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22 Cards in this Set

  • Front
  • Back
Describe a XY female
Deletion of the SRY gene on the short arm of the Y chromosome. The individual is Turner-like but tall stature
Describe a XX male
Copy of the SRY gene is translocated to one of the X chromosomes. The individual is Klinefelter-like but short stature
Describe a true hermaphrodite
* It is the condition where both testicular and ovarian tissues are present

* Individual has variable phenotype
What are some of the causes of true hermaphroditism?
* Mosaicism (46 XX / 46 XY or 46 XX / 46 XXY)

* Chimaerism: Two dizygotic embryos (different sexes) which later fuse when cells are totipotent
What is mixed gonadal dysgenesis?
* Defined by presence of testicular tissue AND streaked ovary

* Caused by mosaicism of 46 XX / 45 XO
What is pseudohermaphroditism?
* Defined as disagreement between phenotypic and gonadal sex

* Male pseudohermaphrodite: feminized male

* Female pseudohermaphrodite: virilized female

CAUSE: abnormal androgen action before birth
What is adrenogenital syndrome?
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.
What are some of the symptoms of adrenogenital syndrome?
* 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
What is the treatment for adrenogenital syndrome?
Treat with corticosteroids so as to normalize electrolyte concentrations
What is testicular feminization?
This syndrome is caused by a defect of androgen receptors inherited as a X-linked recessive trait
What is another name for testicular feminization?
Androgen insensitivity syndrome
What is the phenotype for someone suffering from testicular feminization?
* 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
What is the present complaint for individuals (with testicular feminization)?
No menstruation period
What is the treatment for testicular feminization?
Sex change operation
What causes DiGeorge Syndrome?
Deletion of 3 million bp from chromosome 22
What is the model of inheritance for DiGeorge Syndrome?
93% have a de novo deletion, 7% have an affected parent
What are the clinical presentations for DiGeorge Syndrome?
* 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
What are the causes of chromosomal rearrangements?
* Chromosome breakage

* Crossing-over between misaligned chromosomes in meiosis
What are the types of chromosomal rearrangements that we see day to day?
* Deletions

* Insertions

* Duplications

* Translocations

* Para- and peri-centric inversions

* Isochromosomes
What are the consequences of chromosomal rearrangements?
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
What is a Robertsonian translocation?
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
What is Cri Du Chat syndrome?
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