What are the dimensions of a centriole?
Click to see answer
Approximately 500 nm long and 200 nm in diameter.
Click to see question
What are the dimensions of a centriole?
Approximately 500 nm long and 200 nm in diameter.
What triggers programmed cell death (apoptosis) if DNA damage is extensive?
The protein p53.
What does the G2 checkpoint check for?
DNA integrity and successful DNA replication.
What is cytokinesis?
The division of the cytoplasm into two parts, each enclosing one of the newly formed nuclei.
What are the four phases of mitosis?
Prophase, metaphase, anaphase, and telophase.
What are nonkinetochore microtubules?
Spindle fibres that extend from one pole to the opposite pole.
What is the significance of the mitotic cell cycle?
It is important for growth, repair, and asexual reproduction.
What do nonkinetochore microtubules interact with during cell division?
Nonkinetochore microtubules from the opposite pole of the cell.
What do the contents of Golgi vesicles contribute to in plant cells during cytokinesis?
They contribute to the cell wall of the daughter cell.
What happens to sister chromatids when colchicine is used?
They remain attached in the metaphase plate.
What can result from the dysregulation of checkpoints in the cell division process?
Uncontrolled cell division and cancer.
What are kinetochore microtubules?
Spindle fibres that attach specifically to the kinetochores.
What are sister chromatids?
Identical copies of a chromosome joined at the centromere.
Where are the centrosomes located during metaphase?
At opposite poles of the cell.
What are chromosomes made of after DNA replication in the S phase?
Two sister chromatids.
What do microtubules form during prophase?
Spindle fibres.
What are spindle fibres that do not attach to kinetochores called?
Nonkinetochore microtubules.
What is the role of nonkinetochore microtubules in a dividing animal cell?
They are responsible for elongating the whole cell during anaphase.
What does the Cell Theory state?
The cell is a fundamental unit of structure, function, and organization in all living organisms, and new cells are formed from existing cells.
What happens to chromatin during the first stage of mitosis?
It condenses into chromosomes.
What lies on the metaphase plate during metaphase?
The centromeres of the chromosomes.
How is mitosis related to asexual reproduction?
Mitosis is the basis of asexual reproduction, allowing for the production of offspring without the fusion of gametes.
Why is the proper arrangement of chromosomes important during mitosis?
Proper arrangement along the equator ensures equal sharing of chromosomes between daughter nuclei as sister chromatids are pulled to opposite poles.
What do sister chromatids become after separation in Anaphase?
Each chromatid becomes a full-fledged chromosome.
How does cytokinesis occur in animal cells?
A cleavage furrow develops in the cell membrane, which eventually joins up to separate the two daughter nuclei.
What happens to genetic material during prophase?
It becomes visible as chromosomes due to condensation of chromatin.
What happens to the cell plate in plant cells during cytokinesis?
It eventually fuses with the parent cell wall and membrane, separating the two daughter cells.
What do spindle fibres originate from?
Long protein fibres (microtubules) that extend from the centrioles at the beginning of nuclear division.
What are kinetochore microtubules?
Spindle fibres that attach to the kinetochores of the chromosomes.
What occurs to sister chromatids during mitosis?
They separate and move into the two daughter nuclei.
Why are cell cycle checkpoints important?
They ensure the cell only proceeds to the next phase if the previous phase is properly completed.
What does the G1 checkpoint assess?
Cell size, nutrient availability, DNA integrity, and molecular signals.
When does cytokinesis usually begin?
By late telophase.
What structure forms in plant cells during cytokinesis?
A cell plate forms from a series of Golgi vesicles.
What is colchicine used for in cell division?
To prevent the formation of spindle fibres in actively dividing cells.
What is the role of the anaphase promoting complex (APC)?
APC transmits the go-ahead signal and removes inhibitors of a protease that digests cohesin.
What is an aster?
A star-shaped structure formed by short microtubules developing from centrioles.
How do spindle fibres contribute to chromatid separation?
By shortening through the removal of tubulin subunits, they pull chromatids to opposite poles.
What is the duration of Anaphase in mitosis?
Anaphase is the shortest stage, often lasting only a few minutes.
What happens to the spindle fibres during Telophase?
Spindle fibres disintegrate.
What happens during cytokinesis?
The cell membrane pinches in to divide the cytoplasm into two daughter cells.
What are centrioles?
Microtubule-based cylinders found in animal cells, composed of 9 triplets of microtubules.
What is the cell cycle?
An ordered sequence of events in cell division.
What percentage of the cell cycle does interphase account for?
About 90%.
What occurs during the G1 phase?
Cell synthesizes organelles, builds energy stores, and manufactures proteins.
What is the main activity during the G2 phase?
The cell continues to store energy and manufacture proteins and organelles.
What happens if DNA damage is detected at the G2 checkpoint?
The cell can stall the cycle to allow for DNA repairs.
