Term
| Indications for karyotyping |
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Definition
- probs with early growth + development
- stillbirth + neonatal death
- firtility probs
- family hx
- pregnancy - advanced maternal age
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Term
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Definition
- chngs in chromosome #: monosomy, trisomy, polyploidy
- can arise from nondisjunction at meiosis I or II
- diff types of nondisjunction (sis chromatids separate prematurely)
- anaphase lag
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Term
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Definition
- Failure of chromosome to attach to MT at kinetochore and chrom is expelled from cell
- can happen in meiosis I or II with different results
- DRAW!
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Term
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Definition
- short homologous regions on X and Y where recomb can occur
- distal p arm regions and distal q arm regions (rare)
- 13 known genes
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Term
| what is the only viable monosomy? |
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Definition
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Term
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Definition
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trisomic cell can proliferate, monosomic dies
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somatic: occurs in mitosis, stage of development at which nondisjxn occurs determines level of mosaicism in body, lower levels of trisomy
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meiotic (germline): anaphase lag, trisomy rescue, higher levels of trisomy - more severe phenotype
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Hard to diagnose, cannot test every cell type
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Term
| only viable aneuploidies (why are these liveborn?) |
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Definition
- 13: Patau syndrome
- 18: Edward syndrome
- 21: Down syndrome
- XXX: Triple X syndrome
- XXY: Klinefeltersyndrome
- XYY: Syndrome
- monosomy x
- These are small and have relatively few genes
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Term
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Definition
- trisomy 21, most common liveborn autosomal abn
- 66% abort spontaneously
- 1/700-800 births
- most common single cause of mental retardation
- probs req immediate attn: cong. heart def., esophageal, anal, duodenal atresia
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Term
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Definition
- Trisomy 13
- 1/5000-8000 births
- microcephaly, polydactyly, rocker bottom feet, cleft lip, heart defect
- 50% die within 1st 3 months
- 95% die by age of 3
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Term
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Definition
- Trisomy 18
- 1/3000-6000 live births
- 95% spont abort
- pneumonia, apnea, diaphramatic hernia, spina bifida
- complete care, never walk or feed themselves
- 50% die w/in 1st few wks, 95% die w/in 1st yr
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Term
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Definition
- monosomy x, short stature from age 3
- 50% monosomy, 30-40% mosaic, 10-20% isochromosomes, ring chromosomes, deletions
- 80% caused by loss of paternal derived sex chrom during paternal meiosis or early cell division in embryo
- ~98% 45,X spont abort
- low hairline, webbed neck, wide nipples, primary ovarian failure, breasts/ pubic hair absent...
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Term
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Definition
- 47,XXY, 1/500-1000, normal life expectancy, learning disabilities
- 50% spont abort
- male phenotype, tall, elongated forearms + lower legs, gynecomastia, small testes
- frequently azoospermic (atrophy of seminiferous tubules)
- 15% mosaic
- can include 48,XXXY; 49,XXXXY; etc
- paternal in origin in 50% of cases
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Term
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Definition
- 1/1000, tall stature, large teeth, normal fertility
- parental origin is paternal (Y can only come from male)
- despite faulty reports, 47,XYY is not associated with criminal/ anti-social behavior
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Term
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Definition
- 1/1000-1500, tall slender body, mild reduction in intellectual skills,
- 47,XXX; 48,XXXX; 49,XXXXX; etc. the more X's, the more abnormalities
- 25% are infertile
- maternal origin of additional X in 95% of cases
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Term
| Parental origins of aneuploidy |
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Definition
- autosomal trisomies - 85-95% maternal, tris. 16 is 100% maternal
- XXY - approx 50/50
- XXX - 95% maternal
- XYY - 100% paternal
- monosomy x - 80% paternal, 20% maternal (the X that is present in a 45,X conceptus is the maternal X ~80% of the time)
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Term
| Effect of advancing maternal age on risk of aneuploidy |
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Definition
- meiosis I initiated in fetal oocyte, but maj. portions of oogenesis (cell division) occur in adult ovary
- connection bet sister chromatids and bet homologues must be maintained for decades (old cohesins)
- age-related association of decreased REC8 in older oocytes responsible for breaking down cohesin during anaphase - inc risk of meiotic errors
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Term
| Genesis of polyploidy (triploidy and tetraploidy) |
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Definition
- Triploidy
- Diandric: 2 sperm fertilize 1 egg (66%) OR 1 diploid sperm fertilizes egg (24%)
- Digynic: normal sperm fertilizes diploid egg (10%)
- Tetraploidy: normal fertilization, DNA duplication, but no cell division
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Term
| spontaneous abortion stats |
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Definition
- 15% of all clinically recognized pregnancies spont abort
- estimated that 78% of all conceptions fail to go to term
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