Cytogenetics Flashcards
What is cytogenetics?
The study of chromosomes and their structure, inheritance, and abnormalities
Which arm of the chromosome is the long arm? Which is the short arm?
Long= q; short= p
During which stage of mitosis are chromosomes best visualized?
Metaphase
Which class of chromosome structure has the centromere directly in the center of the chromosome?
Metacentric
Which human chromosomes are telocentric?
None
What class of chromosome structure has the centromere very near the end of the chromosome?
Acrocentric
What technique enables the identification of individual chromosomes by producing characteristic light and dark bands?
G-banding
What are the two types of chromatin visualized via G-banding?
Dark staining= Heterochromatin; Light gray or white= euchromatin
What is the name of the lab techniqu in which fluorescently labeled fragment of cloned DNA (probe) is allowed to pair with its complementary sequence on the chromosome directly on the microscope slide
Fluorescence in situ hybridization
What is polyploidy?
Any abnormal multiple of the haploid chromosome number
What is aneuploidy?
Any number of chromosomes that is not diploid
What is the most common cause of aneuploidy?
Nondisjunction
What is the most common cause of triploidy?
Simultaneous fertilization of one egg by two sperm
What is the chromosomal basis of Down Syndrome?
Trisomy 21
What is the most common trisomy?
Trisomy 21
What are the principle features of Down Syndrome?
Flat facial profile, prominent epicanthal folds, cardiac structural defects, GI obstructions, Early onset Alzheimer’s, hearing deficits
What chromosomal abnormaility is the basis of Patau Syndrome?
Trisomy 13
What symtoms/ features are associated with Trisomy 13?
Cleft lip/palate, congenital heart defects, incomplete brain development (holoprocencephaly), apneic spells, polydactyly, low set deformed ears
What is the chromosomal basis of Edwards Syndrome?
Trisomy 18
What are the common clinical features of trisomy 18?
Clenched hand, deformed digits, rocker bottom feet, low set malformed ears, short sternum, congenital heart defects
What is the karyotype associated with Turner syndrome?
45, X
What is the typical presentation of Turner Syndrome?
Very short stature, absent/abnormal ovaries, sterility, broad chest, lymphedemia–> webbed-neck, bone anomalies
What karyotype is associated with Klinefelter Syndrome?
47, XXY
What are the common clinicial features of Klinefelter Syndrome?
Males w/ infertility, small penis and testes, enlarged breasts, sparse body/facial hair, tall stature, long limbs, dull mentality/behavioral problems/ learning difficulties/ austism common
What causes mosaicism?
Nondisjunction after conception
What is the basis of Cri du Chat syndrome?
deletion of the short arm of chromosome 5 (5p-)
What are the features associated with Cri du Chat?
Low birth weight, slow growth, microcephaly, mental deficiency, abnormal facial features, enlarged tongue
What is a balanced translocation?
A translocation in which there is an even exchange of material with no extra or missing genetic information
Translocation 14; 21 inheritance may cause what condition?
Down syndrome
What are the chances that carriers of translocation 21;21 will have an abnormal child?
100%- either Down syndrome or non-viable monosomy 21
The majority of all Down syndrome patients have what karyotype?
47, +21
What chromosomal changes are unique to cancer? From what are they likely derived?
Double minutes and homogenously staining regions; MYC oncogene amplification
What technique is a variation of FISH that allows for the detection of copy number changes?
Comparative Genomic Hybridization
