Flashcards in Chapter 4 Deck (61)
In mitosis, which plane do the two daughter cells divide one?
they divide longitudinally
When a cell is not dividing, it is in ___stage
interphase stage, g1
2 daughter cells, both of whom receive identical diploid complements to the diploid complement of the cell.
What're the three substages of interphase?
G1, S, G2
What is happening at G1?
cell growth, organelle replication, replication of centrosome
Which checkpoint determines if the cell can leave the G1 stage? What're the conditions for the cell to proceed?
G1/S check point dictates whether or not the call can proceed to the S stage of interphase.
Conditions: large enough cell size must be obtained, sufficient time elapsed since last cell division.
What occurs in S stage?
DNA replication and chromosome duplication
Which checkpoint detemines if a cell can leave the S stage? What're the the conditions for the cell to undergo mitosis?
after the dna is replicated, the cell goes into G2 phase, which is just a post DNA synthesis stage, where it continues to prep for cell division. the cell will not undergo mitosis unless all repair and DNA synthesis is complete (won't leave the G2/M checkpoint
In proohase, chromatin starts to condense into threads of chromosomes with the help of ____protein complexes
how many centromere does each sister chromatid have?
each chromatid has one centromere that joins them together, therefore, in a sister chromatid pair, there are two centromeres.
What kind of protein holds the sister chromatids together until anaphase?
Summarize what happens in prophase.
the duplicated chromatin begin to condense with the help of condensin proteins. The sister chromatids then get held together by cohesin protein and are joined together at their centromeres. The nucleolus disappears and the nuclear membrane disintegrates.
What are the mitotic spindles made of? Where is polymerization of the spindle building blocks taking place?
mitotic spindles are made of tubulin proteins that make up microtubules. polymerization occurs at the centrosome: the organization centers at the poles.
How many centrosomes are at each pole?
there are two centrosomes at each pole in a duplicated cell. After mitosis, each daughter cell pocesses one pair of centrosomes.
At what stage of mitosis do the mitotic spindles begin to form?
what're the three main types of microtubule spindles in a cell?
1) ones that anchor the centrosome to the cell membrane
2) ones that arch between the chromosomes
3) one that attach to chromosomes
Usually, microtubules are unstable. At what point to the microtubule spindles get stabilized?
spindles that do not attach to anything disintegrate (arch between the chromosomes). Only when the spindles attach to a kinetochore do they become stabilized.
What events all occur in metaphase?
spindle apparatus gets assembled via the polymerization of microtubules, and the spindles attach to the kinetochores and line the chromosomes on the metaphase plate.
Is there a checkpoint in metaphase?
What conditions must be met in order for the cell to proceed past metaphase?
kinetochores must be perfectly aligned on the metaphase plate. when all the kinetochores are under tension, kinetochore-associated proteins get dephosphorylated, chemically signalling that metaphase is complete.
What happens in anaphase?
1) cohesins that were holding the two sister chromatids together disintegrate
2) Chromosomes separate and the sister chromosomes move to opposite poles as the microtubules that were connected to the kinetochore begin to depolymerize
3) cell elongates and the chromosomes are in 2 groups at opposite sides of the cell.
What happens in telophase?
the chromosomes begin to condense into the interphase form and the nuclear envelope reforms and the nucleolus reappears. The spindle apparatus disappear. Cytokinesis occurs in animal cells via cleavage furrow and cell plate formation occurs in plants.
Differences between mitosis and meiosis
1) synapsis and crossing over occurs in prophase I during meiosis
2) segregation of Homologous chromosomes in anaphase 1 instead of sister chromatids results in the daughter cells having half the original chromosomes
3) 2 nuclear divisions with no DNA replication between divisions
4) Meiosis produces 4 cells each genetically distince with half the amount of DNA of mitotic products.
What type of cells does meiosis take place in?
In the female of animals and plants, only one of the ___ cell products develops into a functional cell, the rest ___
one of the four cell products develop into a functional cell, the rest disintegrate.
In plants, products of meiosis form ____
The spores undergo mitotic division to produce a haploid _____ generation
gametophyte generation organism
the gametophyte generation produces ____ via mitosis or meiosis?
gametes via mitosis. it is already haploid
The haploid gametes fuse to create a ____