Podcast
Questions and Answers
What is the primary function of the S phase in the cell cycle?
What is the primary function of the S phase in the cell cycle?
Which phase comes right after the G1 phase in interphase?
Which phase comes right after the G1 phase in interphase?
What best describes the activities taking place during the G2 phase?
What best describes the activities taking place during the G2 phase?
During which phase of mitosis do chromosomes align at the cell's equatorial plane?
During which phase of mitosis do chromosomes align at the cell's equatorial plane?
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Which phase is characterized by the condensation of chromatin into visible chromosomes?
Which phase is characterized by the condensation of chromatin into visible chromosomes?
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What is one primary purpose of cell division?
What is one primary purpose of cell division?
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During which phase of the cell cycle does DNA duplication occur?
During which phase of the cell cycle does DNA duplication occur?
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What are the two main stages of cell division in eukaryotes?
What are the two main stages of cell division in eukaryotes?
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Which phase of mitosis involves the alignment of chromosomes at the cell's equatorial plane?
Which phase of mitosis involves the alignment of chromosomes at the cell's equatorial plane?
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What critical function do cell cycle checkpoints serve?
What critical function do cell cycle checkpoints serve?
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During which phase do sister chromatids separate and move to opposite poles of the cell?
During which phase do sister chromatids separate and move to opposite poles of the cell?
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What term describes the overall total DNA unique to a species?
What term describes the overall total DNA unique to a species?
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Which phase follows mitosis to create two separate cells?
Which phase follows mitosis to create two separate cells?
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What is the purpose of the G2 checkpoint in the cell cycle?
What is the purpose of the G2 checkpoint in the cell cycle?
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What happens if a cell does not meet the criteria at the G1 checkpoint?
What happens if a cell does not meet the criteria at the G1 checkpoint?
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Which of the following is checked during the metaphase checkpoint?
Which of the following is checked during the metaphase checkpoint?
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What is the primary difference between mitosis and meiosis regarding the outcome of daughter cells?
What is the primary difference between mitosis and meiosis regarding the outcome of daughter cells?
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How many divisions occur during meiosis?
How many divisions occur during meiosis?
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What consequence does the cell face if errors are detected during the G2 checkpoint?
What consequence does the cell face if errors are detected during the G2 checkpoint?
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What type of reproduction is mitosis primarily associated with?
What type of reproduction is mitosis primarily associated with?
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Which statement accurately describes the chromosome status after meiosis compared to the parent cell?
Which statement accurately describes the chromosome status after meiosis compared to the parent cell?
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What should be included on the front page of your output?
What should be included on the front page of your output?
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In what color should the main text of your output be written?
In what color should the main text of your output be written?
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Which of the following is NOT mentioned as a guideline for word-processed outputs?
Which of the following is NOT mentioned as a guideline for word-processed outputs?
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What should you do if there are unavoidable erasures in your homework?
What should you do if there are unavoidable erasures in your homework?
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Which of the following activities is NOT listed as an asynchronous activity?
Which of the following activities is NOT listed as an asynchronous activity?
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What is the main reason for keeping outputs neat and organized?
What is the main reason for keeping outputs neat and organized?
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What should be done to maintain clarity between activities in your notebook?
What should be done to maintain clarity between activities in your notebook?
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Which font styles are acceptable for word-processed outputs?
Which font styles are acceptable for word-processed outputs?
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Study Notes
Meiosis
- Meiosis is a type of cell division
- It's used in general biology 1
- Prepared by Vender Saddul, LPt, MMin
- The lecture is based on textbook chapter 4, pages 102-127
Agenda for Today
- Routine
- Review of previous lessons
- Motivations
- Teacher-led discussion
- Group activity
- Values integration
- Reminders
Why do cells divide?
-
Ensuring persistence of genome:
- Precisely replicates DNA
- Equally distributes DNA to opposite ends of the cell
- Separates into two identical daughter cells
- Genome = total DNA endowment unique to each species
-
Strategy to counteract loss of SA:Vol ratio as cell grows larger:
- As cells get bigger, their surface area to volume ratio decreases.
- Smaller ratio makes it harder to take in nutrients and get rid of waste products efficiently causing cell division rather than growth.
Why do they have to be so small?
