Meosis (lecture 11) Flashcards
What are the functions of meiosis
Reduce the number of chromosomes of the parent cell by half and produce 4 gametes
How do most organisms reproduce ? What does this process involve
Most organisms reproduce by sexual reproduction.
A process that involves meiosis: the formation of gametes ( eggs and sperm )
Compare mitosis and meiosis
Meosis is similar to mitosis but the result is completely different
They use the same terminology
At conception what do we get? What happens during meiosis
We get 1 complete set of chromosomes from dad and 1 complete set of chromosomes from mom
During meiosis the number of pairs of Chromosomes is reduced, from 2 pairs to1 pair in gametes
Meosis vs mitosis
Meiosis: ensures that when gametes are form, each gametes gets 1 complete of chromosomes ( not both sets)
Mitosis: ensures that every cell gets an exact copy of an individual’s complete genetic information
Why is meiosis necessary
To keep the number of chromosomes constant in successive generations
Without it there would be a doubling of chromosomes number every generation
Diploids cells (2n)
Cells that have the full genetic component
- 23 pair of chromosomes in humans
What does involve sexual reproduction ? What about the life cycle of sexual reproducing organisms ?
The fusion of gametes (fertilization ) to produce a diploid zygote
The life cycle involves the alternation of haploid and diploid stages
How are called cells that undergo Meiosis in animals ? What do they do
Germ-line cells (2n) that undergo Meosis to produce gametes (n)
- they give rise to eggs and sperm
How does meiosis occurs
The cell undergoes two sets of cell division :
Meiosis 1:
Prophase 1
Metaphase 1
Anaphase 1
Telophase 1
Interkinesis ( results in 2 diploid cells )
Meiosis 2
Prophase 2
Metaphase 2
Anaphase 2
Telophase 2
Cytokinesis ( results in 4 Daughter cells )
What are homologous chromosomes
Two chromosomes in a pair containing the same linear sequence of genes
Interphase in Meiosis
G1, S, G2 events just like in mitosis
-DNA is copied prior to meiosis 1 (sister chromatids)
Prophase 1
Very similar to prophase of mitosis
DNA coils and chromosomes become visible
Nuclear membrane, nucleolus disappears
Spindle apparatus forms
And centrioles are at opposite sides of the cell
Crossing over between non sister chromatids
Metaphase 1
Different from mitosis
Microtubules from opposite poles attach to each homologue (not sister chromatids)
Homologues are aligned at the metaphase plate side by side
Difference in chromosomes alignment between mitosis and meiosis
In Meosis, homologues are held together by chiasmata and the kinetchores of sister chromatids fuse and function as one
