Cellular Reproduction
cell CYCLE
Author: Xanat Vaitiare Ferreyro Davis Date: April, 2022
Cell division
Cell division is the only way single-celled organisms can reproduce. Multicellular organisms need cell division to grow and to replace dead or damaged cells.
Cells divide, differentiate, or die
Division
Differentiation
apoptosis
Cells stop dividing to specialize in structure and function, a process called differentiation. Once differentiated, some cells may divide again under certain conditions.
Cells divide to produce two identical daughter cells.
Cells can also undergo programmed cell death, or apoptosis, a process that eliminates unnecessary cells during development and removes unhealthy or damaged cells in the mature organism.
Cell Cycle Overview
Cell division occurs in this phase
Growth phase
Cell reproduction occurs in a sequence of phases that include growth, DNA replication, growth and preparation for mitosis, and finally mitosis or cell division. "Cell cycle regulators" are molecular signals that may stimulate or halt cell division, instruct cells to differentiate, or initiate cell death. If regulators don’t function properly, an organism may end up with too few or too many cells.
Differentiation phase
Cell cycle regulators
Growth and preparation for division phase
DNA replication phase
Interphase and mitosis
A dividing cell repeatedly cycles through interphase and mitosis; in other words, it goes through cycles of growth and division.
Together, G1, S, and G2 make up interphase: the period during which a cell grows and replicates its DNA.
The M phase or Mitosis is the period in which a cell divides into two daughter cells, each with a complete set of chromosomes.
G1 Phase
First Gap Phase: During G1, the cell increases in size and prepares to replicate its DNA. G1-Checkpoint: Rest or Divide?If the DNA is undamaged and enough resources are available for the cell to keep growing and dividing. If the DNA is damaged or there aren't enough resources, either the cell differentiates, dies or it enters a resting state (G0 phase).Checklist Summary:✓ No DNA damage.✓ Sufficient resources.
G0 Phase
Zero Gap Phase: A cell can "exit" the cell cycle when it receives a signal to differentiate, or when resources are insufficient to grow and divide. Whether or not a cell exits the cell cycle depends on the organism’s stage in development, the type of cell, and the resources available.
S Phase
Synthesis Phase: The cell replicates its DNA. At the end of this phase, the cell has two complete sets of chromosomes. S-Checkpoint: DNA OK?If DNA synthesis progresses without errors, growth signals will stimulate the cell to proceed to G2, during which the cell matures. Checklist Summary:✓ No errors during DNA replication.
G2 Phase
Second Gap Phase: The cell continues to grow and prepares for division. G2-Checkpoint: Fully Equipped?To proceed to the next phase, all chromosomes have to be fully replicated and contain no other types of damage. Only then can it enter mitosis, or the M phase, and divide. Checklist Summary: ✓ DNA without damage.✓ Chromosome set complete.✓ Enough cell components.
M Phase
Mitosis Phase: In this last phase of the cell cycle, the cell stops growing and divides into two daughter cells, each with the same number of chromosomes. M-Checkpoint:Are Any Sister Chromatids Unattached?For mitosis to proceed correctly, the two copies in a duplicated chromosome (each called a sister chromatid) should both be correctly separated, becoming two chromosomes. Checklist Summary: ✓ All sister chromatids are separated at the centromere.
Formative activity: Quiz: Eukaryotic cell cycle
Mitosis
Mitosis is the cell division mechanism that maintains the number of chromosomes producing 2 identical daughter cells or clones.
Mitosis
Prophase:
Metaphase:
Anaphase:
Telophase:
Early prophase:
The duplicated chromosomes become visible as they condense. Centrosomes move to the opposite side of the cells as the nuclear envelope breaks. Spindle microtubules attach sister chromatids to centrosomes.
Mitosis begins as DNA replication stops. The chromosomes begin to apprear grainy as they start to condense. The nuclear envelope begins to break uo and the chromosome gets duplicated.
All of the chromosomes are aligned midway between the spindle poles.
Spindle microtubules separate the sister chromatids and move them toward opposite spindle poles. Each sister chromatid has now become and individual, undiplicated chromosome.
