7: mitosis/meiosis/cell cycle Flashcards
Bacterial DNA replication
Single, uncoiled ring of DNA replicates away from the origin in both directions until all of the DNA is copied. DNA is also stored in plasmids.
Centromere (def. & number)
Platform in the middle of a (duplicated) chromosome where sister chromatids are most tightly connected and where the kinetochores are built; 1 centromere per chromatid, so 2 per duplicated chromosome
Kinetochore (def. & number)
Protein complex built on the centromere where microtubules connect during anaphase; 1 kinetochore per chromatid, so 2 per duplicated chromosome
Chromatin
Stack of nucleosomes (which are DNA + histones)
Nucleosome
DNA coiled around a histone
Chromatid
Made of chromatin
Cell specialization due to
The way DNA strands are wrapped around histones (which sections of genes are accessible and therefore code for things, and which sections aren’t)
Stages of interphase
1) G1 - Cell grows more organelles (except mitochondria/chloroplasts) and cytoplasm, as well as cell membrane
2) S - DNA replicates to prepare for division’
3) G2 - Chloroplast and mitochondria replicate, DNA condenses into chromosomes, and microtubules are synthesized
3 checkpoints
Mitotic/metaphase/spindle checkpoint
G1/S checkpoint
G2/M checkpoint
Mitotic/metaphase/spindle checkpoint
Assesses whether microtubules are properly attached to kinetochores of sister chromatids; allows cell to go from metaphase to anaphase if passed. If it is not passed, the cell will delay anaphase until all kinetochores are attached to microtubules.
G1/S checkpoint
Assesses the V/SA ratio, nutritional state, and local cell density (contact inhibition) - if they are sufficient, the DNA will replicate and the cell will prepare to divide. If something is wrong, the cell will enter G0 and may stay there permanently or may enter G1 again when conditions improve.
G2/M checkpoint
Assesses whether the DNA (from S) has been replicated correctly before the cell undergoes mitosis. If the DNA is damaged, the p53 (a tumor suppressor) gene can repair the DNA or cause apoptosis. If the DNA is correct, the cell will enter mitosis.
Centrioles
2 organelles that are found in the centrosome
Centrosomes
Organelles that organize and produce microtubules, which attach to chromosomes/chromatids (depending on meiosis/mitosis). They also migrate to opposite poles of the cells to lengthen it.
Mitotic spindle
Made of microtubules and proteins (taken from the disassembling of the cytoskeleton), specifically tubulin subunits, which allow the microtubules to shorten / lengthen