Cell Division

Week 1: Wednesday, August 27th: Lab Worksheet 1A: Cell Division; Week 3: Monday, September 8th

Chromosomes are replicated for cell division during _______

mitosis

Chromosome number is reduced in half to produce haploid gametes for reproduction during _______

meiosis

These chromosomes coil from loose strands of chromatin (DNA wrapped around histones), which involves the coordination between histone proteins, cohesin, and condensin. They also help hold sister chromatids together

eykaryotic chromosomes

_______ move chromosmes into position for cell division

spindle fibers

prokaryotes often have one _______ chromosome

circular

True or false: There aren’t any prokaryotes that have linear chromosomes

false. Borrelia burgdorferi have linear chromosomes

_______ hold prokaryote chromosomes in place

nucleoid associated proteins (NAPs)

true or false: fibers attach to centromere on either side of sister chromatids (+spindles bind to -kinetochore)

true

spindle fibers binding to chromosomes promotes _______, during which chromosomes are pushed to the cell center from either side to create _______. This ensures that chromosomes are in the right position for cell division

bi-orientation, tensional equlibrium (bipolarity)

_______ is when sister chromatids separate when they’re lined up properly, which is a good thing

disjunction

_______ is when fibers fail to attach to chromosomes, so the cell divides with an unequal chromsome number, which is a bad thing

nondisjunction

true or false: eukaryotic chromosome number differs among species, and correlates with the complexity of the organism

false. eukaryotic chromosome number differs among species, and doesn’t correlate with the complexity of the organism

true or false: eukaryotes that undergo sexual reproduction have an even number of chromosomes

true

true or false: if sex is determined by chromosome number rather than the X-Y system in humans, this number can be odd

true

among bees, the copies of chromosomes matter because haploid states produce females, but fertilization results in diploid zygotes, which produces males. this is referred to as a _______

haplodiploidy system

True or False: Mitosis occurs in eukaryotes and prokaryotes because they both have spindle fibers.

false. mitosis is unique to eukaryotes because prokaryotes lack spindle fibers.

in mitosis, fibers attach to _______ sides of the chromosome to separate _______

both, sister chromatids

in meiosis 1, fibers attach to _______ of each chromosome to separate _______

one side, homologs

in meiosis 2, fibers attach to _______ to separate homologs into _______

both sides, sister chromatids

when the cell is preparing for DNA synthesis, replicating DNA, and growing, it is in

Interphase (G1, S, G2)

this phase of interphase involves cell growth, organelle production, and division enzyme production

G1 phase

This phase of interphase involves the duplication of the centromere, then DNA (p and q arms), them centrosomes

S phase

this phase of interphase involves more growth, more energy generated, more enzymes made, and cohesion digestion

G2 phase

this checkpoint of interphase ensures the cell is healthy and ready for division; cyclin proteins adn kinases must be readily available to mediate cell passage through check points

G1 checkpoint

this checkpoint of interphase ensures DNA replication forks are stable

S checkpoint

this checkpoint of interphase ensures DNA was replicated proerly during S phase

G2 checkpoint

this checkpoint of interphase ensures spindles are attached for disjunction

M checkpoint

true or false: ignoring checkpoints can lead to unregualted cell growth

true

when chromosomes are dividing, the cell is in _______

M phase

true or false: after mitosis, cells have to stay active

false. after mitosis, cells can move to G0 (resting state)

what stage of cell division is this?

interphase

during this phase of mitosis:

1. chromosomes condense and are in random fashion

2. the nuclear membrane and nucleolus condense

3. spindle fibers begin to form from microtubule-organizing centers (MTOC)

4. replicated chromosomes move to opposite sides

prophase

what stage of cell division is this?

prophase

during this phase of mitosis:

1. microtubule-organizing center (MTOC) of the centrosome creates spindle apparatus

2. spindle fibers attach to both kinetochores of sister chromatids

3. the nuclear membrane and nucleolus completely dissolves

prometaphase

what stage of cell division is this?

prometaphase

during this phase of cell division:

1. spindle fibers lengthen and align the sister chromatids in the middle of the cell with the involvement of bi-orientation

2. the cell clears M checkpoint once balance is detected, and the last of cohesin is digested

metaphase

what stage of cell division is this?

metaphase

during this phase of cell division:

1. 46 pairs of sister chromatids separate

2. microtubules disassemble and pull a set of now 46 daughter chromosomes back to opposite sides

anaphase

what stage of cell division is this?

anaphase 

during this phase of mitosis:

1. daughter chromosomes relax into chromatin

2. two nuclei form around each set of daughter chromosomes in a single cell

3. ER rebuilds the nuclear membrane around them, which leads to cell division

telophase

what stage of cell division is this?

telophase

during this phase of cell division:

1. the cell divides in half to form two new cells by a cleavage furrow for animals, or a cell plate for plants

2. two daughter diploid cells are created

cytokinesis

what stage of cell division is this?

