Chromosomes and Chromosomal Abnormalities Flashcards
What is the name for the short arm of a chromosome?
p
What is the name for the long arm of a chromosome?
q
What is a metacentric chromosome?
Centromere at mid point
What is a submetacentric chromosome?
Smaller p than q arm
What is an acrocentric chromosome?
Virtually no p arm
What is the difference between dark bands and light bands on karyotypes?
Dark bands = gene poor heterochromatin
Light bands = gene rich euchromatin
How many genes can be in a single band?
As many as 50+!
What characteristics are used to identify chromosomes?
- Size
- Centromere position
- Banding pattern
What are 2 ways in which you can get double copies of chromosomes (tetraploidy)?
- Furrow recession during cytokinesis
2. Multiple fertilization
Nondisjunction tends to be associated with _________.
Advanced maternal age oocytes
As many as ___% of spontaneous abortions are due to chromosomal abnormalities.
50%
Noninvasive prenatal screening is helpful for detecting what?
Trisomy 13, 18, 21
The majority of nondisjunction events occur in _____.
Meiosis I
How does FISH work?
Make a probe complementary to a known unique sequence to identify aneuploidy.
How do microarrays work?
Probes are fixed to a slide in unique positions and you wash the sample over the slide.
Make a hybrid of green (control) and red (fetal)
Measures the quantity of DNA…every spot SHOULD be yellow (red + green)
Red or green shows excess or loss of a gene
What is another name for Trisomy 18?
Edwards Syndrome
What are classic Trisomy 18 symptoms?
Rockerbottom feet
Clenched first 2nd and 3rd digits overlapping
Mental retardation, cardiac malformations
What is another name for Trisomy 13?
Patau syndrome
What are classic Trisomy 13 symptoms?
Body patterning is off:
Bilateral cleft lip
Mental retardation
Midline defects: cyclopia, absence of eyes
Congenital heart and urogenital defects
what does t(14;21) indicate in a karyotype?
translocation between chromosomes 14 and 21
What is a Robertsonian translocation?
Translocation involving acrocentric chromosomes
What are common Trisomy 21 symptoms?
Hypotonia Short stature Flat nose Palmar crease Mental retardation Congenital heart defects Early onset Alzheimers
What are common symptoms of Turner syndrome?
Webbed neck Short stature Amenhorrea Gonadal dysgenesis Infertility
What is the genotype of patients with Turner syndrome?
45, X
What are symptoms of Kleinfelter Syndrome?
Long limbs
Hypogonadism
Gynecomastia
Behavioral problems
What is a parAcentric inversion?
A block of DNA on a chromosome that moves AWAY from the centromer
What is a perIcentric inversion?
A block of DNA that moves INVOLVING the centromere
What is a consequence of paracentric inversion?
Unbalanced offspring and genomic instability
What is a consequence of pericentric inversion?
Unbalanced offspring
What is spectral karyotyping (SKY)?
Individual probe sets labelled in 24 different colors–makes it easy to determine origin of extra DNA and for translocations
What test is especially useful for detecting translocations?
Spectral karyotyping
What is a Philadelphia chromosome?
bcr-abl fusion protein formed due to a reciprocal translocation between chromosomes 9 and 22
What disease develops from the formation of a Philadelphia Translocation
Chronic Myelogenous Leukemia
In the case of defective x chromosomes, what are the priorities for inactivation/preservation?
- Preserving activity of one x-chromosome equivalent
2. Preserving autosomal sequences
Can some genes escape X inactivation?
Yes
What is cri du chat?
5p 15 deletion
What are the symptoms of Cri du chat?
Cat cry Mental retardation Microcephaly Epicanthal folds Low set ears Heart defects
