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Questions and Answers
What process contributes to genetic variation by randomly aligning chromosomes along the equator during meiosis?
What process contributes to genetic variation by randomly aligning chromosomes along the equator during meiosis?
- DNA replication
- Crossing over
- Independent assortment (correct)
- Cytokinesis
What occurs during prophase one of meiosis?
What occurs during prophase one of meiosis?
- Centrioles disappear.
- Chromosomes become elongated.
- Crossing over between homologous chromosomes occurs. (correct)
- Chromatids separate.
During meiosis II, crossing over occurs between chromosomes.
During meiosis II, crossing over occurs between chromosomes.
False (B)
What is the resulting genetic composition of gametes after telophase of meiosis II?
What is the resulting genetic composition of gametes after telophase of meiosis II?
Independent assortment occurs during metaphase one of meiosis.
Independent assortment occurs during metaphase one of meiosis.
The nuclear envelope reforms during ______ in meiosis.
The nuclear envelope reforms during ______ in meiosis.
What is the process called when chromosomal sections are exchanged between homologous chromosomes?
What is the process called when chromosomal sections are exchanged between homologous chromosomes?
Match the following phases of meiosis with their descriptions:
Match the following phases of meiosis with their descriptions:
In meiosis one, the DNA content is ______ by half during the reduction division.
In meiosis one, the DNA content is ______ by half during the reduction division.
Match the following stages of meiosis with their descriptions:
Match the following stages of meiosis with their descriptions:
Flashcards
Prophase I
Prophase I
The first stage of meiosis I, during which chromosomes condense, centrioles move to the poles, and spindle fibers form. Crossing over, a crucial process for genetic variation, also occurs in this phase.
Metaphase I
Metaphase I
The homologous pairs of chromosomes line up along the equator of the cell during metaphase I. Spindle fibers attach to the centromeres.
Anaphase I
Anaphase I
Pairs of homologous chromosomes are pulled apart by spindle fibers towards opposite poles of the cell, reducing the number of chromosomes in each daughter cell by half.
Telophase I
Telophase I
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Crossing Over
Crossing Over
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Independent Assortment
Independent Assortment
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Cytokinesis
Cytokinesis
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Study Notes
Meiosis Stages
- Meiosis is a two-stage process: meiosis I and meiosis II.
- Meiosis I is a reduction division, reducing the DNA content by half.
Prophase I
- Chromosomes condense by coiling around histones.
- Centrioles move to cell poles, forming spindle fibers.
- Crossing over: Homologous chromosomes (bivalents) pair up. Maternal and paternal chromosomes exchange genetic information at points called chiasmata. This exchange creates genetic variation.
Metaphase I
- Bivalents align along the cell equator.
- Spindle fibers attach to centromeres.
- Independent assortment: Chromosomes can align in different ways along the equator, leading to genetically unique gametes. This random arrangement creates many possible combinations of chromosomes in the resulting gametes. Human cells have 23 pairs of chromosomes, enabling over 8 million combinations in gametes.
Anaphase I
- Bivalents are pulled apart by contracting spindle fibers, to opposite poles. This halves the genetic information in each cell.
Telophase I
- Chromosomes begin to uncoil.
- Nuclear envelope reforms.
- Cytokinesis begins, pinching off the cell membrane and creating two separate cells.
Meiosis II
- Meiosis II is similar to mitosis.
Prophase II
- Spindle fibers reform.
- Chromosomes condense.
- No crossing over occurs.
Metaphase II
- Chromosomes align along the equator.
- Spindle fibers attach to centromeres.
- Independent assortment happens again.
Anaphase II
- Chromosomes are pulled to opposite poles by contracting spindle fibers.
Telophase II
- Chromosomes uncoil.
- Nuclear envelope reforms.
- Cytokinesis occurs, resulting in four haploid, genetically different gametes.
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