cytokinesis 

true or false: meiosis interphase is different from mitosis interphase

false. meiosis interphase is the same steps as mitosis interphase

_______ involves tetrad synapse, cross-over in holliday junctions, and chromosome separation from diploid to haploid

meiosis 1

during this phase of cell division:

1. the phase is prolonged

2. pairs of homologous chromosomes line up side-by-side (synapsis) to form a tetrad

3. SPO11 makes double-stranded DNA breaks for allelic changes between homologs

4. synapsis crossing-over occurs

5. spindle fibers attach again

prophase 1

what stage of cell division is this? 

prophase 1

_______ holds tetrads together during prohase 1. they’re then held by chiasmata

synaptonemal complex (SC)

true or false: during meiosis, cells go through a prometaphase stage

false. during meiosis, cell don’t go through a prometaphase stage because spindle fibers are already attached during prophase

during this phase of cell division:

1. spindle fibers bind to the outer sides of the recombined tetrads

2. recombined tetrads are pushed to cell center and held together by spindle fibers (chiasmata prevents them from binding to the inner sides of tetrads like in mitosis)

metaphase 1

what stage of cell division is this? 

metaphase 1

during this phase of cell division:

1. spindle fibers dissemble

2. recombined homologous chromosomes separate into only paternal or only maternal haploid sister chromatid sets to opposite poles (sister chromatids aren’t pulled apart)

anaphase 1

what stage of cell division is this? 

anaphase 1

during this phase of cell division:

1. two nuclei form around each set of sister chromatids, which are enclosed by separate nuclear membranes

2. two recombined haploid cells are created

telophase 1

what stage of cell division is this? 

telophase 1

chromosome reduction occurs _______ Meiosis 1, (before interkinesis) where homologous chromosomes are separated

after

haploid sister chromatids are seaprated in _______, which produces haploid gametes

meiosis 2

during this stage of cell division:

1. there’s no S phase

2. G1 and G2 phases are reduced

3. two haploid cells are preparing to divide

interkinesis

during this phase of cell division,

1. haploid cells made of recombined sister chromatids prepare to divide again

2. they condense and alighn at right angles at the plane of division of meiosis 1

3. spindle fibers attach

prophase 2

what stage of cell division is this? 

prophase 2

during this stage of cell division:

1. recombined haploid sister chromatids line up at the cell center

2. spindle fibers attach to the kinetochores on both sides of the centromeres

metaphase 2

what stage of cell division is this? 

metaphase 2

during this phase of cell division:

1. sister chromatids separate

2. cohesin is digested

3. spindle fibers break down

4. chromatids separate into haploid daughter chromosomes and are pulled apart

anaphase 2

what stage of cell division is this? 

anaphase 2

during this phase of cell division:

1. two nuclei form around each set of haploid daughter chromosomes

2. the second set of cell division occurs

telophase 2

what stage of cell division is this? 

telophase 2

during this phase of cell division:

1. four recombined haploid gametes in human males are produced

2. and one big oocyte and three degenerated cells in females are produced

cytokinesis

cohesin and _______ prevent sister chromatids from separating during mitosis and meiosis

shugoshin

_______ digests cohesion to allow anaphase to begin

separase

cohesion is only left between the centromeres during _______; and lasting until _______

metaphase, metaphase 2

meiosis produces gametes that then undergo _______ after zygote formation during fertilization.

mitosis

during zygote formation, sperm binds to ZP3 receptors on a hardened membrane surrounding the oocyte that prevents additional fertilization, which is referred to as the _______

zona pellucida

during zygote formation, sperm binding to an oocyte causes an _______ reaction that releases digestive enzymes so sperm can eat through the oocyte’s plasma membrane

acrosomal

true or false: during zygote formation, the mother cell provides organelles and cytoplasm

true

during zygote formation, the zygote goes through duplicative mitotic divisions (cleavage) to form 2, then 4, then 8, then 16 cells—all of which are a _______ and undifferentiated.

morula

during zygote formation, the morula develops into a 32-cell stage that forms a _______ and creates a fluid-filled hollow center.

blastula

during zygote formation, there’s an increase in size to accomodate the increasing number of cells

false. there’s no increase in size, so cells shrink to accommodate the increasing number

blastulation involves cell migration, and _______, which leads to three primal cell layers: endoderm, mesoderm, and ectoderm

gastrulation

during zygote formation, the three primal cell layers, which differentiate and end in _______, when the neural plate transforms into the neural tube

neurulation

sexual differentiation begins around _______, wheras fetus formation begins by the end of _______

week 6, week 8

one chromosome and a copy of the same chromosome, which is created during Mitosis S-Phase, is defined as a pair of ____

sister chromatids

chromosomes that are identical to sister chromatids, but separated and independent during mitosis anaphase, are defined as _______

daughter chromosomes

4 chromatids that consist of one chromosome from each parent and their copies are defined as _______ and are present during meiosis prophase 1

tetrads

chromatin (DNA + histones) is coiled by _______

condesin