3A2 Cell Reproduction and Division Flashcards
Describe how cell reproduction and division of a cell occurs in the processes of mitosis, meiosis, cytokinesis, and binary fission.
Define:
Cell cycle
A series of events that lead to cell division and replication.
It consists of several phases, ensuring that the cell grows, replicates its DNA, and divides properly.
What are the 5 phases of the cell cycle?
- G0 (Resting Phase)
- G1 (Cell Growth)
- S (DNA Replication)
- G2 (Preparation Phase)
- M (Cell Divsion/Mitosis)
Each phase of the cell cycle has a different function in the life of the cell.
Fill in the blank:
The G0 phase is a ________ phase where cells are not actively dividing.
resting
Cells in this phase are in a dormant state and may not proceed through the cell cycle unless triggered by specific signals.
What happens during the G1 phase?
The cell grows and prepares for DNA replication.
The cell increases in size and synthesizes proteins and organelles in preparation for DNA synthesis in the next phase, the S phase.
What happens during the S phase of the cell cycle?
DNA replication
In this phase, the entire DNA content of the cell is duplicated, ensuring that each daughter cell will have a complete set of chromosomes.
Fill in the blank:
The G2 phase ensures that ______ is intact before mitosis.
DNA
The G2 phase ensures DNA integrity by proofreading and repairing errors before cell division. Any errors in DNA would be copied when the cell divides, so this step is imperative.
What happens if errors are found during G2?
The cell repairs the DNA or halts division.
The G2 checkpoint ensures that any DNA damage is fixed before mitosis begins.
What is produced during the G2 phase?
Proteins and organelles for cell division.
The G2 phase produces structures like microtubules needed for mitosis.
Which phase directly follows the G2 phase?
M phase
(Mitosis)
Define:
Mitosis
The process of cell division that results in two identical daughter cells.
It ensures that each daughter cell has the same number and type of chromosomes as the original cell.
List the steps of mitosis in order.
- Prophase
- Prometaphase
- Metaphase
- Anaphase
- Telophase
Following telophase, the cells physically divide through cytokinesis. Some scientists consider cytokinesis as part of mitosis, while others consider it a separate process.
What happens in the Prophase step of mitosis?
Chromosomes condense and the mitotic spindle is formed.
This first step prepares the chromosomes for separation by condensing them into very small X-shaped structures. The centrosomes of the cell move to opposite sides, initiating the formation of the mitotic spindle.
Define
Prometaphase
The second stage of mitosis where the nuclear envelope breaks down and kinetochores are formed.
In this phase, the chromosomes attach to the mitotic spindles. The site where chromosomes attach to the spindle is known as the kinetochore.
Describe what happens in the Metaphase stage of mitosis.
The chromosomes line up at the metaphase plate and fully attach to the mitotic spindles.
The metaphase plate is not a real structure, but refers to the region in the middle of the cell where the chromosomes line up.
What happens in the Anaphase step of mitosis?
Sister chromatids separate and are pulled to opposite ends of the cell by the mitotic spindle.
The proteins that held together the chromatids break down, allowing for the separation and movement of the individual chromatids.
True or False:
The nuclear envelope is fully reformed during anaphase.
False
Anaphase is when the sister chromatids are pulled apart. The nuclear envelope reforms during telophase.
What phase involves chromosomes de-condensing and the nuclear envelope re-forming?
Telophase
This phase marks the near end of mitosis, where the cell prepares to divide into two.
What is the role of spindle fibers during mitosis?
The attach to centromeres and pulls chromatids apart during separation.
These fibers are crucial for ensuring that each daughter cell receives an equal set of chromosomes.
True or False:
Mitosis results in genetic variation between the daughter cells.
False
This process produces genetically identical daughter cells, ensuring that the genetic material is faithfully copied and distributed.
Fill in the blank:
After telophase, the cell undergoes ________ to complete division.
cytokinesis
Cytokinesis physically separates the cytoplasm of the two daughter cells, finalizing the division process after mitosis.
True or False:
During telophase, the chromosomes begin to de-condense, and a new nuclear envelope forms.
True
Near the end of mitosis, the nuclear envelope reforms around the chromosomes, and the chromatin begins to unwind.
What is meiosis?
The process of cell division that produces four non-identical gametes.
This process reduces the chromosome number by half, ensuring genetic diversity in offspring.
What type of cells are produced by meiosis?
Gametes
(sperm and egg cells)
The process creates haploid cells, each containing half the chromosome number of the original diploid cell.
What is a haploid cell?
A cell with half the number of chromosomes.
Haploid cells (like gametes) are produced during meiosis and contain one set of chromosomes.
What is a diploid cell?
A cell with two complete sets of chromosomes.
Somatic cells are diploid, meaning they have two sets of chromosomes, one from each parent.
True or False:
The purpose of meiosis is to produce gametes with half the chromosome number for sexual reproduction.
True
This process ensures genetic variation and allows for fertilization to restore the diploid number of chromosomes.
How many divisions occur in meiosis?
Two
Meiosis I reduces the chromosome number, and Meiosis II divides the chromosomes into four unique gametes.
What are the phases of Meiosis I?
