GROUP TOPIC: Down Syndrome Flashcards
A genetic condition in which a person has an extra copy of chromosome 21, for a total of 47 chromosomes instead of 46.
Down Syndrome
Causes
__________-
Most common
About 95% of people with Down syndrome have trisomy 21
It occurs when a developing fetus has 3 copies of chromosome 21 in every cell instead of the typical two copies.
________—chromosomes don’t split apart
Causes
Trisomy 21
Most common
About 95% of people with Down syndrome have trisomy 21
It occurs when a developing fetus has 3 copies of chromosome 21 in every cell instead of the typical two copies.
Nondisjunction—chromosomes don’t split apart
Causes
-This type accounts for less than 4% or 3% of all cases.
-It occurs when a portion (part or a whole) of chromosome 21 becomes attached (translocated) onto another chromosome, before or at conception.
-In short, unlike trisomy 21, translocation occurs when chromosome 21 isn’t separate, but it relocates to another numbered chromosome.
-part of two chromosomes switch.
Robertsonian translocation
Causes
The rarest type (1% in all cases)
People with_____ Down syndrome may have fewer features of the condition
This_____ of normal and abnormal cells is caused by abnormal cell division after fertilization
It occurs when only some cells contain the usual 46 chromosomes and some cells contain 47. The extra chromosome in some cells is chromosome 21.
Cells mixed
Mosaic
Causes
-increased risk for increased aged pregnancy.
Maternal age
TESTS
-
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Second trimester
-
-
First trimester
Blood tests
Cell-free DNA test
Ultrasound (nuchal translucency test)
Second trimester
Blood tests
Ultrasound