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14 Cards in this Set
- Front
- Back
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Presence of two different cell lines in the body that came from 1 zygoye
-due to mitotic non-disjunction, NOT inherited |
Mosaicism
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Are all cells derived from the mosaic cell, mosaic too?
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Yes, all cells derived from that abnormal cell willbe mutated as well.
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Is mosaicism occur before the zygote forms or after?
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After the zygote formed therefore it is not inherited
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Are individuals who are mosaic at risk of passing on the mutation to offspring?
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Yes, if the germline cells carry the mutation.
The offspring WILL NOT be mosaic, they will carry the mutation in all their cells |
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Example of mosaicism?
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Segmental Neurofibromatosis
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Mosaicism present in germ cells.
Due to a mutation that occurs after fertilization in Mitosis NOT meiosis. Portion of the germ cells have a mutation that parent does not express |
Germ line mosaicism
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-Mutation after fertilization, non-disjunction
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Somatic mosaicism
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-One cell line is preferentially inactivated
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Skewed X-inactivation
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X-linked recessive: Female carriers may express phenotype
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If a higher percentage of normal X chromosomes were inactivated, majority of cells will express the mutation.
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X-linked dominant: Females with mutations may have milder expression than males
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Females who carry mutation may not exhibit expected phenotype
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Example of females with mutations that have mild expressions than males
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Rett syndrome: female w/ no or mild clinical expression.
May have child who is severely affected |
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What is a clinical example of conditon involving multiple factors affecting inheritance patterns?
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Hereditary Hemochromatosis
This is an autosomal recessive condition, which leads to excessive iron storage in the body. Most commonly inherited condition in the U.S |
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Multiple manifestations of Hereditary Hemochromatosis
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1. Bronze/gray skin
2. Arthritis and joint pain 3. Heart arrhythmias or failure 4. Diabetes mellitus 5. Liver cirrhosis or cancer 6. Impotence, early menopause, or menstrual irregularity |
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Hereditary Hemochromatosis demonstrates?
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1. Reduced penetrance: Not everyone with 2 mutations will develop hemochromatosis
2. Variable expressivity: individuals with HH may present very differently 3. Pleiotropy: multiple organ systems affected 4. Locus heterogeneity: usually due to HFE gene mutations, but 3 other genes are known 5. Allelic heterogeneity: 3 common mutations: C282Y most severe 6. Delayed age of onset: typically does not develop until adulthood 7. Phenocopies: hemochromatosis may develop due to acquired conditions such as alcoholic liver disease or hepatitis 8. Sex-influenced: more common in males than females b/c of the protective effect of menstruation by reducing iron content |