- Prophase I
- Metaphase I
- Anaphase I
- Telophase I
This first round of cell division is similar to mitosis, but difers in that the resulting daughter cells half have the chromosomes of the parent cell.
What are the phases of Meiosis II?
- Prophase II
- Metaphase II
- Anaphase II
- Telophase II
Following Telophase II, the daughter cells undergo cytokinesis to split into the final product, 4 haploid cells.
Fill in the blank:
________ _____ is the exchange of genetic material between homologous chromosomes.
Crossing over
Crossing over occurs during prophase I of meiosis and increases genetic diversity.
What is anaphase I in meiosis?
The homologous chromosomes are pulled toward opposite poles.
In anaphase I, the chromosome pairs separate, reducing the chromosome number by half.
What is telophase I in meiosis?
The chromosomes arrive at opposite poles, and the cell starts to divide.
Telophase I concludes meiosis I, leading to the formation of two haploid cells.
What phase separates the sister chromatids of each chromosome?
Meiosis II
Meiosis II is similar to mitosis but with haploid cells as the starting point.
What happens in prophase II of meiosis?
Chromosomes condense, and the nuclear membrane dissolves.
Prophase II prepares the haploid cells for the separation of sister chromatids.
True or False:
Chromosomes align at the cell’s equator during metaphase II of meiosis.
True
Similar to metaphase in mitosis, this step ensures chromosomes will be evenly split.
Fill in the blank:
During anaphase II of meiosis, ________ _________ are pulled to opposite poles of the cell.
sister chromatids
Anaphase II ensures that each new cell will receive one chromatid from each chromosome.
What is synapsis in meiosis?
The pairing of homologous chromosomes during prophase I.
Synapsis is crucial for crossing over and the proper alignment of chromosomes for meiosis.
What is the role of spindle fibers in meiosis?
They help separate chromosomes during cell division.
These form during both meiosis I and meiosis II to guide chromosome movement.
Define:
Cytokinesis
The process where the cytoplasm of a parental cell divides into two daughter cells.
This process usually occurs after mitosis or meiosis, completing cell division and resulting in two distinct cells.
What marks the end of cytokinesis?
The formation of two separate daughter cells.
The two daughter cells have their own cytoplasm, organelles, and membrane.
What structure forms in plant cells during cytokinesis?
The cell plate.
In plant cells, the cell plate forms in the middle and eventually develops into the cell wall, separating the two daughter cells.
True or False:
Cytokinesis occurs before mitosis.
False
Cytokinesis occurs after mitosis or meiosis, finalizing the division of the cell into two daughter cells.
Fill in the blank:
In animal cells, cytokinesis involves the formation of a _________ _________.
cleavage furrow
This pinches the cell membrane in two, eventually splitting the cell into two daughter cells.
What forms during the process of cleavage furrow formation?
A contractile ring of actin filaments.
This helps to tighten and pinch the membrane, leading to the division of the cell’s cytoplasm.
What happens if cytokinesis does not occur properly?
It can lead to multinucleated cells or cell division errors.
This can result in cells with more than one nucleus or other cell division abnormalities.
What is a multinucleated cell?
A cell with more than one nucleus due to incomplete cytokinesis.
They can result from failed cytokinesis, where the division of the cytoplasm doesn’t occur correctly.
True or False:
Cytokinesis is the final stage of cell division.
True
Cytokinesis marks the final step of cell division, ensuring the formation of two daughter cells.
Fill in the blank:
During cytokinesis, the ______ _______ moves toward the center of the dividing cell in plant cells.
cell plate
The cell plate grows in the center of the plant cell and eventually fuses with the membrane to separate the daughter cells.
What is binary fission?
Asexual reproduction where one cell divides into two identical cells.
It is common in prokaryotes like bacteria and some single-celled eukaryotes, enabling rapid population growth.
What is the main advantage of binary fission?
It allows for rapid reproduction.
This process enables prokaryotes to quickly increase their population in favorable conditions.
What is the first step in binary fission?
DNA replication
Before a cell can divide, it must replicate its DNA so each daughter cell receives an identical copy.
True or False:
Binary fission requires a partner organism.
False
Binary fission is an asexual process, meaning it does not require a mate for reproduction.
Fill in the blank:
Binary fission is most commonly observed in __________.
prokaryotes
Bacteria and archaea use binary fission as their primary mode of reproduction.
What happens to the replicated DNA during binary fission?
It moves to the opposite sides of the cell.
This step ensures that each daughter cell inherits one copy of the DNA.
What is the dividing structure in bacterial binary fission?
The septum
The septum is a dividing wall formed during binary fission that separates the two daughter cells.
True or False:
Binary fission is faster than mitosis.
True
This is a simpler and quicker process compared to mitosis because it does not involve a complex nucleus.
Fill in the blank:
Binary fission produces __________ copies of the parent cell.
identical
The daughter cells have identical genetic material unless a mutation occurs during DNA replication.
How does binary fission benefit pathogenic bacteria?
It allows them to rapidly infect a host.
Bacteria like Salmonella or E. coli use binary fission to multiply quickly, increasing their ability to spread and cause disease.
Why is binary fission important in microbiology?
It explains how microorganisms reproduce and grow.
Understanding binary fission helps scientists study bacterial behavior, antibiotic resistance, and disease transmission.
