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50 Cards in this Set
- Front
- Back
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What is the name for the study of chromosomes and their abnormalities?
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Cytogenetics
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What is a euploid chromosome?
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A chromosome containing a mulitple of the normal 23 genes
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What is an aneuploid?
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A chromosome containing a number of genes that is not a multiple of 23. May have a missing or an extra chromosome.
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Will a fetus w/a missing chromosome survive?
With an extra? |
Missing a chromo -- will not survive
Extra chromosome -- may survive, but will have defects |
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What is a karyotype?
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Layout of a person's chromosomes by size.
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What is metacentric (referring to a chromosome)?
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Centromere is in the middle. Arms are equal length.
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What is acrocentric (referring to a chromosome)?
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Centromere is near tip. Arms are unequal.
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What is submetacentric (referring to a chromosome)?
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Centromere is anywhere except in middle or near tip.
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What kind of chromosome does 13q23 describe?
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Chromosome 13
q = long arm (p = petite arm) 2 = band 2 3 = region 3 |
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What is the karyotype for a normal female?
Male? |
Female 46xx (46 chromosomes)
Male 46xy |
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What does monosomy mean?
Trisomy? |
monosomy = missing 1 chromo
trisomy = has extra chromo |
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What is non-disjunction?
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The failure of homologous CHROMATIDS to segregate during MEIOSIS with the result that one daughter cell has both of a pair of chromatids and the other has none.
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At what age do women start to have babies with increased chance of defects?
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35 yo
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What is trisomy 21?
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Down syndrome.
47xy + 21 |
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What are features of Down syndrome baby?
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- palpebral fissure upslant
- flat maxillary region - short neck - hypotonia - increased risk for leukemia - congenital heart defects - GI obstructions - MR |
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What is anticipatory guidance?
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Anticipating course and problems of abnormality and guiding/counselling patient based on acquired knowledge
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What factors contribute to variations in Down symptoms?
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- genetics
- environment - mosaicism |
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What is the major cause of Down syndrome?
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Non-disjunction
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What is translocation?
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A piece of a chromosome breaks off and attaches to another chromosome. The original pair is still there.
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How long do babies w/ autosomal trisomy live?
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Usually on 1-2 years.
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Children with what trisomy can live into the first decade?
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Down syndrome
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What is another name for Trisomy 18?
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Edwards syndrome
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What are the characteristic features of an Edwards syndrome baby?
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- Elfin features
- SGA (small for gestational age) - fingers 1,4 overlap 2,3 in fist - usually die w/in 1st year if it survives at all |
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What is the main heart defect of a Trisomy 18 (Edwards syn) baby?
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VSD -- ventricular septum defect
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What is the main heart defect of a Trisomy 21 (Down syn) baby?
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AV (atrioventricular) canal defect.
Atrioventricular (AV) canal defect is a large hole in the centre of the heart. The defect is situated where the septal wall between the upper chambers (atria) joins the septal wall between the lower chambers (ventricles). In addition, the tricuspid and mitral valves (the atrioventricular valves), which normally separate the heart's upper and lower chambers, are not formed as individual valves. Instead, one large valve bridges the defect. |
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What chromosome is "extra" in Patau syndrome?
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chromosome 13
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What are characteristics of Trisomy 13, Patau syndrome?
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- cleft palate
- atrial septal defects - inguinal hernia - MR |
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What trisomy test is frequently ordered for older mothers?
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13-18-21
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In non-disjunction, what happens if the "empty" egg gets a "y" sperm?
"x" sperm? |
y sperm = no viability
x sperm = survivable |
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What is the chromo description of Turner Syndrome?
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45x
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What are the characteristics of Turner Syndrome?
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- female
- short - webbed neck - no 2º sex chars. - possible MR - possible congenital heart defects |
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Why is Turner Syndrome sometimes diagnosed at puberty?
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It can be seen that puberty does not happen.
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Is there any treatment for Turner Syndrome?
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Hormones if diagnosed early.
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Does mosaicism play a part in Turner Syndrome?
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Mosaicism is believed to play a part in Turner Syn
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What is the chromo description for Kleinfelter Syndrome?
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47xxy
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What are features of Kleinfelter?
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- tall
- long limbs - gynecomastia - small testes - learning disability |
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What disease risks do Kleinfelter Syn patients run?
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- osteoporosis
- breast cancer |
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Are symptoms obvious or mild in Kleinfelter Syn?
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Mild. May not be diagnosed until later, when male discovered to be infertile
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Is there treatment for Kleinfelter Syn?
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Testosterone, if caught early, but it rarely is.
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What is the result of multiple x's + y, e.g., xxxxxy?
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The more x's the more MR
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What symptoms does an xxx female display?
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Very mild or no symptoms
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What is xyy?
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It has no name. Male may be taller and/or have minor behavioral disorders?
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What is the chromo characteristic of Fragile X Syndrome?
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The distal en of one X looks like it is falling off.
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What is the phenotype of Fragile X Syndrome?
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- large head and ears
- long face - mild to severe MR |
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What is the defective gene in Fragile X Syndrome?
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FMR1 -- fragile mental retardation 1
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Is Fragile X Syndrome inherited?
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Frequently
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How is Fragile X Syndrome usually handed down?
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More frequently mother --> son
(oogenesis) |
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What is "anticipation"?
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Anticipation --> frequency and severity of disorder increases w/subsequent generations
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In Fragile X Syndrome, what DNA sequence nucleotide triplet is repeated over and over?
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CGG
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What is the relation between # of repeats and severity of Fragile X Syndrome?
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The more repeats, the greater the severity
5 - 50 Normal 50 - 200 Pre-mutation >200 Affected |
