghasilkan 4 sel anak yg haploid

Meiosis II

MEIOSIS II: Sister chromatids separate

TELOPHASE IAND CYTOKINESIS PROPHASE II METAPHASE II ANAPHASE II

Cleavagefurrow

Sister chromatidsseparate

TELOPHASE IIAND CYTOKINESIS

Haploiddaughter cellsforming

Review: Perbandingan Mitosis & Meiosis

Figure 8.15

MITOSIS MEIOSIS

PARENT CELL(before chromosome replication)

Site ofcrossing over

MEIOSIS I

PROPHASE ITetrad formedby synapsis of homologous chromosomes

PROPHASE

Duplicatedchromosome(two sister chromatids)

METAPHASE

Chromosomereplication

Chromosomereplication

2n = 4

ANAPHASETELOPHASE

Chromosomes align at the metaphase plate

Tetradsalign at themetaphase plate

METAPHASE I

ANAPHASE ITELOPHASE I

Sister chromatidsseparate duringanaphase

Homologouschromosomesseparateduringanaphase I;sisterchromatids remain together

No further chromosomal replication; sister chromatids separate during anaphase II

2n 2n

Daughter cellsof mitosis

Daughter cells of meiosis II

MEIOSIS II

Daughtercells of

meiosis I

Haploidn = 2

n n n n

Review:Perbandingan Mitosis & Meiosis

Kejadian Mitosis Meiosis

Replikasi DNA Tjd 1 kali selama interfase sblm pembelahan nukleus dimulai

Tjd 1 kali selama interfase sblm meiosis 1 dimulai

Jumlah pembelahan 1 kali : Profase, metafase, anafase & telofase

2 kali, masing2 tmsk Profase, metafase, anafase & telofase

Sinapsis kromosom homolog

Tidak terjadi Tjd pd profase 1: kromosom homolog bergabung m'btk tetrad (kel.4 kromatid), tjd pindah silang (cross over)

Jumlah sel anak & komposisi genetik

2, masing2 diploid (2n), identik dgn sel indul

4, haploid, mengandung separuh jumlah kromosom sel induk, tdk identik dgn sel induk

Peran dlm tubuh Mjd organisme dewasa multiseluler, m'hsl sel utk pertumbuhan & perbaikan jaringan

M'hsl gamet , mengurangi jumlah kromosom separuh nya & tjd variabilitas genetik diantara gamet

MEIOSIS PADA MANUSIA

GOOD LUCK & ENJOY YOUR STUDY