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40 Cards in this Set
- Front
- Back
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Exercise 9
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Cell Division in Eukaryotes
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Two types of nuclear division in eukaryotes
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Mitosis and Meiosis
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Mitosis
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A process of nuclear division in eukaryotic cells conventionally divided into five stages: phophase, prometaphase, metaphase, anaphase, and telophase. Mitosis conserves chromosome number by allocating replicated chromosomes equally to each of the daughter nuclei.
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Meiosis
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A modified type of cell division in sexually reproducing organisms consisting of two rounds of cell division but only one round of DNA replication. It results in cells with half the number of chromosome sets as the original cell.
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Interphase
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Many of the cells will be in this non-dividing portion of the cell cycle. The nucleus, nucleoli, and nuclear envelope are still intact and chromosomes are not visible.
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Mitotic Phase
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The phase of the cell cycle that includes mitosis and cytokinesis.
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Prophase
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In this first stage of mitosis, the nuclear material condenses into chromosomes (each consisting of two sister chromatids connected at the centromere), and the nuclear membrane breaks down. The nuclear area will appear dark and heavily grainy or stringy. Spindle fibers develop.
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Metaphase
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In this stage, the chromosomes are lined up along the middle of the cell, just before separation occurs.
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Anaphase
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In this stage, the sister chromatids (now called chromosomes) have seperated and you can see them move towards opposite ends of the cell.
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Telophase
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In this stage, the chromosomes decondense to form chromatin. Overlapping with telophase is cytokinesis which is defined as the division of the cytoplasm. Cytokinesis is identified by the formation of the cell plate in plants and the cleavage furrow in animals. The cell plate is the beginning of a new plant cell wall that will eventually separate the cell into two daughter cells while the cleavage furrow deepens to eventually pinch the animal cell into two daughter cells.
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Blastula
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A stage in the embryological developement of animals in which cells are rapidly dividing.
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Diploid Cell
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A cell containing two sets of chromosomes (2n), one set inherited from each parent.
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Sister Chromatid
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Either of two copies of a duplicated chromosome attached to each other by proteins at the centromere and, sometimes, along the arms. While joined, two sister chromatids make up one chromosome; chromatids are eventually separated during mitosis or meiosis II.
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Diploid (2n)
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A cell or an organism consisting of two sets of chromosomes: usually, one set from the mother and another set from the father. In a diploid state the haploid number is doubled, thus, this condition is also known as 2n.
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Haploid (1n)
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(1) The number of chromosomes in a gamete or sex cells of an organism, symbolized by n.
(2) A cell or an organism having half of the number of chromosomes in somatic cells. |
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Fertilization
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The union of haploid gametes to produce a diploid zygote.
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Sexual Reproduction
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A type of reproduction in which two parents give rise to offspring that have unique combinations of genes inherited from the gametes of the parents.
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Zygote
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The diploid product of the union of haploid gametes during fertilization; a fertilized egg.
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Meiosis I
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The reductive division - diploid cells divide to produce haploid cells by the separation of homologous chromosomes.
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Meiosis II
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The equatorial division - a mitotic-like division in which sister chromatids could separate.
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Know the names of the plant and animal cells we used to study mitosis.
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Allium (onion) root tip and whitefish blastula
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Know the names of the plant and animal cells we used to study mitosis.
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Allium (onion) root tip and whitefish blastula
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Interphase
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. . . . . |
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Prophase I
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. . . . . |
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Metaphase I
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. . . . . |
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Anaphase I
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. . . . . |
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Telophase I and Cytokinesis
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. . . . . |
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Prophase II
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Metaphase II
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Anaphase II
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Telophase II and Cytokinesis
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. . . . . . |
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Table 9.1
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Table 9.1
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Meiosis
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Mitosis
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Produces gametes or spores
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Produces somatic cells
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Occurs in reproductive organs
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Occurs in cells of all other organs
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Two linked divisions - the reductive division and the equatorial divsion
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Only one division
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Four cells are normally 0produced (some may be lost
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Two cells are produced
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Resulting cells have half the chromosome number of parent cells (haploid, 1n)
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Resulting cells have the same number of chromosomes as the parent cell (diploid, 2n)
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Synapsis of homologous chromosomes occurs
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No synapsis involved
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During synapsis, there is an exchange of genetic material (crossing over) between paired chromosomes. Thus, the gametes are a recombination of the genetic characteristics parent cells.
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The resulting cells are identical to the parent cells in terms of genetic characteristics (excluding mutations).
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