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Questions and Answers
During which phase does chromosome replication occur?
During which phase does chromosome replication occur?
What are the duplicated copies of a chromosome called?
What are the duplicated copies of a chromosome called?
What important structures synthesize during the G2 phase of Interphase?
What important structures synthesize during the G2 phase of Interphase?
Which of the following describes the state of genetic material during interphase?
Which of the following describes the state of genetic material during interphase?
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What happens to organelles and proteins during interphase?
What happens to organelles and proteins during interphase?
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What structures are eukaryotic chromosomes composed of?
What structures are eukaryotic chromosomes composed of?
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During cell division, how do chromosomes become visible under a microscope?
During cell division, how do chromosomes become visible under a microscope?
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How many chromosomes do human body cells typically have?
How many chromosomes do human body cells typically have?
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What type of chromosomes are found in all eukaryotic cells?
What type of chromosomes are found in all eukaryotic cells?
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What is the relationship between homologous chromosomes?
What is the relationship between homologous chromosomes?
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What is the result of fertilization in terms of ploidy level?
What is the result of fertilization in terms of ploidy level?
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What is the main purpose of meiosis in sexual reproduction?
What is the main purpose of meiosis in sexual reproduction?
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Which statement about gametes is true?
Which statement about gametes is true?
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What happens to the chromosome number after fertilization takes place?
What happens to the chromosome number after fertilization takes place?
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How many chromosomes are found in each haploid gamete if a diploid organism has 6 chromosomes?
How many chromosomes are found in each haploid gamete if a diploid organism has 6 chromosomes?
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What occurs during Anaphase II of meiosis?
What occurs during Anaphase II of meiosis?
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What is the main event that occurs during Telophase II?
What is the main event that occurs during Telophase II?
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What is the role of the spindle during Anaphase II?
What is the role of the spindle during Anaphase II?
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What happens to the chromosomes during Telophase II?
What happens to the chromosomes during Telophase II?
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Cytokinesis in Telophase II primarily results in what?
Cytokinesis in Telophase II primarily results in what?
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What is the main outcome of Meiosis I?
What is the main outcome of Meiosis I?
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During which phase of Meiosis I does crossing over occur?
During which phase of Meiosis I does crossing over occur?
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What distinguishes Meiosis II from Meiosis I?
What distinguishes Meiosis II from Meiosis I?
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What happens in the late prophase stage of Meiosis I?
What happens in the late prophase stage of Meiosis I?
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The term 'haploid' refers to cells that contain how many sets of chromosomes?
The term 'haploid' refers to cells that contain how many sets of chromosomes?
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What is the role of spindle fibers during Meiosis?
What is the role of spindle fibers during Meiosis?
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At the end of Meiosis I, how many cells are produced?
At the end of Meiosis I, how many cells are produced?
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Which process contributes directly to genetic variation during meiosis?
Which process contributes directly to genetic variation during meiosis?
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What is the primary purpose of mitosis?
What is the primary purpose of mitosis?
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Which stage of mitosis involves the alignment of chromosomes along the equatorial plane?
Which stage of mitosis involves the alignment of chromosomes along the equatorial plane?
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How many stages are there in mitosis?
How many stages are there in mitosis?
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Which of the following cells does not normally undergo mitosis?
Which of the following cells does not normally undergo mitosis?
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During which phase do the sister chromatids separate and move towards opposite poles of the cell?
During which phase do the sister chromatids separate and move towards opposite poles of the cell?
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What structure in the cell helps in the movement of chromosomes during mitosis?
What structure in the cell helps in the movement of chromosomes during mitosis?
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Which phase of mitosis is characterized by the breakdown of the nuclear envelope?
Which phase of mitosis is characterized by the breakdown of the nuclear envelope?
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What is the result of mitosis?
What is the result of mitosis?
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What happens to chromatin during prophase?
What happens to chromatin during prophase?
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In mitosis, what is formed when the cell completes the telophase?
In mitosis, what is formed when the cell completes the telophase?
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Study Notes
Cell Cycle and Division
- Cells originate from pre-existing cells
- New cells are produced for growth and replacement of damaged or old cells
- Cell division differs in prokaryotes (bacteria) and eukaryotes (protists, fungi, plants, and animals)
DNA Replication
- DNA must be copied before cell division
- Each new cell receives a complete copy of the DNA
Identical Daughter Cells
- Daughter cells contain the same number of chromosomes as the parent cell.
- They are identical to each other but smaller.
- They grow in size in G1 of Interphase to become mature cells.
Chromosomes
- DNA is packaged tightly into structures called chromosomes
- Long thread-like shapes made of DNA and protein, which coil up tightly into X shapes during cell division, becoming visible under a microscope.
