Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
8 Cards in this Set
- Front
- Back
|
Most common liveborn trisomy
Incidence is about 1/800 births Higher incidence in children of mothers over 35. |
Down Syndrome
Trisomy 21 |
|
|
-The inactivated X chromosome in a cell
-Males do NOT have a Barr body -Number of barr bodies is one less than the number of X chrom. |
Barr bodies
|
|
|
X & Y chrom. share genes within this region
-The region that pairs during meiosis and crossing over takes place |
Pseudoautosomal genes
|
|
|
Abnormal cross-overs between regions of the X and Y can lead to
|
XX males
XY females |
|
|
Is the inactive X completely turned off?
|
No, there are regions of the X that remain activew both within & outside the pseudoautosomal region.
|
|
|
Any daugtgher cell derived from that cell has the SAME X chrom. turned off
|
Clonal inactivation
|
|
|
When is inactivation of X not random?
|
1. A structurally abnormal X chrom. is often preferentially inactivated.
2. Normal X chrom. is often preferentially inactivated if the other X chrom. has autosomal genes on it due to a translocation. |
|
|
What are 2 clinical disorder of sex chromosomes?
|
1. Klinefelter syndrome: males 47, XXY
2. Turner syndrome: females 45, X |
