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Related Flashcards
Cards In This Set
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How many chromosomes does a fruit fly (Drosophila) have?
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8
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4 of the chromosomes came from the male parent and the 4came from its female parent, these two sets of chromosomes are _______, meaning that each of the 4 chromosomes that came from the male parent has a corrsponding chromosome from the female parent.
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Homologous (they have a similar structure and genetic function)
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A cell that contains both sets of homologous chromosomes is said to be _____, which means "two sets."
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Diploid
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The number of chromosomes in a diploid cell is sometimes represented by the symbol 2N. Thus for the fruit fly, the diploid number is 8, which can be written as ______.
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2N = 8
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Diploid cells contain two complete sets of chromosomes and two complete sets of ____. This agrees with Mendel's idea that the cell of an adult organism contain two copies of each ____.
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Genes; gene
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The gametes of sexually reproducing organisms contain only a single set of ____, and therefore only a single set of ____. Such cells are said to be _____, which means "one set." For a fruit fly, this can be written as ______.
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Chromosomes; genes; haploid; N=4
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During meiosis, the number of chromosomes per cell is cut in half through the separation of the _____ chromosomes. The result of meiosis is _________ that are genetically different from one another and from the original cell.
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Homologous; 4 haploid cells
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What happens in Interphase I?
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Cells undergo a roud of DNA replication, forming duplicate chromosomes.
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What happens in Prophase I?
What happens in Metaphase I?
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PROPHASE I: Each chromosome pairs with its corresponding homologous chromosome to form a tetrad (there are 4 chromosomes in this).
METAPHASE I: Spindle fibers attach to chromosomes, chromosomes line up
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What happens in Anaphase I?
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The fibers pull the homologous chromosomes toward opposite ends of the cell.
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What happens in Telophase I and Cytokinesis?
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the nuclear membrane forms and the cell separates into two new haploid daughter cells.
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When does crossing-over occur? What is it?
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As homologous chromosomes pair up and form tetrads in Meiosis I, they exchange portions of their chromatids in a process called crossing-over.
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What does crossing-over result in? what does it produce? Where is the material exchanged?
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Results in the exchange of alleles between homologous chromosomes and produces new combinations of alleles. Exchange of material between NON - sister chromatids.
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Why is the results of Meiosis I different than mitosis when the number of chromatids is the same?
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Because each pair of homologous chromosomes was separated, neither of the daughter cells has the two complete sets of chromosomes that it would have in a diploid cell.
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Is there replication prior it Meiosis II?
What is the result of Meiosis I? (nothing really happens in Prophase II... except the nuclear membrane disappears)
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NO; Meiosis I results in two haploid (N) daughter cells, each with half the number of chromosomes as the original cell.
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