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22 Cards in this Set
- Front
- Back
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Describe a XY female
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Deletion of the SRY gene on the short arm of the Y chromosome. The individual is Turner-like but tall stature
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Describe a XX male
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Copy of the SRY gene is translocated to one of the X chromosomes. The individual is Klinefelter-like but short stature
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Describe a true hermaphrodite
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* It is the condition where both testicular and ovarian tissues are present
* Individual has variable phenotype |
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What are some of the causes of true hermaphroditism?
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* Mosaicism (46 XX / 46 XY or 46 XX / 46 XXY)
* Chimaerism: Two dizygotic embryos (different sexes) which later fuse when cells are totipotent |
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What is mixed gonadal dysgenesis?
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* Defined by presence of testicular tissue AND streaked ovary
* Caused by mosaicism of 46 XX / 45 XO |
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What is pseudohermaphroditism?
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* Defined as disagreement between phenotypic and gonadal sex
* Male pseudohermaphrodite: feminized male * Female pseudohermaphrodite: virilized female CAUSE: abnormal androgen action before birth |
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What is adrenogenital syndrome?
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This is a defect in the synthesis of corticosteroids in the adrenal cortex, inherited as an autosomal recessive trait.
Leads to large-sized adrenal gland. |
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What are some of the symptoms of adrenogenital syndrome?
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* Excessive ACTH secretion
* Excessive synthesis of adrenal androgens * Virilization of the female fetus * Genetic females born with ambiguous external genitilia * Precocious (early) puberty in affected males * Many patients have dangerous electrolyte abnormalities due to lack of mineralcorticoids |
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What is the treatment for adrenogenital syndrome?
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Treat with corticosteroids so as to normalize electrolyte concentrations
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What is testicular feminization?
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This syndrome is caused by a defect of androgen receptors inherited as a X-linked recessive trait
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What is another name for testicular feminization?
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Androgen insensitivity syndrome
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What is the phenotype for someone suffering from testicular feminization?
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* Externally, these individuals have a normal female appearance
* Karyotype is 46 XY * Non-functional testes are present in abdomen / inguinal canal * Ovaries, uterus, fallopian tubes are absent * Height is above the female average * Pubic and axillary hair are sparse (if complete deficiency) * Partial defects of the androgen receptor cause phenotypes ranging from infertile male to phenotypic female |
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What is the present complaint for individuals (with testicular feminization)?
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No menstruation period
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What is the treatment for testicular feminization?
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Sex change operation
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What causes DiGeorge Syndrome?
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Deletion of 3 million bp from chromosome 22
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What is the model of inheritance for DiGeorge Syndrome?
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93% have a de novo deletion, 7% have an affected parent
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What are the clinical presentations for DiGeorge Syndrome?
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* Congenital heart defects: tetralogy, aortic arch defects, septal defects
* Abnormalities of the palate * Characteristic facial features * Mild mental deficiency * Thymus hypoplasia -> immune deficiency * Hypocalacemia (parathyroid gland underdeveloped) * Renal malformations * Autism, schizophrenia |
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What are the causes of chromosomal rearrangements?
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* Chromosome breakage
* Crossing-over between misaligned chromosomes in meiosis |
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What are the types of chromosomal rearrangements that we see day to day?
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* Deletions
* Insertions * Duplications * Translocations * Para- and peri-centric inversions * Isochromosomes |
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What are the consequences of chromosomal rearrangements?
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Depending on the copy number of the genes, we can have one of two consequences:
1. Balanced rearrangements: normal gene dosage 2. Unbalanced rearrangements: abnormal gene dosage |
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What is a Robertsonian translocation?
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A Robertsonian translocation is a type of nonreciprocal translocation in which two nonhomologous acrocentric chromosomes (chromosomes with centromeres near their ends) break at their centromeres, following which the long arms become attached to a single centromere.
The short arms also join to form the reciprocal product, which typically contains nonessential genes and usually is lost within a few cell divisions |
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What is Cri Du Chat syndrome?
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Cri du chat syndrome (French for Cry or call of the cat), also called deletion 5p syndrome, 5p minus or Le Jeune’s syndrome, is a rare genetic disorder due to a missing portion of chromosome 5
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