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2-27-03 Chromosome Linkage Disorders Dependent on each other. One broken chain link affects all. Ex: Allele #3 usually crosses over alone. With a disorder, it takes #7 with it. Some genes tend to always cross over with another gene combination, though. Ploidy [chromosome count] disorders Monoploidy- missing one chromosome of a homologous pair Triploidy- has an extra chromosome for a homologous pair (replicated chromosomes did not split) Polyploidy- an excess of the whole chromosome count (extra sets) Sex-linked Turner Syndrome- Only on sex chromosome-X, so genotype is X_. Just enough estrogen to be female. Never truly grows into a woman. Infertility. Klinefelter Syndrome- non-disjunction: failure of replicated chromosomes to separate. Starts out as genotype XXY, but eventually one X turns into a Barr Body and becomes XxY.
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