what is the purpose of mitosis & meiosis?
it maintains the number of chromosomes in cells of a species
what are the three things about somatic cells ?
- both can be mitotically dividing or G arrested cell
- makes up most tissues
3.diploid in humans
what are germ cells?
diploid specialized cell that go through meiosis to make gametes (egg/sperm) haploid
what is n ?
n is the number of chromosomes in 1 set
what is the 2 types of meiosis that happen ?
Meiosis I & Meiosis II
what generally happens in meosis I
separation of chromosome where 2n got to n
what generally happens in Meosis II
Seperation of sister chromosomes
how many duplication are in mitosis & meiosis?
1
what are the 4 major stages of Meosis I ?
(PMAT I)
Prophase I
Metaphase i
Anaphase I
Telophase I
what are the 5 substages of prophase
lazy police di diaseased
Lepotene
Zygotene
Pachytene
Diplotene
Diakinesis
what are the 4 steps in order at Prophase I : Leptotene?
- DNA duplicate ( sister chromotids)
2.chromsomes condense
3.centrioles go to oppsite poles - microtubules began extending
what are the 3 steps in order at Prophase I : Zygotene ?
- chromsomes look for homologous partner
- the homologous chromsomes synapsis (zipper) due to proteins
- they form tetrad/ bivalents
what is tetrad?
homologous chromosomes paired ( a group of 4 chromatids
what is bivalent
a group of 2 homologous chromsomes
what is between the homologous in a tetrad/bivalent ?
the synaptonemal complex
what are the 2 steps in order at Prophase I : Pachytene?
- the homologous chromosomes cross over
- genetic exchange occur
what facilitates exchange of DNA of the homologous chromsomes?
recombination nodules on synaptonemal complex
what are the 3 steps in order at Prophase I : Diplotene?
- synaptonemal complex dissolves
- the tetrad become visiable
- cross over points show as chiasmata
what is the point of a tetrad cross over?
for maternal & paternal exchange of information which can result in new allelic combinations
what are the 3 steps in order at Prophase I : Diakinesis?
- chromsomes thickin & shorten
- nuclear membrane breaks down
- spindle fibers attach to kinetochores
what happens at Metaphase I ?
the tetrad sister chromatids line up at the metaphase plate
what 2 things happen at Anaphase I ?
the tetrads get spilt up and moved to opposite poles and he chiasmata is no longer holding them together
what are the 3 steps in order at Telophase I ?
2.nuclear membrane reforms
3. Cytokinesis happens
4. 2 haploid daughter cells (n)
what is the difference of Metaphase I & Metaphase in mitosis ?
mitosis separates sister chromosomes
Meiosis metaphase 1 separates homologous chromosomes
