Meiosis Flashcards
(22 cards)
Synapsis
during early prophase 1 homologous chromosomes become “zipped up”
synaptonemal complex
proteins responsible for “zipping up” chromosomes
Crossing over
genetic recombination btwn non sister chromatids
chiasmata
site of crossing over, contact maintained until anaphase 1
Steps of crossing over
- ) condensation
- ) synapsis
- ) crossing over and chiasmata formation
- ) partial separation of homologs
Prophase I
chiasmata present
Prometaphase I
spindles attach to kinetochores on chromosomes
Metaphase I
homologous pairs line up in center
Anaphase I
homologous chromosomes separate, but sister chromatids don’t
Telophase I & Cytokinesis
daughter cells ready for prophase II
Prophase II
nuclear envelop breaks down, chromosomes condense
Prometaphase II
spindles attach to kinetochores on chromosomes
Metaphase II
chromosomes align in center of cell
Anaphase II
sister chromatids separate
Telophase II & Cytokinesis
nuclear envelope reforms and the cytoplasm divides
What’s the Principle of Independent Assortment?
the random separation of homologous chromosomes during meiosis I that results in a variety of combinations or maternal and paternal chromosomes
What does crossing over produce?
genetic diversity btwn homologous chromosomes, new combos of alleles on the same chromosome, and combinations that did not exist in each parent
nondisjunction
if both homologs or both sister chromatids move to the same pole of the parent cell (fail to separate)
Trisomy 21
47, +21 (Down Syndrome)
Turner Syndrome
45, X
Klinefelter syndrome
47, XXY
Jacobs Syndrome
47, XYY
