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What is the main purpose of the cell cycle?
What is the main purpose of the cell cycle?
Somatic cells contain a haploid (n) number of chromosomes.
Somatic cells contain a haploid (n) number of chromosomes.
False
What stage precedes mitosis in the cell cycle?
What stage precedes mitosis in the cell cycle?
Interphase
A sperm cell is an example of a __________ cell.
A sperm cell is an example of a __________ cell.
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Match the following phases with their descriptions:
Match the following phases with their descriptions:
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Which type of chromosomes are involved in determining the sex of an individual?
Which type of chromosomes are involved in determining the sex of an individual?
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The G2 phase involves the replication of DNA.
The G2 phase involves the replication of DNA.
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During which phase of interphase does the cell synthesize new proteins?
During which phase of interphase does the cell synthesize new proteins?
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What is the primary purpose of mitosis?
What is the primary purpose of mitosis?
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Mitosis results in four daughter cells with half the chromosome number of the parent cell.
Mitosis results in four daughter cells with half the chromosome number of the parent cell.
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During which phase of mitosis does the nuclear membrane disappear?
During which phase of mitosis does the nuclear membrane disappear?
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Mitosis is also known as __________ division.
Mitosis is also known as __________ division.
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Match the stages of meiosis with their descriptions:
Match the stages of meiosis with their descriptions:
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What occurs during anaphase of mitosis?
What occurs during anaphase of mitosis?
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Cytokinesis results in the formation of two daughter cells in both mitosis and meiosis.
Cytokinesis results in the formation of two daughter cells in both mitosis and meiosis.
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What are the two types of cell division discussed?
What are the two types of cell division discussed?
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What is the primary purpose of crossing over during pachytene?
What is the primary purpose of crossing over during pachytene?
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Spermatogenesis produces four mature spermatids from one precursor cell.
Spermatogenesis produces four mature spermatids from one precursor cell.
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What is formed at the end of meiosis II?
What is formed at the end of meiosis II?
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During __________, homologous chromosomes align along the cell's equator.
During __________, homologous chromosomes align along the cell's equator.
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Match the phase of meiosis with its correct description:
Match the phase of meiosis with its correct description:
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What structures develop from the process of oogenesis?
What structures develop from the process of oogenesis?
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Cytokinesis during meiosis results in two diploid daughter cells.
Cytokinesis during meiosis results in two diploid daughter cells.
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Where does spermatogenesis occur in the male body?
Where does spermatogenesis occur in the male body?
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How many daughter cells are produced after mitosis?
How many daughter cells are produced after mitosis?
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There are 40 kinetochores present during anaphase.
There are 40 kinetochores present during anaphase.
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How many homologous chromosomes are present during metaphase 1?
How many homologous chromosomes are present during metaphase 1?
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After meiosis II, a sex cell has _ chromatids.
After meiosis II, a sex cell has _ chromatids.
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Match the following phases with their corresponding chromatid count:
Match the following phases with their corresponding chromatid count:
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What is the primary function of meiosis in the ovaries?
What is the primary function of meiosis in the ovaries?
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Polar bodies produced during oogenesis survive and contribute to fertilization.
Polar bodies produced during oogenesis survive and contribute to fertilization.
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What is the term for the immature egg in the ovaries?
What is the term for the immature egg in the ovaries?
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After mitosis, a parent cell with 20 chromosomes will have _____ chromosomes in each daughter cell.
After mitosis, a parent cell with 20 chromosomes will have _____ chromosomes in each daughter cell.
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How many polar bodies are produced during oogenesis?
How many polar bodies are produced during oogenesis?
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How many chromosomes are present in each daughter cell after meiosis if the parent cell has 20 chromosomes?
How many chromosomes are present in each daughter cell after meiosis if the parent cell has 20 chromosomes?
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Starting at puberty, one oocyte matures into an _____ every 28 days.
Starting at puberty, one oocyte matures into an _____ every 28 days.
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Match the following terms with their definitions:
Match the following terms with their definitions:
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Study Notes
Cell Cycle
- The cell cycle is a series of events that cells go through during growth and division.
- During the cell cycle, the cell grows, prepares for division, and divides to form two daughter cells.
- Each daughter cell begins the cell cycle again.
Cell Division
-
Somatic cells are all body cells except sex cells.
- Contain diploid (2n) number of chromosomes.
- Have 46 chromosomes, or 23 pairs.
- Undergo mitosis.
-
Sex cells/Reproductive cells/Gametes/Germ cells:
- Ovum/ova are produced from the female reproductive organ.
- Spermatozoa are produced from the male reproductive organ.
- Contain 23 chromosomes (1 set).
- Are haploid (n), containing half of the original number of chromosomes.
- The 22nd pair of chromosomes are called autosomes, and the 23rd pair are called sex chromosomes.
-
Homologous chromosomes:
- Have the same length.
- Have the same position of the centromere.
- Have the same genes, but not necessarily the same alleles.
Types of Chromosomes
- Telocentric: Centromere is at the end.
- Acrocentric: Centromere is near the end.
