Bio Chapter 11 Launchpad
What are the five stages of mitosis? Draw the structure and position of the chromosomes at each stage.
(1) prophase (chromosomes condense, centrosomes radiate spindle microtubules and migrate to opposite poles (2) prometaphase (microtubules of the mitotic spindle attach to chromosomes) (3) metaphase (chromosomes align in center of cell) (4) anaphase (sister chromatids separate and move to opposite poles) (5) telophase (nuclear envelope re-forms and chromosomes decondense)
Meiosis number of rounds of DNA synthesis
1
Mitosis number of cell divisions
1
Mitosis number of rounds of DNA synthesis
1
Meiosis number of cell divisions
2
Mitosis number of daughter cells
2
Meiosis number of daughter cells
4
At the start of mitosis, how many sister chromatids are present in a human cell?
46
centrosome
A compact structure that is the microtubule organizing center for animal cells.
Why don't plant cells use a contractile ring to divide their daughter cells?
A contractile ring can't "pinch" a cell wall.
chiasma
A crosslike structure within a bivalent constituting a physical manifestation of crossing over.
meiotic cell division
A form of cell division that includes only one round of DNA replication but two rounds of nuclear division; meiotic cell division makes sexual reproduction possible.
bivalent
A four-stranded chromosomal structure formed in prophase I of meiosis composed of a pair of homologous chromosomes, each consisting of two chromatids, paired side by side and held together by one or more chiasmata.
What do you predict would be the consequence of a mutation in FtsZ that disrupts the function of the protein it encodes?
A mutation that disrupts the function of the FtsZ protein will block cell division (specifically, cytokinesis).
karyotype
A standard arrangement of chromosomes, showing the number and shapes of the chromosomes representative of a species.
mitotic spindle
A structure in the cytosol made up predominantly of microtubules that pull the chromosomes into separate daughter cells.
Mitosis Organisms
All eukaryotes
Muscle cells in the mammalian heart are multinucleate, meaning that multiple nuclei are present in the cytoplasm of individual large cells. Predict what is different about the cell cycle in a muscle cell.
Cytokinesis does not occur.
Which statement is true regarding binary fission?
DNA replication of the circular bacterial chromosome during binary fission is a bidirectional process, starting at one point but progressing in opposite directions.
haploid
Describes a cell with one complete set of chromosomes.
diploid
Describes a cell with two complete sets of chromosomes.
homologous
Describes characters that are similar in different species because of descent from a common ancestor.
Meiosis _____ is similar to mitosis in that _____ separate.
II; sister chromatids separate
contractile ring
In animal cells, a ring of actin filaments that forms at the equator of the cell perpendicular to the axis of what was the spindle at the beginning of cytokinesis.
Meiosis II pairing of homologous chromosomes
No
Would genetic recombination result if crossing over occurred between sister chromatids?
No, because sister chromatids are genetically identical or nearly identical.
meiosis I
Reductional division; the first stage of meiotic cell division, in which the number of chromosomes is halved.
A researcher is studying phases of the cell cycle in a population of cells during which there is an increase in the DNA content. This stage is most likely:
S phase
Meiosis function
Sexual reproduction; Production of gametes and spores
Suppose you analyze a time-lapse video of a cell under a microscope, and you observe what appears to be four chromatids tightly aligned along their lengths. Which of the answer choices is an interpretation of this observation?
The chromatids represent a bivalent and the cell is probably in Prophase I of meiosis.
Why are the X and Y chromosomes not considered homologous?
They do not carry the same set of genes.
Meiosis I pairing of homologous chromosomes
Yes
In which phase of mitosis do sister chromatids separate?
anaphase
When do sister chromatids separate in meiosis?
anaphase II
The microtubules that form the mitotic spindle extend out from the centrosome. Where would you expect to find the plus (fast-assembling) end of a spindle microtubule?
away from the centrosome and toward the kinetochore
The process of cell division in a prokaryotic cell is called:
binary fission
Which cellular conditions promote progression of the cell cycle?
binding of cyclins to CDKs; the activation of CDKs; the accumulation of cyclins; the expression and synthesis of cyclin proteins
What cellular process(es) is/are responsible for the increase in protein content associated with the gap phases of the cell cycle?
both transcription and translation
centromere
constriction that physically holds sister chromatids together; the site of the attachment of the spindle fibers that move the chromosome in cell
What are three situations in which mitotic cell division occurs?
in the development of multicellular organisms, maintenance and repair of organs and tissues, and asexual reproduction of unicellular eukaryotes.
