Section 5: Cell Division Flashcards
What is the term for nuclear division?
What follows nuclear division?
Karyokinesis
Cytokinesis
In diploid cells, there are 2 copies of every______, forming a pair, which is called a ______
Chromosome
homologous chromosome
Humans have ____ chromosomes, ____ homologous pairs, and a total of _____ chromatids
46 chromosomes
23 pairs
92 chromatids (depending upon stage of division 1)
These are also known as centrosomes. A pair of them lay outside the nucleus
Microtubule organizing centers
In animal cells, each MTOC contains a pair of
Centrioles
In this phase of MITOSIS, the nucleus dissassembles
Prophase
During prophase of mitosis, the nucleus disassembles and and the ______ appear
What condenses into chromosomes?
What breaks down?
What two things are formed?
Nucleolus
Chromatin
The nuclear envelope
Mitotic Spindle and microtubules
What are the microtubules of the mitotic spindle that is formed during prophase of mitosis made of?
Where do they begin to connect with?
Tubulin
Kinetochores
The protein structure on chromatids where the spindle fibers attach during cell division to pull sister chromatids apart.
Kinetochore
During this phase of mitosis, chromosomes line up single file at center
Metaphase
During the metaphase of mitosis, each chromatid is complete with a ______ and a _____
Once separated, it is a
To keep track of total, count the number of….
Centromere and kinetochore
Chromosome
Centromeres
During mitosis, once the chromatid is separated, that is the end of _______
The chromosome number does what during the next phase?
metaphase
Doubles
Karyotyping occurs during which phase of mitosis?
Metaphase
During this phase of mitosis, microtubules shorten, and each chromosome is pulled apart into two ________
Anaphase
Chromatids
Remember that when two DNA molecules are joined together, each molecule is called a chromatid and the two of the molecules are called a duplicated chromosome. When a DNA molecule(and proteins) is not attached to another one then that single molecule of DNA is not a chromatid but an unduplicated chromosome.
!! Important distinction
During anaphase of mitosis, what happens to the chromosome number?
It doubles, because duplicated chromosomes are pulled apart to opposite poles
What is it called when the chromosomes are pulled to apart to opposite poles of the cell during mitosis?
Disjunction
During mitosis, at the end of _______, each pole has a complete set of chromosomes, same as original cell before replication
Anaphase
During mitosis, this is the phase of nuclear division
What develops?
The chromosomes uncoil and become…
What reappear?
Telophase
Nuclear envelope
Chromatin
Nucleoli
This is a particular region of the nucleus containing chromosomal regions of cells
Nucleolus
What begins during the later stages of mitosis, aka at the end of anaphase?
Cytokinesis, the division of cytoplasm to form 2 cells
During cytokinesis, these microfilaments shorten, pulling the plasma membrane to the center (animals)
What is this process called?
Actin and myosin
Cleavage furrow
During cytokinesis in plants, vesicles from Golgi bodies migrate and fuse to form…
Out growth occurs and merging with the _____ separating the two new cells.
Do cells actually separate?
What cements adjacent cells together, then?
Cell plate
Plasma membrane
No, they are cemented together
Middle Lamella
This phase begins after mitosis and cytokinesis are complete, and consists of G1, S, and G2 phases
Interphase
What are the phases of the cell cycle in order?
M, G1, S, G2,
During the ___ phase of interphase, the second molecule of DNA is replicated from the first, forming sister chromatids
S phase
Is more time spent during interphase or mitosis?
Interphase
During interphase, does growth only occur during G’s?
No, it occurs in all 3 interphases
During which interphase are the materials for the next mitotic division prepared?
G2
There are checkpoints at each interphase to make sure things are going as planned
Near the end of ____, cell growth is assessed and favorable conditions are checked. If this fails, the cell enters
Near the end of ____, checks for sufficient mitosis promoting factor levels required to proceed
There is an M checkpoint during mitosis that triggers start of…
G1
G0
G2
G1
This part of MEIOSIS is reduction division
Meiosis 1
In this PHASE of meiosis, homologous chromosomes pair at the plate and migrate to opposite poles
Is there separation of sister chromatids?
What develops?
Microtubules attach to ____
Crossing over means genetic ____
This could change the ___ sequence
Prophase I
No.
Spindle
Kinetochores
recombination
Nucleotide sequnce
This is the term for when homologous chromosomes pair up during prophase I of meiosis
The pairs are referred to as ___ or ____
Synapsis
Tetrads or bivalents
During prophase I of meiosis, this is the region where crossing over occurs of non-sister chromatids
Chiasmata
During prophase I of meiosis, this is the protein structure that temporarily forms between homologous chromosomes: gives rise tothe tetrad w/ chiasmata and crossing over
Synaptonemal complex
How many phases does prophase I of meiosis have?
What are they?
5
Leptotene Zygotene Pachytene Diplotene Diakinesis
In this step of prophase I, chromosomes start condensing
Leptotene
In this step of prophase I, synapsis beings; the synaptonemal complex is forming
Zygotene
In this step of prophase I, synapsis is complete, and crossing over occurs
Pachytene
In this step of prophase I, the synaptonemal complex disappears and the chiasma is still present
Diplotene
In this step of prophase I, the nuclear envelope fragments, and chromosomes complete condensing, tetrads are ready for metaphase
Diakinesis
During this phase of MEIOSIS, homologous pairs are spread across the metaphase plate
_____ are attached to kinetochores of one member of each homologous pair. They one member then attach to the 2nd member of the pair
Metaphase I
Microtubules
During this phase of meosis, homologues within tetrads uncouple and are pulled to opposite sides
The term for pulling apart is…
Anaphase I
disjunction
During this phase of meiosis, the nuclear membrane develops. Each pole forms a new nucleus
What proportion of chromosomes do the new nucleus’ have from the beginning?
