reproduksi sel
TRANSCRIPT
REPRODUKSI SEL
Reproduksi protista berbeda dengan sel hewan lainnya
Jamur → spora
Tanaman → biji
Hewan → telur
Protista → sel tunggal
Sel anak → mempunyai membran, sitoplasma dan inti
Inti mengandung DNA yang identik
Salah satu protista adalah amoeba
Amoebas → sangat tipis, membran sel fleksibel
Bergerak dengan menjulurkan sitoplasma keluar membran dan membentuk pseudopods ("false feet")
Di dalam sel terdapat ruang sbg organ percernaan
REPRODUKSI SEL
MITOSIS → sel somatikMEIOSIS → sel seks atau gamet
(spermatozoa dan ovum)
MITOSIS
Interfase Profase Metafase AnafaseTelofase
1. Terjadi sintesis protein; kromatin dan inti nampak jelas; replikasi DNA
2. Kromatin tebal → kromosom; membran inti melebur; sentriol bergerak pada sisi yang berlawanan dan serabut spindel mulai terbentuk
3. Kromosom yang dihubungkan spindel ada di tengah
4. Kromosom memisah menuju ke kutub yang berlawanan
5. Kromosom kembali berbentuk kromatin; speindel melebur; membran inti nampak; sentriol replikasi; terbentuk membran sel baru
Cell ReproductionInterphase (before Mitosis) Early Prophase Prophase Late Prophase Transition to Metaphase Metaphase Anaphase Telophase
MEIOSIS :
Terdiri dari 2 fase :• Meiosis I : merupakan pembelahan yang memisahkan 2
kromosom homolog (kromatid), terjadi reduksi
kromosom• Meiosis II : merupakan pemisahan kromatid melalui
pembelahan sentromer.
Hasilnya : sel diploid menghasilkan 4 sel
anakan yang haploid
Tahap-tahapnya sbb :
PROPHASE I
SYNAPSIS - the pairing and bonding together of homologous chromosomes to form tetrads
Homologous chromosomes consist of one maternal and one paternal chromosome
PROPHASE I
CROSSING-OVER: Exchange of chromatid
segments within tetrads to produce new allele combinations
Nonsisters cross over, break, and rejoin
Increases genetic variety
VIEW OF NUCLEUSAND TETRADS
CROSSING -OVER
Notice the exchange of segments that has happened in two places on the larger homologous pair
This is crossing over
METAPHASE I
Tetrads line up in the middle of the cell in a straight line at equator
Spindle fibers attach to only 1 kinetochore of each centromere
ANAPHASE I
Tetrads are separated as homologous chromosomes are pulled to opposite poles of the cell
(Remember: the chromosomes are still actually sister chromatids)
TELOPHASE I
Cytokinesis may occur and two HAPLOID cells containing sister chromatids are produced
A brief period of interkinesis occurs
INTERKINESIS
TELOPHASE IA short interphaselike stage between divisions
PROPHASEII
MEIOSIS
Fase I
Fase II
SEPARATES SISTER CHROMATIDS
PROPHASE II Nuclear membranes disappearNucleoli disappearSpindle fibers formChromatin coils to form chromosomesWhat does this remind you of ?Prophase II is basically the same as
mitosis prophase x 2
METAPHASE II
In metaphase II the two cells line up their chromosomes in the middle of the cell in a straight line at equator
Again this is the same as mitosis metaphase - only two cells are doing it
Each cell is doing it with only 1 chromosome of each kind, not pairs
ANAPHASE II
During this phase the centromeres of the chromosomes in the two cells divide and sister chromatids move to opposite poles of the cells
Very mitosis-like again
TELOPHASE II
Final act of meiosis Nuclear membranes reappearNucleoli reappearChromosomes uncoil to chromatin Spindle fibers disappearCytokinesis occurs to produce a total of 4
haploid cells (N)
Meiosis : Summary of reduction division
Phases of spermatogenesis (i.e., meiosis in males)