The chromosomes reach opposite sides of the cell and loosen up. Mitosis ends when a new nuclear envelope forms around each cluster of chromosomes.
Video
Formative activity: Mitosis matchup
Meiosis
Meiosis is the cell division mechanism that halves the number of chromosomes producing 4 different daughter cells or gametes.
Meiosis Overview
- Meiosis division in cells produces egg cells (female gametes) or sperm cells (male gametes).
- To produce haploid gametes (n), cells undergo two cellular divisions similar to mitosis.
- During meiosis I, homologous chromosomes separate into different nuclei.
- During meiosis II, chromatid sisters separate into unduplicated chromosomes.
Meiosis 1
Metaphase I:
Anaphase I:
Prophase I:
Telophase I:
Homologous chromosome pairs are aligned between spindle poles. Spindle microtubules have attached the two chromosomes of each pair to opposite spindle poles.
Homologous chromosomes condense, pair up, and swap segments. Spindle microtubules attach to them as the nuclear envelope breaks up.
Homologous chromosomes separate and begin moving toward the spindle poles.
A complete set of chromosomes clusters at each spindle pole. A nuclear envelope forms around each set, so two haploid (n) nuclei form.
II
Meiosis II
Metaphase II:
Anaphase II:
Telophase I:
Prophase II:
the chromosomes are aligned midway between spindle poles. Spindle microtubules have attached theis sister chromatids to opposite spindle poles.
The chromosomes condense. Spindle microtubules attach to each sister chromatid as the nuclear envelope breaks up.
Sister chromatids separate and move toward opposite spindle poles. When sister chromosomes separete, each becomes an individual chromosome.
A complete set of chromosomes clusters at each spindle pole. A nuclear envelope forms around each set, so four haploid (n) nuclei form.
Crossing over
- During prophase I, homologous chromosomes align and exchange genetic information in a process called Crossing over.
- This process ensures genetic variability.
- Close contact between homologous chromosomes promotes crossing over, in which non-sister chromatids exchange corresponding pieces.
Mitosis vs Meiosis
Formative activity: Meiosis flipbook
Thanks
Adapted from: HHMI (n.d.) The Eukaryotic cell cycle and Cancer. Biointeracitve. https://media.hhmi.org/biointeractive/click/cellcycle/ by Xanat Vaitiare Ferreyro Davis
Sum22: Cell cycle
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Transcript
Cellular Reproduction
cell CYCLE
Author: Xanat Vaitiare Ferreyro Davis Date: April, 2022
Cell division
Cell division is the only way single-celled organisms can reproduce. Multicellular organisms need cell division to grow and to replace dead or damaged cells.
Cells divide, differentiate, or die
Division
Differentiation
apoptosis
Cells stop dividing to specialize in structure and function, a process called differentiation. Once differentiated, some cells may divide again under certain conditions.
Cells divide to produce two identical daughter cells.
Cells can also undergo programmed cell death, or apoptosis, a process that eliminates unnecessary cells during development and removes unhealthy or damaged cells in the mature organism.
Cell Cycle Overview
Cell division occurs in this phase
Growth phase
Cell reproduction occurs in a sequence of phases that include growth, DNA replication, growth and preparation for mitosis, and finally mitosis or cell division. "Cell cycle regulators" are molecular signals that may stimulate or halt cell division, instruct cells to differentiate, or initiate cell death. If regulators don’t function properly, an organism may end up with too few or too many cells.
Differentiation phase
Cell cycle regulators
Growth and preparation for division phase
DNA replication phase
Interphase and mitosis
A dividing cell repeatedly cycles through interphase and mitosis; in other words, it goes through cycles of growth and division.
Together, G1, S, and G2 make up interphase: the period during which a cell grows and replicates its DNA.
The M phase or Mitosis is the period in which a cell divides into two daughter cells, each with a complete set of chromosomes.
G1 Phase
First Gap Phase: During G1, the cell increases in size and prepares to replicate its DNA. G1-Checkpoint: Rest or Divide?If the DNA is undamaged and enough resources are available for the cell to keep growing and dividing. If the DNA is damaged or there aren't enough resources, either the cell differentiates, dies or it enters a resting state (G0 phase).Checklist Summary:✓ No DNA damage.✓ Sufficient resources.
