This is a draft cheat sheet. It is a work in progress and is not finished yet.
Meiosis
Meiosis is a type of cell division |
Takes place in the reproductive organs |
Cells that divide are Diploid to start with |
Cells formed from meiosis are Haploid |
These cells have Half the chromosome number |
Daughter Cells Genetically Different |
Before the Start of Meiosis
DNA unravels and Replicates two Chromosomes called Chromatids |
2 Sister Chromatids are joined in the center by the Centromere |
Meiosis 1 - the chromosomes arrange into Homologous Pairs |
Homologous Pairs Seperate halving the Chromosome number |
This is Meiosis 1 |
Meiosis II
Sister Chromatids are separated |
The Centomere is divided |
Chromatids are now chromosomes |
4 Haploid cells are produced |
Homologous Chromosomes
Maternal and Paternal Chromosomes |
Paired together |
chromosomes are same size and carry same genes |
The Different versions of those genes called Alleles |
These pairs of Chromosomes are called Homologous Chromosomes |
Gametes
Meiosis is used to produce Gametes |
Sex Cells, Sperm or Egg cells |
These Cells fuse in fertilization to form a Zygote |
Needs Half as many Chromosomes as normal Cell |
Diploid cell --- Haploid Cell |
How DNA is passed on to generation |
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Phases of Meiosis
Interphase 1 |
Prophase 1 |
Metaphase 1 |
Anaphase 1 |
Telophase 1 |
Prophase 2 |
Metaphase 2 |
Anaphase 2 |
Telophase 2 |
2 Main Events that lead to genetic variation
Crossing over chromatids |
Independent segregation of chromosomes |
Crossing over Chromatids
In meiosis 1 homologous pair of chromosomes pair up |
Bits of Chromatids swap over |
Chromatids swap alleles |
Different sets of alleles increase genetic variation |
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Independent segregation of Chromosomes
Homologous pairs of chromosomes, one from mother, one from father |
Maternal and Paternal Chromosomes |
Homologous pairs are sepereated, its random which chromosome end up in each daughter cell |
Potential for different combinations |
Independent Segregation of Chromosomes |
Genetic Variation in offspring |
223 Potential variation for human chromosomes |
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