Lesson 34-36 Variation in Chromosome Structure and Number.ppt

Lesson 34-36 Variation in Chromosome Structure and Number.ppt

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Unformatted text preview: BIO 325 Genetics Lectures 34, 35, and 36 Variation in Chromosome Structure and Number "Sir, if you were my husband, I would poison your drink." -- Lady Astor to Winston Churchill "Madam, if you were my wife, I would drink it." -- His reply Genetic variation refers to genetic differences among members of the same species or genetic differences between different species. Variation in Chromosome Structure and Number Genetic variation refers to genetic differences among members of the same species or genetic differences between different species. Allelic variation refers to variation within a specific gene. Variation in Chromosome Structure and Number Natural variation exists in chromosome structure. The chromosomes for a given species vary in both size and shape. Variation in Chromosome Structure Chromosomes are named according to the location of their centromere. Based on the location of the centromere, the chromosome is called metacentric, submetacentric, acrocentric, or telocentric. All chromosomes have a long and short arm. Variation in Chromosome Structure Chromosomes are named according to the location of their centromere. Based on the location of the centromere, the chromosome is called metacentric, submetacentric, acrocentric, or telocentric. All chromosomes have a long and short arm. The long arm of the chromosome is called q , and the short arm of the chromosome is called p . Variation in Chromosome Structure A karyotype is a micrograph that arranges the chromosomes with the short arm at the top, and then in descending order by size. Variation in Chromosome Structure Variation in Chromosome Structure Cytogeneticists, scientists who study chromosomes microscopically, may use stains to further identify chromosomes. The use of Giemsa stain produces a G banding pattern, which is used as a standard identification pattern for chromosomes. Banding patterns may also be used to identify changes in chromosome structure. Changes in chromosome structure include deletions, duplications, inversions, and translocations. Variation in Chromosome Structure Changes in chromosome structure may either change the amount of genetic material within the chromosome (increase or decrease) or rearrange the genetic material within a chromosome or between two chromosomes. Variation in Chromosome Structure Deletions decrease the genetic content of the chromosome; duplications increase the genetic content of the chromosome; inversions change the arrangement of the chromosome; Translocations typically change both the arrangement of the chromosome and the genetic content. Variation in Chromosome Structure Translocations may be either simple translocations (a single piece of a chromosome is attached to another chromosome) or reciprocal translocations (two different chromosomes exchange pieces....
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Lesson 34-36 Variation in Chromosome Structure and Number.ppt

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