week 2 (cell division) Flashcards
question: what is the diff. between somatic cells and gametes?
- somatic= diploid, divide by mitosis
- gametes = haploid, divide by meiosis
question: what type of cells are produced by mitosis vs meiosis?
- mitosis prod. diploids
- meiosis prod. haploids
name: stages of mitotic cycle in order
2 phases
INTERPHASE
G1
S
G2
G0
M PHASE
mitosis
explain: what happens in each stage of interphase
G1
- prepare for DNA replication
S
- DNA replication occurs
G2
- prepare for cell division
G0
- resting phase, not dividing
explain: what happens in each stage of m phase
G2 (interphase)
- preparing for cell division
- chromosomes already duplicated
prophase
- duplicated DNA separates
- still chromosomes
prometaphase
- nuclear envelope fragments
- microtubules attach to centromeres
metaphase
- chromosomes align at metaphase plate
anaphase
- sister chromatids separate
telophase
- new nuclear membranes form
cytokinesis
- daughter cells separate
question: what are the amounts of chromosomes and chromatids at G1, S, and mitosis?
**all in nanograms
G1
- chromosomes = 46
- chromatids = 46
S
- chromosomes = 46
- chromatids = 92
mitosis
- chromosomes = 46
- chromatids = 46
name + explain: checkpoints in cell cycle (4)
1. G2 checkpoint
- checking cell size and correct chromo. replication
2. metaphase checkpoint
- checking all chromo. attached to mitotic spindle
3. G1 checkpoint
- checking cell size and sufficient nutrients
4. S checkpoint
- checking if DNA replication complete and no mismatches or errors
name: full order of cell cycle (w/ checkpoints)
1,.G1
2. G1 checkpoint
3. S
4. S checkpoint
5. G2
6. G2 checkpoint
7. prophase
8. metaphase
9. metaphase checkpoint
10. anaphase
11. telophase and cytokinesis
question: what cell do you start with for meiosis?
- diploid
- has unreplicated chromosomes
explain: what happens in each stage of meiosis
INTERPHASE
- chromatids duplicated but homologous chromo. stay separated
METAPHASE I (meiosis I)
- homologous chromosomes separated into cells (2)
METAPHASE II (meiosis II)
- each duplicated homologous chromo. (sister chromatid) separated into cells (4)
⤷ gametes
explain: what happens in the stages of meiosis I
- homologous chromosomes pair
- crossing over occurs (recomb.)
- duplicated homologous chromo. separated into 2 daughter cells
PROPHASE I
- homologous chromo. pair and recombine into tetrads
METAPHASE I
- pairs align
ANAPHASE I
- chromo. separate
- sister chromatids stay attached
TELOPHASE I
- nuclear membranes form for 2 daughter cells
- cells separate in cytokinesis
explain: what happens in the stages of meiosis I
- sister chromatids separate into separate daughter cells
- results in 4 haploid cells
PROPHASE II
- nuclear envelope breaks down
METAPHASE II
- pairs align at plate
ANAPHASE II
- chromatids split at centromere and get pulled to poles
TELOPHASE II
- nuclear membranes form for 4 daughter cells
- cells separate in cytokinesis
question: when does recombination happens?
- in prophase I of meiosis I
- before metaphase
question: what are the amounts of chromosomes and chromatids at G1, S, meiosis I, and meiosis II?
**all in nanograms
G1
- chromosomes = 46
- chromatids = 46
S
- chromosomes = 46
- chromatids = 92
meiosis I
- chromosomes = 23
- chromatids = 46
meiosis II
- chromosomes = 23
- chromatids = 23
explain: sex determination in drosophila vs humans
- humans: Y determines male
- drosophila: ratio of X chromo. to autosomes determines sex
⤷ females have more X chromo.
question: how does sex determination in flies work?
- sisterless prot. = expressed by X chromo.
- deadpan prot. = expressed by autosomes
- 2 sisterless dimerize = female
- 1 sisterless, 1 deadpan dimerize= male
- 2 X chromo. = more sisterless = higher chance of 2 sisterless dimerizing
define + explain: hypertrichosis
- X linked dominant condition
- increase number of hair on body
explain: X inactivation in female mammals
- cells inactivates either maternal X chromo. or paternal X chromo. randomly
- happens early in embyronic dev.
- means all cells in a females body is a mosaic of maternal X and paternal X expressions
name: an example of X inactivation
- calico cats
- X carries genes for cat colour
⤷ one allele for orange, one for black - inactivating leads to patches of colours
- lines of Blaschko (in humans)
