Meiosis and Reproduction Flashcards
reasons for cell proliferation (mitosis)
repair, maintenance, growth, asexual reproduction
reasons for cell proliferation (meiosis)
sexual reproduction
why do we need meiosis?
If our germline cells didn’t undergo meiosis, when the egg and sperm fuse, it would create a zygote with double the amount of chromosomes (92 for humans) and the organism will not survive because of too many chromosomes. Also, the amount of chromosomes doubles each generation.
Meiosis vs Mitosis interphase
Interphase is the same in mitosis and meiosis
Prophase I vs. II
Both: Nuclear membrane breaks down (if needed), chromosomes condense (if needed), microtubules form (if needed).
I: CROSSING OVER/ DNA RECOMBINATION
II: *If needed
metaphase I v.s II
Both: Chromosomes line up in center of cell
I: Line up by homologous pairs
II: Line up perpendicular to how they did in I and single file
Anaphase I v.s II
Both: Chromosomes are pulled to opposite sides of cells
I: REDUCTION OF CHROMOSOME #, homologous chromosomes are separated
II: sister chromatids are separated
Telophase (and cytokinesis) I v.s II
Both: Nuclear membrane (may) reform, chromosomes (may) decondense, cell cytoplasm divides.
I: *may, forms 2 genetically different haploid cells
II: forms 4 genetically different haploid cells
Meiosis
contains interphase, meiosis I, and meiosis II.
(G1, S, G2, Prophase I, Metaphase I, Anaphase I, Telophase and Cytokinesis I, Prophase II, Metaphase II, Anaphase II, Telophase and Cytokinesis II)
Binary Fission
Asexual reproduction in single-celled organisms.
nondisjunction
Failure of chromosomes to separate correctly during Anaphase I or II.
aneuploidy
an abnormal number of chromosomes is a cell RESULTING from nondisjunction. (trisomy, monosomy)
How can you tell if nondisjunction happened in meiosis 1 or 2?
Meiosis I: two gametes with an extra chromosome and two gametes missing a chromosome
Meiosis II: one gamete with an extra chromosome, one gamete missing a chromosome, and two gametes with normal chromosomes.
