meiosis
DESCRIPTION
Meiosis. Gamete Production. Meiosis. Similar in many ways to mitosis Several differences however Involves 2 cell divisions Results in 4 cells with 1/2 the normal genetic information. Vocabulary: Diploid (2N) - Normal amount of genetic material - PowerPoint PPT PresentationTRANSCRIPT
Gamete ProductionGamete Production
1
MeiosisMeiosisSimilarSimilar in many ways to in many ways to mitosismitosis
Several differences howeverSeveral differences howeverInvolves Involves 2 cell divisions2 cell divisionsResults in Results in 4 cells 4 cells with with 1/2 the 1/2 the normal genetic information.normal genetic information.
Vocabulary:Vocabulary:Diploid (2N) Diploid (2N) - Normal amount - Normal amount of genetic materialof genetic material
Haploid (N)Haploid (N) - 1/2 the genetic - 1/2 the genetic material.material.
2
MeiosisMeiosisMeiosis results in the Meiosis results in the formation of formation of
haploid cellshaploid cells..In Humans, these are the In Humans, these are the OvaOva (egg) and (egg) and spermsperm..
Ova are produced in the Ova are produced in the ovariesovaries in in femalesfemales
Process is called Process is called oogenesisoogenesisSperm are produced in the Sperm are produced in the testestestes of males.of males.
Process is called Process is called spermatogenesisspermatogenesisMeiosis occurs in 2 phases: Meiosis occurs in 2 phases: Meiosis IMeiosis I
& & Meiosis IIMeiosis II
3
Spermatogenesis & Spermatogenesis & OogenesisOogenesis
4
Sperm Sperm formatiformati
onon
Egg Egg formatiformati
onon
Meiosis IMeiosis IPrior to division (Prior to division (S phaseS phase), amount of ), amount of DNA doublesDNA doubles
5
Metaphase IMetaphase IDuring Metaphase Metaphase
II homologous homologous chromosomes chromosomes line-up along the metaphase plate or EQUATOREQUATOR
Areas of homologous chromosomes connectconnect at areas called CHIASMATACHIASMATA
Genes are Genes are exchanged at exchanged at these these connectionsconnections
6
Crossing OverCrossing OverSegments of Segments of
homologous homologous chromosomes chromosomes breakbreak and reattach and reattach at similar at similar locations.locations.
Results in Results in new new genetic genetic combinations combinations of of offspring.offspring.
This is the main This is the main advantage of advantage of sexual sexual reproductionreproduction
7
8
Anaphase IAnaphase IDuring Anaphase I, each During Anaphase I, each
HOMOLOGOUS HOMOLOGOUS CHROMOSOMECHROMOSOME is pulled is pulled to opposite sides of the to opposite sides of the cell.cell.
Unlike mitosis, the Unlike mitosis, the CENTROMERES DO NOT CENTROMERES DO NOT BREAKBREAK..
Nuclei MAY OR MAY NOT Nuclei MAY OR MAY NOT reform following division.reform following division.
CYTOKENESISCYTOKENESIS may or may or may not occur.may not occur.
9
Meiosis IIMeiosis IIDNA DNA DOES NOT DOES NOT doubledoubleChromosomes randomly line-Chromosomes randomly line-
up along metaphase plate like up along metaphase plate like regular mitosis.regular mitosis.
During During Anaphase II, Anaphase II, CENTROMERES BREAK CENTROMERES BREAK and and each each SISTER CHROMATID SISTER CHROMATID is is pulled to opposite sides of the pulled to opposite sides of the cell.cell.
Nuclei reform Nuclei reform and and cytokinesiscytokinesis usually occurs usually occurs (although it is often unequal).(although it is often unequal).
Sister chromatids10
Overview of MeiosisOverview of Meiosis
11
12