What is the composition of a centrosome in animal cells?
Each centrosome is composed of two centrioles positioned perpendicular to each other.
What does the M checkpoint check for?
It checks that all chromosomes are attached to spindle fibers and that proper tension is on the paired kinetochores.
What can be observed as a result of using colchicine?
The number and structure of chromosomes, as well as karyotyping.
How does mitosis contribute to the growth of multicellular organisms?
Mitosis allows multicellular eukaryotes to develop from a single cell, enabling growth from a fertilized egg into an adult organism.
What happens to nonkinetochore microtubules during metaphase?
They overlap at the metaphase plate.
What does each daughter cell receive after mitosis?
An identical set of chromosomes as the parent cell.
What shape do chromosomes take during Anaphase?
A distinct V-shape.
What are the main stages of the mitotic cell cycle?
The main stages include prophase, metaphase, anaphase, and telophase.
What are centrosomes?
Nonmembranous organelles found only in animal cells that function as the microtubule organizing center (MTOC).
How is genetic material organized during the cell cycle?
It condenses into chromosomes during mitosis and is replicated during interphase.
What form does genetic material take during interphase?
Chromatin.
What happens to centrosomes in animal cells during prophase?
They move to opposite ends of the cell.
What causes the nuclear envelope to disintegrate during prophase?
Phosphorylation of various proteins on the inner surface of the nuclear envelope.
What is the kinetochore?
A specialized protein structure that assembles at the centromere of the chromosome.
What happens to the centromere during Anaphase?
The centromere of each chromosome divides, allowing sister chromatids to separate.
Why is it important to tightly regulate the mitotic cell cycle?
Tight regulation is necessary to maintain genetic stability and ensure proper growth, repair, and reproduction processes.
What happens to chromosomes during Telophase?
They reach their respective poles and become the genetic material of daughter nuclei.
What is the role of centrosomes and centrioles during mitosis?
They help organize the spindle fibers that separate chromosomes.
What is M-phase-promoting factor (MPF) and its role?
MPF is a growth factor that must be present for the cell cycle to proceed; it disintegrates the nuclear envelope and activates kinases.
How long does metaphase typically last?
About 20 minutes.
What is the shortest part of the cell cycle?
The mitotic (M) phase, which includes both mitosis and cytokinesis.
What are the three main stages of interphase?
G1, S, and G2 phases.
What happens during the S phase?
DNA replication/synthesis occurs, and the centrosome is duplicated.
What ensures that cells can proceed to the M phase?
Only cells with the right conditions can proceed to ensure that damaged or incomplete DNA is not passed on.
What occurs to the nucleolus during prophase?
The nucleolus disappears.
What is the diameter of spindle fibres?
About 24-25 nm.
What is the role of the centromere in mitotic chromosomes?
It attaches the two sister chromatids together.
What is a cell cycle checkpoint?
A critical control point where stop and go-ahead signals regulate the cell cycle.
How many major checkpoints are there in the cell cycle?
Three major checkpoints found in the G1, G2, and M phases.
What is the G0 phase?
A non-dividing state where most cells in the human body are found.
What is the metaphase plate?
An imaginary plane that is equidistant between the spindle's two poles where chromosomes align.
What role does mitosis play in the repair of the body?
Mitosis is essential for repairing worn-out parts of the body.
What is the process that ensures daughter nuclei receive the same number of chromosomes as the parent nucleus?
Semi-conservative replication of DNA must occur before mitosis, duplicating each chromosome into two identical sister chromatids.
What role does the mitotic spindle play in mitosis?
The mitotic spindle is crucial for the proper separation of chromosomes during mitosis.
What reforms around the chromosomes at each pole during Telophase?
The nuclear envelope reforms.
What is the significance of mitosis in terms of genetic identity?
Mitosis ensures that the two daughter nuclei contain genetically identical sets of chromosomes as the parent nuclei, making daughter cells clones of the parent cell.
What is the role of spindle fibres during metaphase?
Kinetochore microtubules attach to kinetochores at the centromere of each chromosome.
What happens to sister chromatids once they are separated?
They are considered individual chromosomes.
What do checkpoints monitor in the cell cycle?
DNA replication, DNA damage, and chromosome-to-spindle attachments.
What occurs to the cell during Anaphase?
The cell elongates as nonkinetochore microtubules lengthen.
What occurs to the chromosomes at the end of Telophase?
They uncoil and return to their chromatin form.
What are the two main processes that occur during the M phase?
Mitosis (nuclear division) and cytokinesis.
How do daughter chromosomes move during Anaphase?
They move, centromere first, to opposite poles of the spindle due to shortening of spindle fibres.
What happens if a cell does not receive a growth signal at the G1 checkpoint?
It exits the cell cycle and switches to a non-dividing state called G0.
What reappears in each new nucleus during Telophase?
The nucleolus reappears.
