Meiosis
- Created by: une-meduse
- Created on: 15-05-13 16:25
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- MEIOSIS 1
- Meiosis is a reduction division, the resulting daughter cells have half the original number of chromosomes
- They are known as haploid and can be used for sexual reproduction
- Each parent produces reproductive cells called gametes
- Gametes fuse together at fertilisation to produce a zygote
- Each parent produces reproductive cells called gametes
- They are known as haploid and can be used for sexual reproduction
- (Interphase)
- PROPHASE 1
- METAPHASE 1
- ANAPHASE 1
- TELOPHASE 1
- In most animal cells two new nuclear envelopes form
- One around each set of chromosomes at each pole and the cell divides by cytokineses
- There is usually a brief interphase and the chromosomes uncoil
- In plant cells the cell goes straight from anaphase 1 into meiosis 2 (mostly)
- There is usually a brief interphase and the chromosomes uncoil
- One around each set of chromosomes at each pole and the cell divides by cytokineses
- MEIOSIS 2
- This division is at right angles to meiosis 1
- PROPHASE 2
- METAPHASE 2
- The chromosomes arrange themselves on the equator of the spindle
- The chromosomes are attached to the spindle microtubules at the centromeres
- The chromatids of each chromosome are randomly assorted
- The chromosomes are attached to the spindle microtubules at the centromeres
- ANAPHASE 2
- The centromeres divide
- The chromatids are pulled to opposite poles by the spindle fibres
- The chromatids randomly segregate
- The chromatids are pulled to opposite poles by the spindle fibres
- TELOPHASE 2
- Nuclear envelopes reform around the haploid daughter nuclei
- In animals the two new cells now divide and give four haploid cells
- In plants a tetrad of four haploid cells is formed
- In animals the two new cells now divide and give four haploid cells
- Nuclear envelopes reform around the haploid daughter nuclei
- The centromeres divide
- The chromosomes arrange themselves on the equator of the spindle
- METAPHASE 2
- In most animal cells two new nuclear envelopes form
- The homologous chromosomes in each bivalent are pulled by the spindle microtubules to opposite poles
- Centromeres (The point on a chromosome by which it is attached to a spindle fiber during cell division) do not divide
- The chiasmata (the points at which non-sister chromatids with a bivalent join) separate
- Lengths of chromatid (The two threadlike strands) that have been crossed over remain with the chromatid that they have become attatched
- Chromatid - Each of the two threadlike strands into which a chromosome divides longitudinally during cell division. Each contains a double helix of DNA.
- Lengths of chromatid (The two threadlike strands) that have been crossed over remain with the chromatid that they have become attatched
- The chiasmata (the points at which non-sister chromatids with a bivalent join) separate
- Centromeres (The point on a chromosome by which it is attached to a spindle fiber during cell division) do not divide
- TELOPHASE 1
- Bivalents (the pair of joined homologous chromosomes) line up across equator of spindle and attach at centromeres
- Bivalents (the joined chromosomes) arrange randomly
- Each member of the homologous pair faces opposite poles
- Bivalents (the joined chromosomes) arrange randomly
- ANAPHASE 1
- Chromatin (the mass of genetic material composed of DNA and proteins) condenses and supercoils
- Chromosomes come together in homologous pairs to form a bivalent
- METAPHASE 1
- At interphase before mitosis 1 the DNA replicates
- As a result each chromosome consists of two identical sister chromatids (half the chromosome) joined at the centromere
- PROPHASE 1
- Meiosis is a reduction division, the resulting daughter cells have half the original number of chromosomes
- If a nuclear envelope has reformed, it breaks down again
- PROPHASE 2
- METAPHASE 2
- The chromosomes arrange themselves on the equator of the spindle
- The chromosomes are attached to the spindle microtubules at the centromeres
- The chromatids of each chromosome are randomly assorted
- The chromosomes are attached to the spindle microtubules at the centromeres
- ANAPHASE 2
- The centromeres divide
- The chromatids are pulled to opposite poles by the spindle fibres
- The chromatids randomly segregate
- The chromatids are pulled to opposite poles by the spindle fibres
- TELOPHASE 2
- Nuclear envelopes reform around the haploid daughter nuclei
- In animals the two new cells now divide and give four haploid cells
- In plants a tetrad of four haploid cells is formed
- In animals the two new cells now divide and give four haploid cells
- Nuclear envelopes reform around the haploid daughter nuclei
- The centromeres divide
- The chromosomes arrange themselves on the equator of the spindle
- METAPHASE 2
- The nuclolus disappears, chromosomescondense and spindles form
- PROPHASE 2
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