Meiose 2015 capítulo 14
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Transcript of Meiose 2015 capítulo 14
Meiose
Professora RaquelCED 416 – Santa Maria
Maio 2015
MeioseUma célula diploide forma célula haploide
Meiose: Divisão em duas partes
Homólogos se separam
Cromátides-irmãsse separam
haploide
Meiose I
MeioseII
Diploide
Haploide
Divisão reducionalDivisão equacional
4 cromossomos
2 cromossomos 2 cromossomos
Meiose animal forma GametesMeiose tem tem que reduzir o número de
cromossomos pela metadeA fertilização restaura o número 2n
da mãe Do pai criança
demais!
O número certo!
Interfase
Meiose: prófase I
Fim
Meiose I: Divisão reducional
Núcleo Fibras de fuso Envelopenuclear
Profase I(Cromossomo duplicado)
Profase I
Metafase I Anafase I Telofase I (haploide)
Profase I
Início da profasePar de homólogos .Crossing over ocorre.
Fim da profaseCromosomos se condensam.Spindle forms.Envelope nuclear se fragmenta.
Cromossomos duplicados
Homólogos (mesmos genes, diferentes alelos)
Cromátides-irmãs(mesmos genes,mesmos alelos)
Gene X
Homólogos se separam na meiose I e então diferentes alelos se separam.
Tétrades se formam na Profase I
Cromossomos homólogos (cada um com suas cromátides)
Unem-se para formar a TÉTRADE
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Crossing-OverHomologous
chromosomes in a tetrad cross over each other
Pieces of chromosomes or genes are exchanged
Produces Genetic recombination in the offspring
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Homologous Chromosomes During Crossing-Over
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Crossing-over multiplies the already huge number of different gamete types produced by independent assortment
Crossing-Over
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Metaphase I
Homologous pairs of chromosomes align along the equator of the cell
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Anaphase I
Homologs separate and move to opposite poles.
Sister chromatids remain attached at their centromeres.
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Telophase I
Nuclear envelopes reassemble.
Spindle disappears.
Cytokinesis divides cell into two.
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Meiosis II
Only one homolog of each chromosome is present in the cell.
Meiosis II produces gametes with one copy of each chromosome and thus one copy of each gene.
Sister chromatids carry identical genetic information.
Gene X
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Meiosis II: Reducing Chromosome Number
Prophase IIMetaphase II
Anaphase IITelophase II
4 Genetically Different haploid cells
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Prophase II
Nuclear envelope fragments.
Spindle forms.
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Metaphase II
Chromosomes align along equator of cell.
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Anaphase II
Sister chromatids separate and move to opposite poles.
Equator
Pole
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Telophase IINuclear envelope assembles.
Chromosomes decondense.
Spindle disappears.
Cytokinesis divides cell into two.
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Results of MeiosisGametes (egg & sperm) form
Four haploid cells with one copy of each chromosome
One allele of each gene
Different combinations of alleles for different genes along the chromosome
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Meiosis Animation
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