- Chromosomes in eukaryotic cells are diploid (2n) and contain 23 pairs of homologous chromosomes, for a total of 46.
Chromosome Definitions
- Homologous chromosomes are the same size and shape and carry the same types of genes in the same order.
- Diploid (2n) refers to a cell containing two sets of homologous chromosomes.
- Haploid (n) refers to a cell containing one set of chromosomes.
Sets of Human Chromosomes
- The first 22 pairs of chromosomes in a human cell are called autosomes.
- The 23rd pair (XX or XY) are the sex chromosomes.
The Cell Cycle
- The series of events from the time a cell forms until it divides is called the cell cycle.
- It is divided into two major phases: Interphase and Mitosis (M phase).
Interphase
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Interphase is the first major phase of the cell cycle
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Includes G1 (Gap 1), S (Synthesis), and G2 (Gap 2) phases.
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G1 (Gap 1)
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1st growth stage after cell division
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Cells mature by making more cytoplasm and organelles
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Cell carries out normal metabolic activities
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S (Synthesis)
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DNA is copied or replicated
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Each chromosome replicates to form sister chromatids
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Sister chromatids are attached at the centromere
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G2 (Gap 2)
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2nd growth stage after DNA replication
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All cell structures needed for cell division are made
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e.g., centrioles
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Organelles and proteins are synthesized
DNA Replication in Chromosomes
- Cells replicate their DNA during Interphase's S phase.
- Each duplicated chromosome has two sister chromatids joined at the centromere.
Mitosis
- Mitosis is a process that divides the nucleus of a cell.
- It has four stages: Prophase, Metaphase, Anaphase, and Telophase
- The cell divides into two identical copies
Prophase
- Chromatin in nucleus condenses to form visible chromosomes; Each chromosome is composed of two sister chromatids joined at the centromere.
- Centrioles move to opposite sides of nucleus; Spindle microtubules appear in the cytoplasm; Nuclear envelope and nucleolus disassemble.
Metaphase
- Chromosomes, attached to kinetochore fibers, move to the center of the cell; Chromosomes line up at the equator of the cell.
Anaphase
- Sister chromatids are pulled apart to opposite poles of the cell by kinetochore fibers; Centromeres split separating sister chromatids.
Telophase
- Sister Chromatids are at opposite poles; Spindle disassembles; Nuclear envelope forms around each set of sister chromatids; Nucleolus reappears; Chromosomes reappear as chromatin; Cytokinesis occurs.
Cytokinesis
- Cytoplasm divides, creating two identical daughter cells.
Meiosis
- Meiosis is a type of cell division that produces gametes (eggs and sperm).
- The process of meiosis involves two meiotic divisions.
- The original cell is diploid (2n), but the resulting gametes are haploid (n).
- This halving of chromosomes is essential for sexual reproduction.
Meiosis I: Reduction Division
- Early Prophase I: Homologs pair and crossing over occurs
- Late Prophase I: Chromosomes condense, spindle forms, and nuclear envelope breaks down.
- Metaphase I: Homologous pairs align along the cell's equator.
- Anaphase I: Homologous chromosomes separate and move to opposite poles, while sister chromatids remain attached.
- Telophase I: Nuclear envelopes reform, and cytokinesis occurs, producing two haploid cells.
Meiosis II
- Prophase II: Chromosomes condense, and spindle apparatus forms again.
- Metaphase II: Chromosomes align along the cell's equator.
- Anaphase II: Sister chromatids separate and move to opposite poles.
- Telophase II: Nuclear envelopes reform, spindle disappears, and cytokinesis occurs, resulting in four haploid daughter cells.
Crossing-Over
- During Prophase I, homologous chromosomes exchange pieces of chromosome or genes
- Results in genetic recombination in offspring.
Results of Meiosis
- Produces gametes (eggs and sperm)
- Four haploid cells with one copy of each chromosome, with different combinations of alleles for different genes.
Spermatogenesis
- Production of sperm in males, involving mitosis and meiosis to generate haploid sperm cells.
Oogenesis
- Production of eggs in females, involving mitosis and meiosis to create a single mature egg and polar body cells.
Mitosis vs. Meiosis
- Key Differences:
- Mitosis: One division, identical daughter cells, used for growth and repair.
- Meiosis: Two divisions, unique daughter cells, used for sexual reproduction.
Fertilization
- The fusion of a haploid egg and a haploid sperm to form a diploid zygote.
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Description
Test your knowledge on cell division and the genetic processes during interphase and meiosis. This quiz covers essential concepts such as chromosome replication, homologous chromosomes, and the role of gametes in sexual reproduction. Challenge yourself and see how well you understand these fundamental biological processes.
