CH 12 Flashcards
Mitosis
- the division of the nucleus followed by the division of the cytoplasm (cytokinesis)
produces two identical daughter cells
Meiosis
eukaryotic cell division that can produce sperm
and eggs
- located in our gonads (ovaries or testes) producing gametes
Genome
a cell’s genetic information, packaged as DNA
Somatic cells
all body cells except sperm and egg have 46 chromosomes, made up of two sets of 23
Gametes
human reproductive cells (sperm/eggs) have one set of 23 chromosomes
what does each chromosome look like when the cell is not dividing?
a long, thin chromatin fiber
what happens to chromatin before cell division but after DNA replication?
chromatin condenses, coils, and folds to make a smaller package
Sister chromatids
the identical copies formed by the DNA replication of a chromosomes joined by a centromere
how many centromeres are there?
2
how many chromosomes did we get from each parent?
23 - one set in egg, and one set in sperm, total of 46
how many daughter cells produced by meiosis? are they identical?
4 nonidentical daughter cells, each with half the chromosomes of the parent
what includes in mitotic phase of the cell cycle? what phase does mitotic alternate with?
mitosis and cytokinesis, alternates with
the much longer interphase.
How many subphases does the interphase have and what are they?
3 subphases
- the G1 phase (“first gap”)
- the S phase (“synthesis”)
- the G2phase (“second gap”).
Why do human cell might divide once every 24hours?
the M phase would last less than 1 hour
the S phase might take 10–12 hours, or half the cycle.
○ The rest of the time would be divided between the G1 and G2 phases.
○ The G1 phase varies most in length from cell to cell
Mitosis is usually divided into # subphases? and what are they?
5 subphases: prophase, prometaphase,
metaphase, anaphase, and telophase
What process completes mitosis?
Cytokinesis
What happens in late interphase? (4)
the chromosomes have been duplicated but are not condensed.
○ A nuclear membrane bounds the nucleus, which contains one or more nucleoli.
○ The centrosome has replicated to form two centrosomes.
○ In animal cells, each centrosome features two centrioles
What happens in prophase? (5)
the chromosomes are tightly coiled, with sister chromatids joined together.
○ The nucleoli disappear.
○ The mitotic spindle begins to form. It is composed of centrosomes and the microtubules that
extend from them.
○ The radial arrays of shorter microtubules that extend from the centrosomes are called asters.
○ The centrosomes move away from each other, apparently propelled by lengthening
microtubules
What happens in prometaphase?
the nuclear envelope fragments, and microtubules from the spindle interact
with the condensed chromosomes.
○ Each of the two chromatids of a chromosome has a kinetochore, a specialized protein
structure located at the centromere.
○ Kinetochore microtubules from each pole attach to one of two kinetochores.
What happens in metaphase?
The spindle fibers push the sister chromatids until they are all arranged at the metaphase plate,
an imaginary plane equidistant from the poles
What happens in anaphase?
the centromeres divide, separating the sister chromatids.
○ Each chromatid is pulled toward the pole to which it is attached by spindle fibers.
○ By the end, the two poles have equivalent collections of chromosomes
What happens in telophase?
daughter nuclei begin to form at the two poles
○ Nuclear envelopes arise from the fragments of the parent cell’s nuclear envelope and other
portions of the endomembrane system.
○ The chromosomes become less tightly coiled
What happens in cytokinesis?
division of the cytoplasm, is usually well under way by late telophase
○ In animal cells, cytokinesis involves the formation of a cleavage furrow, which pinches the
cell in two.
○ In plant cells, vesicles derived from the Golgi apparatus produce a cell plate at the middle of
the cell