Why would a compound that interferes with bacterial cell wall synthesis be useful for treating a bacterial infection?
it would limit growth of the bacterial population through cell division
Meiosis organisms
most eukaryotes
Refer to Animation: Mitotic Cell Division. The contractile ring that leads to cytokinesis in animal cells has been shown to be made primarily of actin filaments (microfilaments). Which motor protein would you predict is involved in contraction of the ring?
myosin
Mitosis Crossing over
no
Mitosis pairing of homologous chromosomes
no
Mitosis separation of homologous chromosomes
no
Refer to Animation: Meiotic Cell Division. During meiosis crossing over takes place between:
non-sister chromatids.
Reproduction by mitotic cell division:
results in two daughter cells that are genetically identical.
Mitosis chromoosmes complement of daughter cell compared with parent cell
same
prophase II
the stage of meiosis II in which the chromosomes in the now-haploid nuclei recondense to their maximum extent.
prophase
the stage of mitosis characterized by the appearance of visible chromosomes.
reductional division
An alternative name for meiosis I, since this division reduces the number of chromosomes by half.
equational division
Another name for meiosis II because cells in meiosis II have the same number of chromosomes at the beginning and at the end of the process.
Mitosis function
Asexual reproduction in unicellular eukaryotes; Development in multicellular eukaryotes; Tissue regeneration and repair in multicellular eukaryotes
non-sister chromatids
Chromatids of different members of a pair of homologous chromosomes; although they carry the same complement of genes, they are not genetically identical.
If you analyze the sequences of the two copies of any of the chromosomes shown in the karyotype, there would be slight sequence differences. What could account for the small differences between a few of the homologous chromosomes? Click to view full size.
Each homologous chromosome in a pair is from a different parent.
miosis II
Equational division; the second stage of meiotic cell division, in which the number of chromosomes is unchanged.
Cytokinesis
Eukaryotic cells, the division of the cytoplasm into two separate cells.
Meiosis _____ is sometimes called reductional division because _____.
I; the number of chromosomes is reduced by half
How does cytokinesis differ between animal and plant cells?
In animal cells, cytokinesis involves a contractile ring made of actin. This contractile ring forms against the inner face of the cell membrane at the equator of the cell. When the ring contracts, the cytoplasm is pinched in half, forming two new daughter cells. In plant cells, cytokinesis involves the growth of a new cell wall called a cell plate in the middle of the dividing cell. The new plate fuses with the original cell wall at the perimeter of the cell and two new daughter cells are formed.
phragmoplast
In dividing plant cells, a structure formed by overlapping microtubules that guide vesicles containing cell wall components to the middle of the cell.
mitosis
In eukaryotic cells, the division of the nucleus, in which the chromosomes are separated into two nuclei.
Suppose you are observing some cells with a microscope, and you see a cell that appears to be dividing. You can see that as the cell starts to pinch in half, the DNA seems to be attached to the plasma membrane via a membrane protein. On further analysis, you find that this organism's DNA is circular - that is, it consists of a closed loop. What can you conclude about this organism and its mode of cell division?
It is a prokaryote that is dividing by binary fission.
What would be the consequence if a cell underwent mitosis but not cytokinesis?
It will become a single cell with two nuclei (and therefore with twice the normal amount of DNA). This type of cell is called a multinucleate cell.
At which stage of the cell cycle could you see sister chromatids with a microscope?
M
Which DNA sequences are more alike: a pair of sister chromatids or a pair of homologous chromosomes?
