MeiosisThe Continuation of Life
Meiosis: The Continuation of Life
Homologous ChromosomesPaired chromosomes
One from each parent
Genes for same traitAllelesSame order on chromosome
Diploid vs. HaploidDiploid Cell that has TWO of each kind of chromosome (parent)2n
Haploid Cell that has ONE of each kind of chromosome1n
QuestionWhat would happen if Mitosis was the only way our cells could divide?
23pairs 46pairs 96pairsetc.
We need a way to divide the Chromosome # in half! What is this called??Meiosis!
MeiosisPurpose make haploid cells
Phases of MeiosisMeiosis I
Prophase IMetaphase IAnaphase ITelophase I
Prophase IIMetaphase IIAnaphase IITelophase IICytokinesis
Prophase ISame as in MitosisBut
Homologous Chromosomes find each other
Crossing over occurs
Exchange of Genetic material
Crossing OverCrossing Over and its products!
Metaphase IHomologous pairs line up
Tetrads still together
Anaphase IHomologous Chromosomes separate
Telophase IJust like Telophase in MitosisChromosomes unwindNuclear membrane forms
Meiosis IIJust like Mitosis!!
Meiosis IIProphase IIMetaphase IIAnaphase IITelophase II
Prophase IIChromosomes appearCentrioles migrateSpindle fibers
Metaphase IIChromosomes line upLike mitosis
Anaphase IIChromosomes separate like in mitosisMove to ends of cell
Telophase IINuclear membrane formsChromatids unwind Chromatin
ProductsFrom single diploid (2N) 4 Haploid (1N)
Cellsalive!Meiosis: An Interactive Animation
Web Lesson Meiosis
Mitosis vs. Meiosis
GametesWhy are some of the chromosomes different colors?
VariationGenetic Variation is provided by meiosis
Because of assortment 70 trillion possibilities
Crossing Over increases that numberReason for great variety of people
Mistakes in MeiosisNondisjunction the failure of homologous chromosomes to separate properly
Trisomy 1 extra chromosomeMonosomy 1 less chromosomePolyploidy extra set of all chromosomes
TrisomyTrisomy 21Downs Syndrome
Shorter than normal
MonosomyUsually lethal but, but not in
Look at KaryotypeWhat is wrong here?
PolyploidyWhole extra set of chromosomes(3n) or (4n)
Death animal zygotes
Often occurs in plantsBigger and Healthier
QuestionWhat separates during Meiosis I?
QuestionWhat type of cell results from meiosis I?
QuestionWhat separates during Meiosis II?