G0 Phase
Zero Gap Phase: A cell can "exit" the cell cycle when it receives a signal to differentiate, or when resources are insufficient to grow and divide. Whether or not a cell exits the cell cycle depends on the organism’s stage in development, the type of cell, and the resources available.
S Phase
Synthesis Phase: The cell replicates its DNA. At the end of this phase, the cell has two complete sets of chromosomes. S-Checkpoint: DNA OK?If DNA synthesis progresses without errors, growth signals will stimulate the cell to proceed to G2, during which the cell matures. Checklist Summary:✓ No errors during DNA replication.
G2 Phase
Second Gap Phase: The cell continues to grow and prepares for division. G2-Checkpoint: Fully Equipped?To proceed to the next phase, all chromosomes have to be fully replicated and contain no other types of damage. Only then can it enter mitosis, or the M phase, and divide. Checklist Summary: ✓ DNA without damage.✓ Chromosome set complete.✓ Enough cell components.
M Phase
Mitosis Phase: In this last phase of the cell cycle, the cell stops growing and divides into two daughter cells, each with the same number of chromosomes. M-Checkpoint:Are Any Sister Chromatids Unattached?For mitosis to proceed correctly, the two copies in a duplicated chromosome (each called a sister chromatid) should both be correctly separated, becoming two chromosomes. Checklist Summary: ✓ All sister chromatids are separated at the centromere.
Formative activity: Quiz: Eukaryotic cell cycle
Mitosis
Mitosis is the cell division mechanism that maintains the number of chromosomes producing 2 identical daughter cells or clones.
Mitosis
Prophase:
Metaphase:
Anaphase:
Telophase:
Early prophase:
The duplicated chromosomes become visible as they condense. Centrosomes move to the opposite side of the cells as the nuclear envelope breaks. Spindle microtubules attach sister chromatids to centrosomes.
Mitosis begins as DNA replication stops. The chromosomes begin to apprear grainy as they start to condense. The nuclear envelope begins to break uo and the chromosome gets duplicated.
All of the chromosomes are aligned midway between the spindle poles.
Spindle microtubules separate the sister chromatids and move them toward opposite spindle poles. Each sister chromatid has now become and individual, undiplicated chromosome.
The chromosomes reach opposite sides of the cell and loosen up. Mitosis ends when a new nuclear envelope forms around each cluster of chromosomes.
Video
Formative activity: Mitosis matchup
Meiosis
Meiosis is the cell division mechanism that halves the number of chromosomes producing 4 different daughter cells or gametes.
Meiosis Overview
Meiosis 1
Metaphase I:
Anaphase I:
Prophase I:
Telophase I:
Homologous chromosome pairs are aligned between spindle poles. Spindle microtubules have attached the two chromosomes of each pair to opposite spindle poles.
Homologous chromosomes condense, pair up, and swap segments. Spindle microtubules attach to them as the nuclear envelope breaks up.
Homologous chromosomes separate and begin moving toward the spindle poles.
A complete set of chromosomes clusters at each spindle pole. A nuclear envelope forms around each set, so two haploid (n) nuclei form.
II
Meiosis II
Metaphase II:
Anaphase II:
Telophase I:
Prophase II:
the chromosomes are aligned midway between spindle poles. Spindle microtubules have attached theis sister chromatids to opposite spindle poles.
The chromosomes condense. Spindle microtubules attach to each sister chromatid as the nuclear envelope breaks up.
Sister chromatids separate and move toward opposite spindle poles. When sister chromosomes separete, each becomes an individual chromosome.
A complete set of chromosomes clusters at each spindle pole. A nuclear envelope forms around each set, so four haploid (n) nuclei form.
Crossing over
Mitosis vs Meiosis
Formative activity: Meiosis flipbook
Thanks
Adapted from: HHMI (n.d.) The Eukaryotic cell cycle and Cancer. Biointeracitve. https://media.hhmi.org/biointeractive/click/cellcycle/ by Xanat Vaitiare Ferreyro Davis