Flashcards in Chapter 3: Cell Division Deck (48):
What's the purpose of mitosis?
mitosis makes two (2) identical daughter cells with the same number of chromosomes.
The daughter cells of mitosis are ___.
diploid (2n), just like the parent cell.
What's the purpose of meiosis?
meiosis makes gametes (sex cells) with half the number of chromosomes as the parent.
The daughter cells of meiosis are ___.
haploid, they have half (1/2) less chromosomes than the parent.
What is a chromosome?
a chromosome is a highly coiled and condensed strand of DNA
What's each chromosome made up of?
each chromosome is made up of TWO (2) sister chromatids.
What's the centromere?
the centromere holds the two sister chromatids together.
What's the cell cycle?
the cell cycle is a sequence of growth and division.
What cells divide constantly throughout your life?
skin cells and cells in the digestive tract divide constantly throughout your life.
What's the G0 phase in the cell cycle?
the phase when cells DO NOT divide.
What cells may enter the G0 phase?
specialized cells like NERVE and MUSCLE cells enter the G0 phase
What're stem cells?
1. can divide indefinitely
2. can differentiate (or become) any cell type
- for example a stem cell can become a brain cell or a liver cell once it matures.
cyclins are PROTEINS
What do cyclins do?
cyclins REGULATE the cell cycle!
What do protein internal regulators do in the cell cycle?
they make sure the cell doesn't divide until certain conditions are met.
What do external regulators do in the cell cycle?
they can speed up, slow down, or stop the cell cycle
What's an example of an external regulator?
What're the stages of the cell cycle?
1. Growth1 (G1)
2. Synthesis (S)
3. Growth2 (G2)
How many checkpoints are in the cell cycle?
there are THREE (3) checkpoints in the cell cycle!
What happens during the G1 phase?
during the G1 phase
1. the cell grows
2. the cell prepares to replicate its DNA
When does the cell enter the G1 phase?
when it finishes dividing (the mitosis and cytokinesis phases).
Where are the three (3) checkpoints in the cell cycle?
checkpoints in the cell cycle:
1. G1 checkpoint: after G1
2. S checkpoint: After S
3. G2 checkpoint: after G2
What does the G1 checkpoint do?
the G1 checkpoint
1. uses growth factors to make the cell go to the next phase (Synthesis) if the cell is healthy, has enough resources to do so, and the DNA is not damaged
2. makes the cell die or go into the G0 non dividing phase if it doesn't meet the conditions above.
What does the S checkpoint do?
The S checkpoint uses growth signals to stimulate the cell to go to the G2 phase if there are no errors in making the extra copy of DNA
When does the G2 checkpoint allow the cell to enter mitosis?
the G2 checkpoint allows the cell to enter mitosis if:
1. the chromosomes are fully replicated
2. and the chromosomes are not damaged
What happens if there are errors in the cell cycle?
it may cause CANCER.
What phases does interphase include?
1. Growth 1 (G1)
2. Synthesis (S)
3. Growth 2 (G2)
What percent of its life does the cell spend in interphase?
the cell spends NINETY percent (90%) of its life in interphase
What happens during interphase? (3)
1. chromosomes replicate during the synthesis phase
2. one or more (1+) nucleoli become visible
3. the nuclear membrane remains intact.
What're the stages of mitosis? (4)
stages of mitosis:
What happens during mitosis?
during mitosis, the NUCLEUS divides
What happens during prophase in mitosis? (5)
1. chromosomes condense and become visible
2. the nucleoli dissapear
3. spindle fibers form in the cytoplasm
4. centrioles move to the poles
5. nuclear membrane breaks down.
What happens during metaphase in mitosis? (3)
1. chromosomes line up in the MIDDLE of the cell on the metaphase plate.
2. centrosomes are at the opposite poles of the cell
3. spindle fibers connect the centromeres of the sister chromatids to the centrosomes.
During metaphase, where do the chromosomes line up?
During metaphase, the chromosomes line up in the middle of the cell on the METAPHASE PLATE.
What happens during anaphase in mitosis?
1. the spindle fibers pull the sister chromatids apart.
What happens during telophase in mitosis? (3)
1. the separated chromosomes finish moving to the different ends of the cell
2. the nuclear membrane re-forms
3. the chromosomes unravel
What happens during cytokinesis?
during cytokinesis, the cytoplasm DIVIDES.
What happens during cytokinesis in animal cells?
during cytokinesis in animal cells, a CLEAVAGE FURROW forms down the middle of the cell.
What happens during cytokinesis in plant cells?
during cytokinesis in plant cells,
1. a CELL PLATE forms down the middle of the cell
2. daughter cells DO NOT separate
3. a sticky middle lamella layer joins adjacent cells together
Do the daughter cells separate in plant cells during cytokinesis?
NO! the middle lamella layer joins the adjacent daughter cells TOGETHER.
What're the stages of mitosis?
stages of mitosis:
1. meiosis 1
2. meiosis 2
What happens during meiosis 1, the first stage of meiosis?
in meiosis 1:
1. synapsis occurs
2. crossing over occurs
3. pairs of chromosomes separate
What's synapsis in meiosis 1?
synapsis is when chromosomes pair up with their homologue to prepare for crossing over
What's crossing over in meiosis 1?
crossing over is when homologous chromosomes exchange DNA
nondisjunction is when homologous chromosomes FAIL TO SEPARATE!
What happens during meiosis 2, the first stage of meiosis?
in meiosis 2, the SISTER CHROMATIDS separate!
In which stage in the life of a cell is the nucleolus visible?
the nucleolus is visible in the E. INTERPHASE phase!