Chapter - 8.ppt-BB - 2012

Division without in drosophila pairs of in drosophila

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Unformatted text preview: ntrast to animals, plants commonly In exhibit polyploidy exhibit In many instances, polyploid strains of In plants display outstanding agricultural characteristics characteristics Polyploids having an odd number of chromosome sets Polyploids are usually sterile are These plants produce highly aneuploid gametes NATURAL AND EXPERIMENTAL WAYS TO PRODUCE VARIATIONS IN CHROMOSOME NUMBER CHROMOSOME There are three natural mechanisms by There which the chromosome number of a species can vary can 1. 1. 2. 3. 3. Meiotic Nondisjunction Meiotic Nondisjunction refers to the failure of chromosomes Nondisjunction to segregate properly during anaphase to Meiotic nondisjunction - haploid cells that have too many or too few chromosomes many If such a gamete participates in fertilization The resulting individual will have an abnormal The chromosomal composition in all of its cells chromosomal Meiotic Nondisjunction Meiotic In rare cases, all the chromosomes can undergo In nondisjunction and migrate to one daughter cell nondisjunction This is termed ______________________ This ______________________ It results in a diploid cell and one without chromosomes The chromosome-less cell is nonviable The diploid cell can participate in fertilization with a The normal gamete normal Mitotic Abnormalities Abnormalities Abnormalities in chromosome number often occur Abnormalities after fertilization after In this case, the abnormality occurs in mitosis not meiosis 1. Mitotic disjunction 1. 2. Chromosome loss 2. Mitotic Abnormalities Mitotic Genetic abnormalities that occur after fertilization Genetic lead to _____________. _____________. The size and location of the mosaic region depends The on the timing and loca...
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