ch. 11 meiosis and sexual reproduction Flashcards
what does meiosis produce?
haploid gametes that contain half of the chromosomes of diploid somatic cells
how many gametes will one diploid germ produce through meiosis?
4
what is a zygote?
the 2N/diploid created from fertilization
what happens during prophase 1?
-replicated chromosomes coil tighter
-nuclear envelope dissolves
-homologues undergo synapsis
-crossing over occurs between non-sister chromatids
what is synapsis?
when the homologous chromosomes line up across from each other following replication
what is the synaptonemal complex?
where proteins between the homologues are held
what is crossing over?
genetic recombination between non-sister chromatids (physical exchange of regions between the homologues)
what is the chiasmata?
the sites of crossing over
what happens during metaphase I?
-terminal chiasmata hold homologues together after crossing over
-microtubules from opposite poles attach to each homologue
-homologues align at the metaphase plate across from one another
-the distribution of each pair of homologues on the metaphase I plate is random (random or independent assortment)
-pairs of homologues randomly assort and align opposite one another along the metaphasic plate
-microtubules from each pole attach to the kinetochores of homologues in their half of the cell
what happens during anaphase I?
-microtubules of the spindle shorten
-homologues are separated from each other
-sister chromatids remain attached to one another at their centromeres
what happens during telophase I?
-nuclear envelopes form around each set of chromosomes
-each new nucleus is now haploid
-sister chromatids are no longer identical because of crossing over
what happens during prophase II?
nuclear envelopes dissolve and spindle apparatus forms
what happens during metaphase II?
sister chromatids align on metaphase plate (cohesin on the metaphasic plate)
what happens during anaphase II?
sister chromatids separate
what happens during telophase II?
nuclear envelope reforms; cytokinesis follows
what happens After crossing over in the early stages of meiosis I?
the homologues separate from one another in anaphase I
Meiosis is distinguished from mitosis by:
- Synapsis and crossing over in meiosis I
- Sister chromatids remain joined at their centromeres in meiosis I
- Kinetochores of sister chromatids attach to the same pole in meiosis I
- DNA replicates once, but cell divides twice
what do genetic differences arise from?
1) crossing over in meiosis I
2) random or independent assortment of homologues in metaphase I
how many chromosomes do mosquitoes have?
6
how many chromosomes do fruit flies have?
8
how many chromosomes does garlic have?
16
how many chromosomes does a mouse have?
40
how many chromosomes does a red vischacha rat have?
102
how many chromosomes does an atlas blue butterfly have?
448
what is unique about meiosis in plants?
have an alternation of multicellular generations with both multicellular diploid (2N) and multicellular haploid (1N) stages. This is a haplodiplontic life cycle
