Genes&Society_1 Colour slide perpage_Lecture2

Normal females are xx heterozygous females are xx and

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Unformatted text preview: andom distribution of orange and black patches demonstrates inactivation. demonstrates X-inactivation. The The white patches are due to another gene (S). Human example: Human example: Anhydrotic Anhydrotic dysplasia is a disease that results in the absence of sweat glands. Normal females are XX, heterozygous females are XX' and have patches of skin with sweat glands and patches of skin without sweat glands. Females that are X'X' do not have sweat glands. 45 Chromosome Chromosome Dynamics: Normal vs. Aberrations (mutations/abnormalities at the chromosomal level) See additional reading material: additional reading material: Chromosomal aberration.pdf 46 Normal Normal Homologous Recombination (occurs in testis and ovary) From From diploid germ cells To haploid To haploid Sex Sex Cells (gametes) 47 Translocation Translocation 48 Insertion Insertion 49 Deletion Deletion Duplication 50 A representative karyotype and a photograph of a child representative exhibiting cri-du-chat syndrome (46,5p-). In the karyotype, the cri-du(46,5parrow identifies the absence of a small piece of the short arm of one member of the chromosome 5 homologs. th Affected individuals have wide-set eyes, a small head and jaw and are wide51 moderately to severely mentally retarded and very short. When When chromosome segregation fails…... segregation Normal case acquire extra copy eg. Chrom. 21: Down’s syndrome 52 Nondisjunction Nondisjunction during the first and second meiotic divisions. In both cases, some of the gametes that are formed either contain two members of a specific chromosome or lack that chromosome. After fertilization by a gamete with a normal haploid content, monosomic, disomic (normal), or trisomic zygotes are produced. 53 The The karyotype of a child with Down syndrome. In the karyotype, three members of the G-group chromosome 21 are present, Gcreating the 47 creating the 47,21+ condition. condition Characteristics include decreased muscle tone asymmetrical skull Characteristics include decreased muscle tone...
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