Questions and Answers
What does 'homologous' refer to?
What does 'diploid' mean?
Two sets of chromosomes
What are other names for diploid?
Body cells, somatic
What does 'haploid' refer to?
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What are other names for haploid?
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What is meiosis?
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Meiosis is ______ to ______ (haploid, diploid)
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What is a tetrad?
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What is a chromatid?
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What is crossing-over?
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What is a zygote?
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How many sets of genes are found in most adult organisms?
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What does '2N' represent?
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What does 'N' represent?
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What events occur during prophase I?
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What events occur during metaphase I?
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What events occur during anaphase I?
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What happens in telophase I/cytokinesis?
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What occurs during prophase II?
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What occurs during metaphase II?
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What occurs during anaphase II?
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What occurs during telophase II?
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What happens during cytokinesis after telophase II?
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How is meiosis different from mitosis?
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What is the purpose of meiosis?
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What kind of cell does meiosis start with and end with?
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How many cells does meiosis start with and end with?
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Where does meiosis happen in the body?
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How do the cells made compare to the original cell?
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What are some similarities between mitosis and meiosis?
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What are the differences between mitosis and meiosis?
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How many usable cells are created in meiosis for males and females?
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What are the names of the cells created in males and females?
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When does meiosis happen for males?
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When does meiosis happen for females?
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Why is there a difference between males' and females' meiosis?
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Haploid cells are _____ cells/gametes.
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Diploid cells are _____ cells/somatic.
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What process makes diploid cells?
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What process makes haploid cells?
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What does it mean to be a homologous pair of chromosomes?
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The chromosomes in a homologous pair are similar but not identical-what's the same? What's different?
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What makes up a tetrad?
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When do tetrads form?
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What do tetrads have to do with homologous pairs of chromosomes?
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The word tetrad comes from the root 'tetra' meaning 'four'; what does the 4 have to do with tetrads?
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What is the benefit of crossing over?
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When does crossing over occur?
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Study Notes
Key Terms and Definitions
- Homologous: Sets of chromosomes where each chromosome from one parent corresponds to one from the other parent.
- Diploid: Cells containing two sets of homologous chromosomes; also referred to as body cells or somatic cells.
- Haploid: Cells with one set of chromosomes, known as sex cells or gametes.
- Meiosis: Cell division process reducing the chromosome number by half, producing haploid cells from diploid cells.
- Zygote: The fertilized egg resulting from the fusion of sperm and egg cells.
Meiosis Process
- Begins with a diploid cell and results in four haploid cells.
- Consists of two rounds of division: Meiosis I and Meiosis II, separating homologous chromosomes and then sister chromatids.
Key Stages of Meiosis
- Prophase I: Homologous chromosomes pair up, forming tetrads; crossing over occurs.
- Metaphase I: Homologous pairs line up at the cell equator, spindle fibers attach to centromeres.
- Anaphase I: Spindle fibers pull homologous chromosomes to opposite poles of the cell.
- Telophase I/Cytokinesis: Nuclear membranes form around each cluster of chromosomes; two new cells are created.
- Prophase II: Chromosomes become visible again; centrioles replicate.
- Metaphase II: Sister chromatids align along the equator; centromeres attach to spindle fibers.
- Anaphase II: Sister chromatids are pulled apart to opposite poles.
- Telophase II: Nuclear membranes reform, resulting in the division of the cytoplasm and yielding four haploid daughter cells.
Genetic Outcomes and Comparisons
- Meiosis increases genetic variation through processes like crossing over.
- Mitosis produces two genetically identical diploid cells; meiosis produces four genetically different haploid cells.
- Male meiosis results in four usable sperm cells, while female meiosis typically results in one usable egg cell due to unequal cytokinesis.
Differences Between Mitosis and Meiosis
- Meiosis occurs in sex cells for reproduction while mitosis occurs in body cells for growth and repair.
- Meiosis includes two divisions and results in haploid cells, while mitosis results in diploid cells.
Tetrads and Crossing Over
- Tetrads consist of two homologous chromosomes, each with two sister chromatids, forming during prophase I.
- Crossing over occurs during prophase I, contributing to genetic diversity by exchanging segments between homologous chromosomes.
Additional Facts
- Diploid chromosome number is represented as 2N, while haploid as N.
- Meiosis occurs in reproductive organs, necessary for gamete formation.
- The difference in meiotic processes between males and females is driven by reproductive strategies: males produce continuously, whereas females have a finite number of eggs.
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Test your understanding of key terms related to meiosis with these flashcards. Each card includes a terminology definition that will help solidify your knowledge on concepts such as homologous chromosomes and diploid cells.