- Submetacentric: Centromere is between the center and the end.
- Metacentric: Centromere is at the center.
Interphase
- The preparatory stage for mitosis.
- The nucleus is clearly visible, with a distinct nucleolus.
- Chromosomes appear as irregular granular forms and cannot be recognized.
- Consists of three subdivisions:
- G1 (first growth period): The cell grows in size, synthesizes new proteins, and prepares chromosomes for replication.
- S (synthesis period): DNA synthesis and replication takes place, RNA and protein synthesis continue, and centriole replication begins.
- G2 (second growth period): DNA synthesis and replication are completed, chromatids duplicate, and the cell prepares to undergo mitosis.
Mitosis
- A process that produces two daughter cells with the same quantity and quality of chromosomes as the parent cell (identical).
- Also known as duplication division.
- Used for growth and repair of body cells.
- Each cell receives diploid (2n) number of chromosomes.
Stages of Mitosis
-
Prophase:
- Chromosomes start to coil and become visible.
- The nucleolus is no longer visible.
- The nuclear membrane starts to disappear.
- Centrioles move to opposite poles of the cell due to formation of spindle fibers.
-
Metaphase:
- Double-stranded chromosomes are aligned at the equator of the cell.
- Kinetochores of each chromosome are attached to spindle fibers.
- The nuclear membrane completely disappears.
-
Anaphase:
- Continued contraction of spindle fibers separates sister chromatids.
- Chromatids move to opposite poles of the cell (migration phase).
- Cytokinesis begins (formation of cell plate in plants and cleavage furrow in animals).
-
Telophase:
- Chromatids arrive at opposite poles.
- Chromatids start to uncoil.
- The nucleolus reappears.
- Spindle fibers disappear.
- A new nuclear membrane forms.
- Cytokinesis is completed, resulting in two daughter cells with the same quantity and quality of chromosomes as the parent cell.
Meiosis
- Also known as reduction division.
- Produces 4 haploid (n) daughter cells.
- Occurs in germ cells to produce gametes.
- Involves two successive divisions: Meiosis I and Meiosis II.
Why Meiosis is Important
- Ensures variation in the daughter cells.
Stages of Meiosis I
-
Prophase I: The longest duration of meiosis. It is further divided into five substages:
- Leptotene: Chromosomes become more visible than in interphase.
- Zygotene: Homologous chromosomes pair off (synapsis). The pair is referred to as a bivalent or tetrad.
- Pachytene: Exchanging/transferring of genetic material between chromatids (crossing over). The site of crossing over is called a chiasma. This ensures that the daughter cells contain genes from both parents.
- Diplotene: The synaptonemal complex dissolves, leaving recombinant chromosomes.
- Diakinesis: The nuclear envelope and nucleolus disintegrate. Centrioles move to opposite poles. Spindle fibers begin to form.
- Metaphase I: Homologous pairs of chromosomes align along the equator of the cell.
- Anaphase I: Homologs separate and move to opposite poles. Sister chromatids remain attached at their centromeres.
- Telophase I: Nuclear envelopes reassemble, the spindle disappears, and cytokinesis divides the cell into two.
Stages of Meiosis II
- Prophase II: The nuclear envelope fragments, spindle fibers form, and centrioles move to opposite poles. Chromosomes are more visible.
- Metaphase II: Chromosomes align along the equator of the cell.
- Anaphase II: Sister chromatids separate and move to opposite poles.
- Telophase II: Nuclear envelopes assemble, chromosomes uncoil, the spindle disappears, and cytokinesis divides the cell into two. Cytokinesis results in 4 haploid (n) daughter cells with unduplicated chromosomes.
Results of Meiosis
- Gametes (egg & sperm) are formed.
- Four haploid cells with one copy of each chromosome are created.
- Each cell has one allele of each gene.
- There are different combinations of alleles for different genes along the chromosome.
Gametogenesis
- Spermatogenesis: The creation of sperm cells. Two divisions produce 4 spermatids. Spermatids mature into sperm. Occurs in the testes. Men produce about 250,000,000 sperm per day.
- Oogenesis: The creation of egg cells. It occurs in the ovaries. Two divisions produce 3 polar bodies that die and 1 egg. Polar bodies die due to unequal division of cytoplasm. An immature egg is called an oocyte. Starting at puberty, one oocyte matures into an ovum (egg) every 28 days.
Comparison of Mitosis and Meiosis
| Feature | Mitosis | Meiosis |
|---|---|---|
| Number of Divisions | 1 | 2 |
| Number of Daughter Cells | 2 diploid cells | 4 haploid cells |
| Genetically | Identical | Different |
| Chromosome # | Same as parent | Half of parent |
| Where | Somatic cells | Germ cells |
| When | Throughout life | At sexual maturity |
| Function | Growth and repair | Sexual reproduction |
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Description
Explore the fascinating processes of the cell cycle and cell division in this quiz. Learn about somatic and sex cells, their chromosome numbers, and how they replicate and divide. Test your understanding of mitosis, meiosis, and the different types of chromosomes.
