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10 Cards in this Set
- Front
- Back
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Meiosis occurs in any life cycle that involves sexual reproduction. |
meiosis reduces the chromosome number of a cell from diploid (2n) to haploid (n). |
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At the start of meiosis, the parental cell has the diploid number of chromosomes (4) |
meiosis requires two cell divisions, meiosis I and meiosis II the four daughter cells have the haploid number of chromosomes. DNA replication occurs prior to meiosis I. |
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Homologous |
about the same size contains the same types of genes in the same location |
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Meiosis, which requires two nuclear divisions, results in four daughter nuclei, each having one of each kind of chromosome and therefore half the number of chromosomes as the parental cell. |
the daughter cells mature into gametes (sex cells—sperm and egg) the homologous chromosomes come together and line up side by side. This process is called synapsis and it results in an association of four chromatids that stay in close proximity during the first two phases of meiosis I |
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Metosis I |
Prophase I: ~align with their homologous pairs (synapsis occurs) ~ match up and crossing over occurs (transfer genetic info and exchange between each other) make recombinants chromosomes. crossing-over is represented by an exchange of color between the chromosomes. |
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Metaphase I: Align up in the middle but in homologous pairs |
Anaphase I: the chromosomes move apart |
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Telophase I: end up with 2 cells The period of time between meiosis I and meiosis II is called interkinesis. Because the chromosomes are already duplicated, there is no replication of DNA during interkinesis. The daughter cells of meiosis I then proceed directly into meiosis II. |
Independent assortment occurs when these homologous pairs separate from each other during anaphase I, generating cells with different combinations of maternal and paternal chromosomes. |
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Meosis 2 |
Prophase 2: chromosome and spindle starting to form not more croosing over. cells have one chromosome from each homologous pair |
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metaphase 2: align in the middle but this time they are single |
Anaphase 2: chromatids pull apart |
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telophase 2: the 2 cells divide ending with 4 cells crossing over processes, males sperm leads to variety |
nondisjunction: chromosome not separate correctly (more or less) leading to genetic dissorders |
