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29 Cards in this Set
- Front
- Back
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During interphase what is and isn't condensed?
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Condensed: Barr bodies and heterochromatin
uncondensed: euchromatin chromosomes |
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Anhidrotic Dysplasia
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(absence of sweat glands)
-X-linked recessive, MOSAIC female carriers strippled areas even in indentical twins due to Barr bodies |
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In the lab we like to work with:
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Chromosomes from metaphase because they are condensed for cell division
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What do reagents do to obtain a karyotype:
Phytohemagglutinin colchine trypsin/giemsa |
-starts division of lymphocytes
-blocks division in metaphase (where they are most condensed) -chemical/enzymatic treatment to obtain banding patter |
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What cells are used for adult karyotyping?
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Blood (leukocytes)- culture 2-3 days
bone marrow biopsy- no culture fibroblast (skin) cells: culture 2-3 weeks |
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What cells are used for prenatal karyotypin?
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amniotic cells: culture 2-3 weeks (taken at wk 16)
chorionic villus sample: culture not needed but separation from maternal tissue necessary (week 11) |
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Out of the non-banded karyotypes which groups are acrocentric and what chrom are they?
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Group D= 13-15
Group G= 21-22, Y |
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Dark G bands characteristics:
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later replication, fewer transcriptionally active genes, more condensed, shorter loop, Higher AT, stain with quinacrine
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Polyploidy:
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3 copies of ALL chromosomes,
NOT viable -most common reasons for early pregnancy loss |
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Trisomy:
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excess of 1 chromosome
-only on 13, 18, 21, X or Y are viable -16 most common for preg loss -80% die of trisomy 21 in utero |
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Monosomy:
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lack of one chromosome
-only viable with X (Turner's syndrome) -99% die in utero |
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Structural abnormalities:
del inv dup ins |
deletion
inversion duplication insertion |
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structural abnormalities
r t der/rob iso |
ring
translocation, recipricol translocation, robertsonian isochromosome |
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Isochromosome formation:
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a chromosome with 2 arms
(p-p; q-q) [centromeres were pulled from the end instead of the middle] |
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ring chromosome formation:
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looses telomeres at both ends, instability in cell division (mitosis)
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Down Syndrome symptoms:
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mental retardation
heart defects/ 40%malformations hypothyroidism specific head, hand and feet shape |
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Down Syndrome causes:
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-95% trisomy 21
(usually error in 1st maternal meiosis) -3-4% robertsonian or recipricol t. (chr. 14/21) 1% mosaicism (non-disjuntion in mitosis) |
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What causes early senility in Down Syndrome?
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chromosome #21 has APP (amyloid plaque protein) which gets overexpressed - alzheimers.
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mutations in SOX9 and AR (androgen receptor) leads to what?
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female phenotypes in 46XY
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What does SRY do?
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sex determining region
-without it the gonads stay female |
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what causes ambiguous external genitalia at birth?
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-chromosomal abnormatlity
-single gene disorders -unusual external stimuli -unknown |
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True hermaphrodite "intersex"
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-both ovarian and testicular tissue
-44% ovotestis -most are 46XX (some have SRY) -remainders are either mosaics or chimeras |
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Female intersex:
cause A cause B |
-only has ovaries but virilized (masculinized) phenotype
-A= prenatal exposure to progesterone or androgen -B= inherited deficiency of 11 or 21 hydroxylase in adrenal cortex (adrenogenital syndrome) |
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adrenogenital syndrome
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-mix b/w penis and vagina
-hyperplasia of adrenal cortex- low BP leading to cardiac arrest -hyponatremia and hyperkalemia -treatment with cortisol or surgial reconstruction |
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21-hydroxylase
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95%
-hyponatremia and hyperkalemia -impaired epinephrine release -congenital hypoglycemia -Hirsutism-advanced bone age |
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11-hydroxylase
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5% of classic cases
-normal or hyperkalema -2/3 hypertension -mild form of hisutism -moroccan jews |
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Androgen insensitivity syndrome
(male intersex A) full version |
full= externally female internally undescended testes, primary amenorrhea/infertility
46XY X-linked recessive androgen receptor defect |
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Androgen insensitivity syndrome
(male intersex A) "testicular feminization" partial version |
-partial phenotype,
-nondescended testes should be removed -3rd most common cause of -primary amenorrhea |
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5-alpha-reductase type 2 deficiency
(male intersex B) |
46XY
-partial feminization at birth -wolffian structures present -testes often non-descended -hypospadia -some virilization at puberty -autosomal recessive -testosterone won't convert to more active dihydrotestosterone |