- Surface area to volume ratio
- Too much volume; too little space for diffusion (exchange of substances)
- Diffusion happens at the same rate but in a smaller volume there is less distance to travel
Why do cells divide?
- For growth, development, and repair
- Cells divide to create new cells to grow tissues or organs and to repair already damaged ones.
Cell division in eukaryotes
- Chromosomes consist of DNA and proteins (chromatin)
- Histones help organize/coil DNA
- Mitosis duplicates chromosomes into pairs of sister chromatids:
- Duplication is extremely precise (only 1 error in 100,000)
- Separates the duplicated chromosomes to opposite sides of the cell
- Mitosis is followed by cytokinesis (cytoplasm division)
The cell cycle
- 90% of time spent in interphase
- Interphase consists of:
- G1 phase (first growth phase)
- S phase (DNA duplication)
- G2 phase (second growth phase)
- 10% of time spent in mitosis (M-phase)
- Mitosis: division of the nucleus
- Cytokinesis: division of the cytoplasm
Chromosome Structure
- Chromatin fibres are made up of DNA and histones
- Chromosomes are organized structures made of coiled chromatin
- Chromatids are two identical copies of a chromosome held together by a centromere.
4 Phases of Mitosis
- Mitosis involves 5 phases
- In each phase, specific proteins perform specific roles to divide the genetic material into two daughter cells.
- Cytokinesis follows mitosis
- Prophase, Metaphase, Anaphase, and Telophase
Mitosis in an Onion Root Tip
- Shows the different phases of mitosis under a microscope.
- Illustrations show interphase, prophase, metaphase, anaphase, and telophase.
Cytokinesis
- Processes of dividing the cytoplasm in both animal and plant cells
- Animal cells: cleavage furrow/contractile ring
- Plant cells: cell plate
Cell Cycle Checkpoints
- Ensure each phase is accurately completed before moving to the next step.
- Checkpoints check for various factors such as cell size, DNA replication, DNA damage, nutrients and growth factors.
- Failures in the checkpoints can lead to diseases like cancer
The G1 Checkpoint
- Checks for cell size, nutrient availability, growth factors (signals from other cells) and DNA damage
- If criteria aren't met, cell enters a resting state (G0) or undergoes repair
The G2 Checkpoint
- Ensures the cell is ready to divide (enter mitosis)
- Checks for cell size, complete DNA replication and DNA integrity
The Metaphase Checkpoint
- Ensures proper chromosome alignment and attachment to the mitotic spindle
- Checks for proper attachment of chromosomes to spindle fibres and correct alignment at the metaphase plate.
- If issues arise, the cell pauses to address them, so there's no uneven distribution of chromosomes.
How is Meiosis different from Mitosis?
- Mitosis: Cell division for growth, repair and asexual reproduction. Produces two identical diploid daughter cells. Chromosome copy number remains same. Doesn't cause genetic variations
- Meiosis: Cell division for sexual reproduction. Produces four genetically unique haploid daughter cells. Chromosome number is halved. Causes genetic variations
Number of Divisions
- Mitosis: Involves one division, producing two daughter cells
- Meiosis: Involves two divisions, producing four daughter cells
Daughter Cells
- Mitosis: Results in two genetically identical diploid cells (same number of chromosomes as the parent cell)
- Meiosis: Results in four genetically unique haploid cells (half the number of chromosomes of the parent cell)
Cell Cycle Summary
- Mitosis and Meiosis are different types of cell division, each with distinct processes, purposes, and outcomes. Mitosis is for growth and repair, while Meiosis is for sexual reproduction.
Meiosis Videos
- YouTube videos on Meiosis
Cell Division Videos
- YouTube videos on cell division.
- Links to online resources are included for cellular division videos and animations.
Homework
- Create a table comparing mitosis and meiosis. The table should cover the purpose, number of chromosomes involved, genetic variation, number of divisions, and daughter cells.
- Mark the start of the second quarter in your notebook.
Submission of Outputs
- Formatting guidelines for assignments (titles, subtitles, fonts, indentations, page numbering).
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Description
Explore the fascinating process of meiosis, a crucial type of cell division that ensures genetic persistence and optimal cell size. This quiz is based on Chapter 4 of the general biology textbook and delves into key concepts such as DNA replication and the surface area to volume ratio. Test your knowledge and understanding of why cells divide and the importance of maintaining genome integrity.