Telophase I
Half the chromosomes
This is the chromosome reduction phase of meiosis to haploid
Telophase I
Depending upon the species, what may occur after telophase I of meiosis?
Interphase
In this part of meiosis, chromosomes spread across metaphase plate and sister chromatids separate and migrate to opposite poles. It is
similar to mitosis.
Meiosis II
In this phase of meiosis, the nuclear envelope disappears and the spindle develops, etc,
Is there chiasmata or crossing over?
Prophase II
No.
During this phase of meiosis, the chromosomes align on a plate like in mitosis but now with half the number of chromosomes (no extra copy)
Metaphase II
During this phase of meiosis, each chromosome is pulled into 2 separate chromatids and migrate to opposite poles of the cell
Anaphase II
During this phase of meiosis, the nuclear envelope reappears and cytokinesis occurs
How many cells are created?
Are they diploid or haploid?
Telophase II
4
haploid (each chromosome=1 chromatid)
What type of cell division occurs in somatic cells?
What type of cell division occurs in gametes?
Mitosis
Meiosis (egg, sperm, pollen)
This is the fusion of two haploid gametes
It forms a…
This is meoisis, right?
Fertilization/syngamy
diploid zygote
In plants what produces spores?
Are these diploid or haploid?
Spores undergo MEIOSIS/MITOSIS to become multicellular
Once multicellular, they are called
Sporangia
Haploid
Mitosis
Gametophytes
Gametophytes are diploid or haploid?
The gametes fuse and produce a
This grows to become a
Haploid, since spores are already haploid
Diploid Zygote (2n)
Sporophyte
Cells in the sporophyte (sporangia) undergoes MITOSIS/MEIOSIS to produce haploid spores which germinate and repeat the life cycle
Meiosis (check out diagram in feralis notes)
This is a term primarily used to describe the life cycle of plants (taken here to mean the Archaeplastida). A multicellular gametophyte, which is haploid with n chromosomes, alternates with a multicellular sporophyte, which is diploid with 2n chromosomes, made up of n pairs. A mature sporophyte produces spores by meiosis, a process which reduces the number of chromosomes to half, from 2n to n.
Alternation of generations (alternation of diploid and haploid stages in plants)
Genetic variation (genetic recombination during meiosis and sexual reproduction) results from 3 events. What are they?
Crossing over during Prophase I
Independent assortment of homologues during metaphase (which chromosome goes into which cell)
Random joining of gamete aka germ cells (which sperm fertilizes which egg)
In the regulation of the cell cycle, the volume gets much larger when cells grow. When this value is small, exchange is hard, leading to cell death or cell division to increase surface area. When the value is large, exchange becomes much easier
What is the volume equation?
What is the SA equation?
Surface to volume ratio
4/3πr^3
4πr^2
In the regulation of the cell cycle, the genome size remains constant throughout life. As the cell grows, the volume increases.
The value will be small and thus exceed the ability of its genome to produce sufficient amounts of regulator of activites
Genome to volume ratio
What do some large cells have to deal with small genome to volume (G/V) ratios?
They are multinucleated (paramecium, human skeletal muscle)
In the checkpoints of the cell cycle, this is the restriction point, the most important one. At the end of the phase, if the cell is not ready to divide it may arrest here and never proceed or wait until it is ready
What phase will it go to if it is not ready?
what cells rarely proceed to division after maturing, and therefore go to G0?
G1 checkpoint
G0 phase
Nerve and muscle cells
In the checkpoint of the cell cycle, this one evaluates the accuracy of DNA replication and signals whether to begin mitosis
G2 checkpoint
In the checkpoints of the cell cycle, this occurs during metaphase and ensure microtubules are properly atteached to kinetochores
M checkpoint
These are enzymes that activate proteins that regulate cell cycle by phosphorylation
What are they activated by?
Cyclin-dependent kinases (CDKs)
Cyclin (duh)
The plasma membrane has receptors for _______ that stimulate cell for division (such as damaged cell)
growth factors
This occurs when cells stop dividing when surrounding cells density reaches maximum.
Density Dependent Inhibition
Most cells only divide when attached to an external surface such as neighboring cells or side of culture dish. This regulation is called
Anchorage dependence
What type of cells defy all 5 of the cell specific conditions mentioned before (Checkpoint, CDKs, Growth factors, Density dependent inhibition, anchorage dependence)
Cancer cells
How many chromosomes are there in the anaphase of mitosis if a cell has 46 chromosomes at the beginning?
What can be counted to give this value?
92
(46 chromosomes made of 2 sister chromatids are pulled apart to give 92 chromosomes)
Centromere
At anaphase I, how many chromosomes are there if a cell has 46 chromosomes at the beginning?
46 (23 chromosomes that are pulled to each pole, no separation of sister chromatids at anaphase I)
Do plants have centrioles?
Why or why not?
No
The cell plate forms
Which has no genetic variation, mitosis or meiosis?
mitosis