Sister chromatids are more similar to each other than are homologous chromosomes. Sister chromatids are the result of DNA replication during S phase, so they have identical DNA sequences (with the exception of a few changes that result from rare mutations). Homologous chromosomes are inherited from two different parents. The DNA sequences of these chromosomes are therefore similar, but not identical.
prophase I
The beginning of meiosis I, marked by the visible manifestation of chromosome condensation.
cell cycle
The collective name for the steps that make up eukaryotic cell division.
G0 phase
The gap phase in which cells pause in the cell cycle between M phase and S phase; it may last for periods ranging from days to more than a year.
G1 phase
The gap phase in which the size and protein content of the cell increase and specific regulatory proteins are made and activated in preparation for S-phase DNA synthesis.
G2 phase
The gap phase in which the size and protein content of the cell increase in preparation for M-phase mitosis and cytokinesis.
synapsis
The gene-for-gene pairing of homologous chromosomes in prophase I of meiosis.
s phase
The phase of interphase in which the entire DNA content of the nucleus is replicated.
crossover
The physical breakage, exchange of parts, and reunion between non-sister chromatids.
binary fission
The process by which cells of bacteria or archaeons divide to form two daughter cells.
kinetochores
The protein complexes on a chromatid where spindle fibers attach.
telophase I
The stage of meiosis I in which the chromosomes uncoil slightly, a nuclear envelope briefly reappears, and in many species the cytoplasm divides, producing two separate cells.
metaphase I
The stage of meiosis I in which the meiotic spindle is completed and the bivalents move to lie on an imaginary plane cutting transversely across the spindle.
prometaphase I
The stage of meiosis I in which the nuclear envelope breaks down and the meiotic spindles attach to kinetochores on chromosomes.
anaphase I
The stage of meiosis I in which the two homologous chromosomes of each bivalent separate as they are pulled in opposite directions, but the sister chromatids remained joined at the centromere.
anaphase II
The stage of meiosis II in which the centromere of each chromosome splits and the separated chromatids are pulled toward opposite poles of the spindle.
metaphase II
The stage of meiosis II in which the chromosomes line up so that their centromeres lie on an imaginary plane cutting across the spindle.
telophase II
The stage of meiosis II in which the chromosomes uncoil and become diffuse, a nuclear envelope forms around each set of chromosomes, and the cytoplasm divides by cytokinesis.
prometaphase II
The stage of meiosis II in which the meiotic spindles attach to kinetochores on chromosomes.
metaphase
The stage of mitosis in which the chromosomes are aligned in the middle of the dividing cell.
prometaphase
The stage of mitosis in which the nuclear envelope breaks down and the microtubules of the mitotic spindle attach to chromosomes.
telophase
The stage of mitosis in which the nuclei of the daughter cells are formed and the chromosomes uncoil to their original state.
anaphase
The stage of mitosis in which the sister chromatids separate.
M phase
The stage of the cell cycle consisting of mitosis and cytokinesis, in which the parent cell divides into two daughter cells.
interphase
The time between two successive M phases
sister chromatids
The two copies of a chromosome produced by DNA replication.
An early observation in the study of the development of sea urchin embryos was that there were several enzymes that became active and then inactive in synchrony with the pattern of rapidly repeating cell divisions. These enzymes had a common characteristic in that they phosphorylate (add phosphate groups to) other proteins. Furthermore, they are only active when bound to another protein—ones that vary in abundance at specific times during the cell cycle. These enzymes are:
cyclin dependent kinases (CDK)
A _____ is an enzyme that adds phosphate groups to other proteins. If this enzyme is only active when bound to a specific protein that fluctuates in concentration in synchrony with the cell cycle, then it is a _____.
cyclin; cyclin-dependent kinase
A zygote is:
diploid
Meiosis chromosome complement of daughter cell compared with parent cell
half
Refer to Animation: Meiotic Cell Division. Prophase of meiosis I has some important differences from prophase of mitosis. These differences include: ___________ pair, and _________ occurs.
homologous chromosomes; crossing over
Meiosis I crossing over
yes
Mitosis centromere splitting
yes
Mitosis separation of sister chromatids
yes