Meiosis Flashcards
What is Clonal Reproduction
A type of asexual reproduction in which parental organisms produce genetically identical individuals
What are haploid and diploid cells
Haploid (n) cells have 1 copy of all genetic information
Diploid cells (2n) have 2 copy’s of all genetic information (maternal, paternal)
Why is meiosis important in terms of diploid/haploid
Meiosis reduces cells from diploid number (2n) to haploid number (n) thus when 2 gametes fertilise, zygote has correct diploid (2n) number
If gametes were produced by mitosis, they would be 2n and hence offspring would be 4n
What are the stages of meiosis
Meiosis 1 - seperate the pair of homologous chromosomes and reduces the diploid cell to haploid (with duplicated chromosomes)
Meiosis 2 - devision of each of the haploid cells produced in meiosis 1
What are the phases of meiosis 1
Prophase 1
Metaphase 1
Anaphase 1
Telophase 1 and cytokinesis
What is prophase 1
Different from prophase of mitosis
Maternal and Paternal homologous chromosomes recognise each other, align, and synapse
Crossing over between non sister chromatids occurs at chiasmata
Mitotic spindle forms between two asters/centromeres that move to opposite ends of cell
Nuclear envelope disintegrates
What is crossing over
A process where two homologous non sister chromatids pair up with each other and exchange different segments of genetic material to form two recombinant chromosomes/sister chromatids
What is a chiasmata
The point of contact between two chromatids belonging to homologous chromosomes
What is metaphase 1
Pared homologous chromosomes move to metaphase plate
Chiasmata (not kinetochore, as in mitosis) line up on metaphase plate
Kinetochore microtubules connect to centromere (via kinetochore) of chromosome
Non Kinetochore microtubules connect to other non kinetochore microtubules of opposite pole
What is anaphase 1
Kinetochore microtubules shorten, and non Kinetochore microtubules lengthen (just as in mitosis)
Recombined homologous chromosomes seperate (disjoin, disjunct, disjunction)
Sister chromatids remain attached (as opposed to mitosis where sister chromatids seperate)
What is telophase 1 and cytokinesis
Haploid cells with duplicated chromosomes (the pair of sister chromatids) form
Haploid because only half genetic information that original cell had
Spindle apparatus begins to desintergrate
Cleavage furrow forms, separating cell in two
What are the phases of mitosis 2
Prophase 2
Metaphase 2
Anaphase 2
Telophase 2 and cytokinesis
What happens in prophase 2
The chromatin condenses into chromosomes
Mitotic spindle forms between 2 asters/centromeres that move to opposite poles of the cell
Nuclear membrane disintegrates
What happens in metaphase 2
The centromeres of the paired chromosomes align along metaphase plate (via kinetochore microtubules)
Non kinetochore microtubules attach to other non kinetochore microtubules of opposite pole
What happens in anaphase 2
Kinetochore microtubules shorten, separating sister chromatids (sister chromatids disjoint)
Non kinetochore microtubules elongate, pushing poles of cell apart
