MEIOSISMEIOSIS

LINDA HEIDENRICHBIOLOGY

LINDA HEIDENRICHBIOLOGY

ALL ABOUT MEIOSISALL ABOUT MEIOSIS

Occurs in sex organs (testes and ovaries)

Cuts the chromosome number in halfHas two stages: Meiosis I and Meiosis IIFollows PMATEntire process preceded by INTERPHASE

and succeeded by CYTOKINESIS

Occurs in sex organs (testes and ovaries)

Cuts the chromosome number in halfHas two stages: Meiosis I and Meiosis IIFollows PMATEntire process preceded by INTERPHASE

and succeeded by CYTOKINESIS

PROPHASE IPROPHASE I

Just like mitosisNuclear envelope disintegratesChromosomes become visible and

pair with homologous chromosomes to form a tetrad

Spindle fibers appear

Just like mitosisNuclear envelope disintegratesChromosomes become visible and

pair with homologous chromosomes to form a tetrad

Spindle fibers appear

METAPHASE IMETAPHASE I

Homologous chromosomes align at the center of the cellhttp://en.wikipedia.org/wiki/Meiosis

Homologous chromosomes align at the center of the cellhttp://en.wikipedia.org/wiki/Meiosis

ANAPHASE IANAPHASE I

Homologous chromosomes move to opposite poles of the cellhttp://en.wikipedia.org/wiki/Meiosis

Homologous chromosomes move to opposite poles of the cellhttp://en.wikipedia.org/wiki/Meiosis

TELOPHASE I TELOPHASE I

Nuclear membranes reformSpindle fibers disappear

DIFFERENCE: Chromosomes remain visiblehttp://en.wikipedia.org/wiki/Meiosis

Nuclear membranes reformSpindle fibers disappear

DIFFERENCE: Chromosomes remain visiblehttp://en.wikipedia.org/wiki/Meiosis

MEIOSIS II (MITOSIS)MEIOSIS II (MITOSIS)

REVIEW:Prophase: Nuclear envelope disappears,

spindle fibers formMetaphase: Chromosomes align in the

center of the cellAnaphase: Sister chromatids separate to

different poles of the cellTelophase: Nuclear envelope reforms,

spindle fibers disappear, chromosomes become invisible

REVIEW:Prophase: Nuclear envelope disappears,

spindle fibers formMetaphase: Chromosomes align in the

center of the cellAnaphase: Sister chromatids separate to

different poles of the cellTelophase: Nuclear envelope reforms,

spindle fibers disappear, chromosomes become invisible

NONDISJUNCTIONNONDISJUNCTION

Term for what happens when homologous chromosomes or sister chromatids fail to split.

Leads to trisomy (extra chromosome) or monosomy (too few chromosomes)http://en.wikipedia.org/wiki/Nondisjunction http://en.wikipedia.org/wiki/Down_syndrome

Term for what happens when homologous chromosomes or sister chromatids fail to split.

Leads to trisomy (extra chromosome) or monosomy (too few chromosomes)http://en.wikipedia.org/wiki/Nondisjunction http://en.wikipedia.org/wiki/Down_syndrome