Prophase
What is the primary role of prophase in mitosis?
Prophase is the first stage of mitosis, during which chromatin condenses into visible chromosomes, the mitotic spindle begins to form, and the nuclear envelope starts to break down.
What key event marks the beginning of prometaphase in mitosis?
The breakdown of the nuclear envelope marks the beginning of prometaphase, allowing spindle fibers to access the chromosomes
What is the defining characteristic of metaphase in mitosis?
In metaphase, the chromosomes align along the metaphase plate, an imaginary plane equidistant from the two spindle poles
What is the primary event that occurs during anaphase in mitosis?
Sister chromatids are separated and pulled toward opposite poles of the cell by the shortening of spindle fibers
What happens to the nuclear envelope during telophase?
The nuclear envelope re-forms around each set of separated chromosomes, creating two distinct nuclei in the cell
How do the chromosomes change during prophase?
During prophase, the chromatin condenses and coils tightly to form distinct, visible chromosomes, each consisting of two sister chromatids connected at the centromere.
How do chromosomes interact with the mitotic spindle during prometaphase?
During prometaphase, spindle fibers attach to the kinetochores, which are protein complexes located at the centromeres of each chromosome
How are chromosomes positioned during metaphase, and why is this important?
Chromosomes are aligned at the metaphase plate, ensuring that each sister chromatid is equidistant from both poles, which is crucial for their equal distribution during anaphase
What happens to the centromeres of the chromosomes during anaphase?
The centromeres split, allowing the sister chromatids to separate and become individual chromosomes
What is the main function of cytokinesis, and how does it differ from telophase?
Cytokinesis divides the cytoplasm and organelles into two daughter cells, completing cell division, whereas telophase focuses on re-establishing the nuclei
What role do centrosomes play during prophase?
The centrosomes move to opposite poles of the cell and begin forming the mitotic spindle, which is essential for the separation of chromosomes during later stages of mitosis
What is the role of kinetochores in prometaphase?
Kinetochores serve as the attachment points for spindle fibers and help facilitate the movement of chromosomes during mitosis
What role do spindle fibers play in metaphase?
Spindle fibers attached to kinetochores exert tension to align the chromosomes at the metaphase plate and prepare for their separation
How do spindle fibers facilitate chromosome movement during anaphase?
Spindle fibers attached to kinetochores shorten, pulling the chromosomes toward opposite poles, while non-kinetochore microtubules elongate to push the poles further apart
How is the mitotic spindle affected during telophase?
The mitotic spindle disassembles as its role in segregating chromosomes is complete
What happens to the nuclear envelope during prophase?
The nuclear envelope begins to break down, allowing the chromosomes to interact with the spindle fibers
What happens to the chromosomes during prometaphase?
The chromosomes begin to move toward the cell's equatorial plane, or metaphase plate, as they are pulled and aligned by the spindle fibers
How does the cell ensure that all chromosomes are properly aligned during metaphase?
The spindle assembly checkpoint monitors the attachment of spindle fibers to kinetochores and ensures all chromosomes are correctly aligned before progressing to anaphase
Why is the separation of sister chromatids during anaphase important?
It ensures that each daughter cell will receive an identical set of chromosomes, maintaining genetic consistency
What structures are involved in cytokinesis in animal and plant cells?
In animal cells, a contractile ring forms to split the cell. In plant cells, a cell plate forms from vesicles, eventually becoming the new cell wall
What structures start to form during prophase, and what is their function?
The mitotic spindle, made of microtubules, starts to form. Its function is to attach to chromosomes and help segregate them into the daughter cells
What is the significance of spindle fibers attaching to chromosomes in prometaphase?
The attachment ensures that each sister chromatid will be pulled toward opposite poles of the cell, enabling proper chromosome segregation during anaphase
What would happen if a chromosome failed to align correctly during metaphase?
If a chromosome fails to align correctly, the spindle assembly checkpoint may delay the progression to anaphase to prevent unequal distribution of genetic material, which could lead to errors
What might happen if the sister chromatids do not separate properly during anaphase?
If sister chromatids fail to separate correctly, it can lead to aneuploidy, where daughter cells have an abnormal number of chromosomes, potentially causing genetic disorders or cell malfunction
What key structural changes occur to the chromosomes during telophase?
During telophase, the chromosomes begin to decondense and return to their chromatin form, becoming less visible under a microscope