Card Set Information
What is cytogenetics?
The study of diseases related to chromosomal abnormalities
What is the leading cause of pregnancy miscarriage?
In what stage are chromosomes viewed for cytokenetic studies?
Metaphase - Mitosis
What is the difference b/t metacentric, submetacentric and acrocentric chromosomes?
centromere at center
centromere farther from center
centromere closer to telomere near end where p-arm is really short
What are the four values of utilizing
2) gene amplification
3) abnormal karyotype detection
4) cancer studies
Gain of one or more chromosome sets
and what are two results of it?
gain or loss of one chromosome
trisomy or monosomy
What causes aneuploidy?
Dysjunction at Meiosis I or II
Are monosomies lethal or viable?
What are the three viable trisomy chromosomes?
13, 18, 21
What is the disease related to Trisomy 21 and what are its symptoms (3)?
distinct face, GI problems, Heart defects
At what age does the incidence of Trisomy 21 increase?
>35 (although more incidences happen at younger ages just because more babies are born at this time)
What is the disease associated with Trisomy 18 and what are its symptoms (6)?
low weight, mental retardation, clenched fist, overlapping fingers, small eyes, omphlaocele (gut opened)
What is the disease associated with Trisomy 13 and what are its symptoms (3)?
cleft palate, postaxial polydactyly, large, triangular nose
What type of disease is Turner syndrome and what are its symptoms (2)?
Monosomy, 45 XO
: webbed neck, short stature
What is klinefelter syndrome and what are its symptoms (4)?
Trisomy, 47 XXY
tall, sterile, gynecomastia, small testes
Why is the SRY gene important?
It is what makes a male a true male. It is found on the Y chromosome
How does an XX male form?
The SRY gene is crossed during synapse of the pseudoautosomal region onto the X chromosome
How does and XY Female form?
The SRY gene is crossed over to the X chromosome and the Y is passed on to the female
What is translocation?
exchange of genetic material between non-homologous chromosomes
How does a
Two parts of two chromosomes break and fuse with the other chromosome (3 with 6 and 6 with 3)
What are the percentages of offspring when a
25% gen. abnormal, phen. normal
50% gen/pen abnormal
What is unique about a
compared to a
Only on acrocentric chromosomes (centromere by telomere at small p-arm)
What is the karyotype count for a Roberstonian trans.?
45, b/c they lose two short arms and gain one long arm
What is the chance of a robertsonian mother bearing a down syndrome child?
What are the three types of chromosomal deletions (TIR)?
What is a
single break and loss of one end of the chromosome
What is an
break at two places in an arm and fusion of the blunt ends
What is a
Two broken tips that cause the chromosome to fuse in ring form
What are the two types of inversions?
involving the centromere
not involving the centromere
***when they come together the cut pieces flip before inserting
What is PKU?
Autosomal recessive disease
phenylalanine builds up and is also
converted to an acid
What type of disease is Tay-Sachs and what population receives it most often?
How does Preimplantation genetic diagnosis (PGD) work?
Have to be
one of the 8 cells removed for testing of Tay-Sachs or other heterozygote diseases
What are the four methods for prenatal screening and what part do they test?
1) CVS- fetal tissue
2) NTU- maternal blood/visual
3) Amniocentesis- amniotic fluid
4) ultrasound - visual
What does a high AFP and a low AFP tell about a fetus?
risk for Neural Tube defect (NTD)
risk for trisomy
What two prenatal tests can be used for NTD and Trisomy?
NTU and Amniocentesis
At what weeks should the four tests be performed?
1) CVS 9-12 wks
2) NTU 11-14 wks
3) Amniocentesis 15-17 wks
When should a triple screen be performed?
What is extra in a quadruple test?
inhibin-A (to help measure down syndrome)
What are the three main enzymes tested in triple/quadruple test?