Study your flashcards anywhere!

Download the official Cram app for free >

  • Shuffle
    Toggle On
    Toggle Off
  • Alphabetize
    Toggle On
    Toggle Off
  • Front First
    Toggle On
    Toggle Off
  • Both Sides
    Toggle On
    Toggle Off
  • Read
    Toggle On
    Toggle Off

How to study your flashcards.

Right/Left arrow keys: Navigate between flashcards.right arrow keyleft arrow key

Up/Down arrow keys: Flip the card between the front and back.down keyup key

H key: Show hint (3rd side).h key

A key: Read text to speech.a key


Play button


Play button




Click to flip

45 Cards in this Set

  • Front
  • Back
What is aneuploidy?
An abnormal number of chromosomes
What are the 3 most common autosomal aneuploidies?
-Trisomy 21 (Down)
-Trisomy 18 (Edward)
-Trisomy 13 (Patau)
Why don't we ever see autosomal deletions, only duplications?
Because you can't survive without one of your autosomes.
What are 3 types of down syndrome?
-Free trisomy 21
-Translocation Down's syndrome
-Partial trisomy (mosaic)
What is the cause of 95% of downs syndrome cases?
Maternal nondisjunction
What are the 4 common physical features of DS patients?
-mongoloid (epicanthic folds)
-flat occiput
-short broad hands
-large tongue - macroglossia
What congenital defects are DS patients apt to have?
-Cardiac (ASD/VSD, AV canal defects)
-Duodenal atresia
What are 2 diseases that patients with DS often develop?
-Alzheimer's disease
What is the incidence of Down's syndrome in the general population?
What is the incidence of DS in parents that already have 1 child with it?
1/100 (a 1% increase)
What is 4% of DS cases?
Translocation trisomy 21
What occurs in translocation trisomy 21?
Attachment of 21 to the short arm of a chromosome (13,14,15, 21, or 22), so there is a normal number of chromosomes but 3 copies of 21
What is the chromosome number in the parent that carries the translocation?
What sex is more predisposed to being a translocation carrier?
What is 1% of Down syndrome?
What causes DS mosaicism?
Mitotic nondisjunction
What is mosaicism?
A mixture of cells in patients
-some have normal chromosomes
-some have trisomy 21
When does DS mosaicism develop?
Early in embryonic development
How do Trisomy 13 and 18 compare to 21?
Much more severe, low long term survival rate.
What are the features of Trisomy 13?
-Cleft lip/palate
-Prominent calcaneus
What are the features of Edwards syndrome (trisomy 18)?
-overlapping digits
-Profound developmental delay
-Severe heart defects
What is the incidence of
-Patau syndrome
-Edward syndrome
Patau - 13 - 1/15000
Edward - 18 - 1/8000
What is the smallest cytogenetically visible fragment of DNA?
3 to 5 million base pairs - ONE BAND
How many genes are on average contained in one band?
How many extra genes are conferred in trisomy 21?
What is the chromosome abnormality in Turners syndrome?
What are the common physical features of 45x turner syndrome?
-Short stature (4'10")
-Broad webbed neck
-Absence of menarche
Why is there a broad webbed neck?
Due to edema in utero
Why are girls with Turner syndrome sterile?
Because their oocytes involute prior to birth
What is the cause of 75% of turner syndrome?
Loss of the PATERNAL sex chromosome
What is the incidence of Turner syndrome in live births?
What happens to the VAST MAJORITY (99%) of babies with 45X?
They are lost before term
So is 45X very compatible with life?
What are the intellectual capacities of girls with Turner syndrome?
Normal - not retarded, but may have spacial perception deficits.
What is the chromosomal abnormality in Klinefelters syndrome?
What are the features of Klinefelters syndrome?
-Tall feminized features
-Low androgens
-Small testes
-Fat distribution is abnormal
What is the incidence of Klinefelter's?
What is the IQ of Klinefelters syndrome patients?
Can males with Klinefelters have children, if they're infertile?
Yes; there are SOME cells with normal karyotypes - in islands in the testes.
How can a person survive with only one X chromosome?
All people have an inactivated X chromosome anyway.
Then why are patients with Turners and Klinefelters phenotypically different?
Because there are SOME X chromosomes that escape inactivation in normal people.
So what happens as the number of extra X chromosomes increases?
Developmental delay increases in severity
What does an extra Y chromosome do?
-Makes you tall
-Gives you large canines
-Makes you fertile
-Makes you go to prison bc you're mentally subnormal
What is the karyotype of most males with an extra Y?
47 XYY
What is the incidence of 47 XYY?