CYTOGENETIC DISORDERS PART 1 Flashcards
Diseases with abnormal
chromosomal number or
alterations in structure of one or more chromosomes
Cytogenetic Disorder
Types of Cytogenetic Disorders
- Chromosome Aneuploidy Syndrome
- Autosome and Sex Chromosomes
- Structural Chromosome Anomalies
- Microdeletion Syndromes and Contiguous
- Gene Syndromes
Complete sets of chromosome with none extra or missing.
Euploidy
The normal human cells are diploid, having two sets of
23 chromosomes.
One or more individual
chromosomes are extra or missing from a euploid set.
Aneuploidy
Missing pair of Homologs, occurs at preimplantation stage and It is Lethal.
Nullisomy
One chromosome is missing, occurs at embryonic stage and Lethal.
Monosomy
Three copies of a particular
chromosome, occurs at embryonic or fetal stage and maybe lethal.
Trisomy
Differentiate between Triploidy and Trisomy.
Triploidy has three sets of
chromosomes while Trisomy two sets with one chromosome that has an extra copy.
Example of this is Down Syndrome
Trisomy
Example of this is Tuner’s Syndrome
Monosomy
The involved chromosomes are
autosomes.
Autosomal Aneuploidy
Trisomy 13
Patau Syndrome
Trisomy 18
Edward Syndrome
Trisomy 21
Down Syndrome
Among the three examples of Autosomal Aneuplodies, what trisomy/ syndrome having more cases? What is the ratio?
Trisomy 21 or Down Syndrome, since it has the ratio of 1:700.
The ratio of Trisomy 13 or Patau syndrome is
1:4,000 to 1:15,000
The ratio of Trisomy 18 or Edward Syndrome is
1:8,000 livebirths
Causes of Trisomy 21 and 13 is
Nondysjunction, Mosaic, and Translocation
Causes of Trisomy 18 or Edward Syndrome is
Nondysjunction and Mosaic
Most common causes in Trisomy 21 or Down Syndrome is
Nondysjunction
These three conditions in Autosomal Aneuploidies are associated with
Increased Maternal Age
Life expectancy of patient with Down Syndrome
Up to the 2nd/3rd decade
of life, usually.
Life expectancy of patient with Patau Syndrome & Edward Syndrome
Less compatible with life, that patients usually die within the first month of life.
(1st month of life)
Most common of the chromosomal disorders and it is the major cause of Mental Retardation.
DOWN SYNDROME
SOME FEATURES OF AN INDIVIDUAL WITH DOWN SYNDROME
-Epicanthic Fold with Flat Facial Profil
-Mental Retardation
-Abundant Neck Skin
-Simian Crease
-Umbilical Hernia
-Heart Defects (40%)
-Leukemia
Simian Crease means
The line in the palm is straight from one side to the other side