Chapter 11 - Sexual Reproduction and Meiosis Flashcards
Meiosis is a form of cell division that leads to the production of ________.
gametes
Gametes:
egg cells and sperm cells; contain 1/2 the number of chromosomes of an adult body cell (haploid)
Somatic cells:
adult body cells; diploid
Sexual reproduction includes the fusion of gametes (____________) to produce a diploid _________.
fertilization; zygote
How many rounds of division are included in meiosis?
2: Meiosis I and Meiosis II
Synapsis
Homologous chromosomes become closely associated with each other.
Synaptonemal complex
protein structure that forms between homologous chromosomes during meiosis
Genetic recombination between non-sister chromatids; physical exchange of regions of the chromatids
crossing over
Chiasmata
sites of crossing over
Why is there a reduction of the chromosome number from diploid to haploid after meiosis?
Meiosis involves two successful cell divisions with NO replication of genetical material between them.
Prophase I:
- chromosomes coil tighter and become more visible
- nuclear envelope dissolves
- homologues become closely associated in synapsis
- crossing over between non-sister chromatids
Metaphase I:
-microtubules from opposite poles attach to each homologue
-homologues are aligned at the metaphase plate side-by-side
[the orientation of each pair of homologues on the spindle is random(independent assortment)]
Anaphase I:
microtubules of the spindle shorten, thus pulling the homologues away from each other
Telophase I:
nuclear envelopes form around each set of chromosomes
[each new nucleus is now haploid and sister chromatids are no longer identical bc of crossing over]
Prophase II:
nuclear envelopes dissolve and spindle apparatus forms
