2014
CELL DIVISION - MEIOSIS
Výukový materiál MB 04 - 96Tvůrce: Mgr. Šárka Vopěnková
Tvůrce anglické verze: ThMgr. Ing. Jiří FollerProjekt: S anglickým jazykem do dalších předmětů
Registrační číslo: CZ.1.07/1.1.36/03.0005Tento projekt je spolufinancován ESF a SR ČR
sexual reproduction sexual cells = gametes gamete + gamete = zygote zygote > germ > adult individual gametes have got the half number of chromosomes 46 chromosomes > 2 sets each of 23 chromosome 2 sets of chromosomes = diploid cells one set of chromosomes = haploid cells
MEIOSIS
meiosis completes a special type of cell cycle, by which gametes develop
meiosis = gametogenesis interphase ( G1 , S phase a G2 phase) > meiosis: only one replication of DNA in S phase and two cell divisions followed quickly after each
other therefore - > originated cells are haploid meiosis = reducing division
MEIOSIS
a) first meiotic division = heterotypical reducing:
different from mitosis from 1 diploid cell develop 2 haploid cells b) second meiotic division = homeotypical: Identical with mitosis from 2 haploid cells develop 4 haploid cells
MEIOSIS
a) first meiotic division = heterotypical reducing: prophase: conserved nucleolus and nuclear membrane 2 sets of homological chromosomes pair homological chromosomes attach to each
other = synapsis ( „zip fastening“) pairs of connected homological chromosomes are
called bivalents
MEIOSIS
bivalents are four-thread formations= tetrads recombination process – crossing – over: reciprocal exchange of parts non-sister
chromatids, which are not genetically identical new combinations of gather and mother genes
develop synapsis ends by the isolation of homological
chromosomes
MEIOSIS
metaphase: equatorial plane ! division of centromeres does not happen > neither
chromosomes anaphase: reduction of the chromosome number > to the poles
travel whole, not divided two-chromatid chromosomes
random segregation of father and mother chromosomes > various combinations in gametes
MEIOSIS
telophase ……… b) second meiotic division= homeotypical: normal mitosis 2 haploid cells prophase, metaphase, anaphase, telophase 4 haploid cells originate
MEIOSIS
1) reduction of chromosome number 2) recombination of father and mother genes
by the process crossing – over 3) random meiotic segregation great genetic importance
MEIOSIS - SIMMARY
male (haploid) + female gamete (haploid) = diploid zygote by multiple division of the zygote ( = more
mitosis) the whole organism develops the most cells are diploid (multicellular
organisms) lower plants (non-vascular) + bacteria are
haploid
MEIOSIS
diversification of cells into different types all cells have the same, complete genetic
base they use only a part of the genetic
information by their specialisation
DIFFERENCIATION OF CELLS
Genetic schema of miotic division of cell nucleus: a – e heterotypical prophase – a) laptotene b) zygotene c) pachytene d) diplotene e) diakinesis f) heterotypical metaphase (bivalents attached to the threads of division spindle)g) heterotypical anaphase (bichromatide chromosomes from bivalents separate from each
other h) homeotypical prophase i) Homeotypical metaphase j) homeotypical anaphase j) (monochromatide daughter chromosomes go to the poles of the division spindle)
SOURCESSOURCES
CHALUPOVÁ-KARLOVSKÁ, Vlastimila. Obecná biologie: středoškolská učebnice : evoluce, biologie buňky, genetika : s 558 řešenými testovými otázkami. 2., opr. vyd. Olomouc: Nakladatelství Olomouc, 2010, 206 s. ISBN 978-807-1822-820
KUBIŠTA, Václav. Obecná biologie: úvodní učební text biologie pro 1. ročník gymnázií. 3. upr. vyd. Praha: Fortuna, c2000, 103 s. ISBN 80-716-8714-6.
ZÁVODSKÁ, Radka. Biologie buněk: základy cytologie, bakteriologie, virologie. 1. vyd. Praha: Scientia, 2006, 160 s. ISBN 80-869-6015-3
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