The cell cycle Flashcards
Why do cells replicate?
Cells replicate to replace those that die due to chemicals, burns, or damage.
What is the limit on the number of times a cell can divide in its lifetime?
Cells can divide 50 times in their lifetime.
What happens to chromosomes during cell division?
Chromosomes erode at their ends during each division, leading to cell aging.
What is the primary difference in cell division between single-celled and multicellular organisms?
In multicellular organisms like humans, cells require adequate contents to survive and divide.
What are the phases of the cell cycle?
The phases are G1, S, G2, mitosis, and cytokinesis.
What occurs during the G1 phase of the cell cycle?
Cells swell in size and increase membrane and cytoplasm.
What is the purpose of the S phase in the cell cycle?
The S phase is for the synthesis of DNA, making two copies of it.
What is the role of checkpoints in the cell cycle?
Checkpoints ensure the size, quality of DNA, and sufficient nutrients for new cells.
True or False: Neurons can replace themselves.
False
What is asexual reproduction?
Asexual reproduction creates genetically identical cells, though not always perfectly.
What are the five phases of mitosis?
- Prophase
- Prometaphase
- Metaphase
- Anaphase
- Telophase
What is the outcome of meiosis?
Meiosis produces haploid cells with half the genetic material.
What is recombination, and when does it occur?
Recombination occurs during Prophase I of meiosis and allows genetic material to be exchanged.
What happens during Anaphase I of meiosis?
Homologous chromosomes are pulled apart toward opposite poles.
What is the difference between Meiosis I and Meiosis II?
Meiosis I reduces the chromosome number by half, while Meiosis II separates chromatids.
What is the role of Sertoli cells during spermatogenesis?
Sertoli cells provide nutrition and support to developing sperm.
Fill in the blank: The first step in meiosis is the _______.
duplication of chromosomes.
What is a bivalent in meiosis?
A bivalent is a paired chromosome structure formed during Prophase I.
What is the result of cytokinesis during Telophase I?
Cytokinesis results in two haploid daughter cells.
What occurs during Telophase II of meiosis?
Cleavage furrow develops, cytokinesis follows, and the nuclear envelope forms.
How many haploid daughter cells result from one complete meiosis process?
Four haploid daughter cells.
What is the significance of genetic diversity in meiosis?
Genetic diversity facilitates evolution and reduces the risk of genetic diseases wiping out populations.
What is the first phase of Meiosis I?
Prophase I
What are the four phases of Meiosis I?
- Prophase I
- Metaphase I
- Anaphase I
- Telophase I
What are the four phases of Meiosis II?
- Prophase II
- Metaphase II
- Anaphase II
- Telophase II
In Meiosis, each starting diploid cell contains how many copies of each chromosome?
2 copies
What is the significance of interphase in meiosis?
Chromosome duplication occurs
How does Prophase I in meiosis compare to prophase in mitosis?
Virtually identical
What structures form during Prophase I?
- Spindle development
- Breakdown of membrane
- Centrosomes move towards poles
What are paired chromosomes in Prophase I called?
Bivalents (or tetrads)
What are chiasmata?
Areas where crossing over occurred and chromosomes remain attached
What is a critical difference between mitosis and meiosis during Metaphase I?
Random orientation of chromosomes
What happens during Anaphase I?
- Kinetochore spindle fibers contract
- Homologous pairs are pulled apart
- Chromosomes move to separate poles
What is the ploidy of daughter cells after Telophase I?
Haploid
What typically happens to the nuclear envelope during Telophase I?
Usually not reformed
What is the relationship between Meiosis II and mitosis?
Meiosis II is similar to mitosis
What occurs to chromatids during Meiosis II?
Chromatids are no longer identical due to recombination
What happens during Prophase II?
A new set of spindle fibers forms
Where do chromosomes align during Metaphase II?
Metaphase plate
What happens to centromeres during Anaphase II?
Centromeres split
What type of cells does Meiosis II produce?
4 haploid (n) daughter cells
Fill in the blank: During Telophase II, chromosomes begin to fade and become ______.
granular chromatin
