Chapter 6: Clinical Cytogenetics: Disorders of theAutosomes and the Sex Chromosomes Flashcards
mutations in what gene are associated with aneuploidy?
Bub1 gene
Does the mutation of the Bub 1 gene affect offspring when it’s seen in the egg or sperm?
egg
-loss of a small segment from one
chromosome of a pair, results in hemizygosity
Segmental aneusomy
-results from a microdeletion of chromosomal DNA extending over two or more continuous loci
-Phenotype is due to haploinsufficiency for multiple contiguous
genes or a single gene
-Deletions produce syndromes that are clinically recognizable,
can be detected using FISH or array CGH
Contiguous gene syndrome
-are the result of a sequence–dependent
mechanism involving aberrant recombination between low-copy
repeated sequences
Genomic disorders
what microdeletion is common and frequently evaluated in clinical cytogenic labs?
chromosome 22q11.2 microdeletion
-Autosomal dominant conditions caused by a 3 Mb deletion within
22q11.2, removes about 30 genes
-Detected in 1 in 2,000 to 4,000 live births
-Patients have characteristic craniofacial anomalies, mental
retardation, and heart defects
Chromosome 22q11.2 microdeletion
Which chromosome is relatively gene poor?
Y chromosome
Where is the Testis-Determining factor (TDF) located? What does it do?
on Yp acts as a switch to divert development into male pathway forming testes
Where is the Sex-determining Region (SRY) gene located? What does it do?
on the Y gene - encodes a DNA-binding protein that likely functions as a transcription factor
If SRY/TDF is present what occurs?
male
If SOX 9/DAX1 induce SRY what occurs?
production of testes
If SOX9 is deleted in a man, what do you get?
46XY female
If SOX9 is duplicated in a female, what do you get?
46XX male
What is AZF needed for?
spermatogenesis and external genitalia
