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25 Cards in this Set
- Front
- Back
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Basic system of nomenclature
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distinguished by length, centromere location, light/dark patterns.
short arm (p), long arm (q) metacentric, centromere in middle submetacentric-centromere off center acrocentric-centromere near one end 13,14,15,21 have satillites, attached to short arms Giemsa staining-light dark bands, numbered location of band. |
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How to test for Chromosomal abnormalities
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FISH-visualize single gene, chromosomal region, or entire chromosome. Chromosome is mixed with fluorscent label, visualized. is a portion delated, translocated, small,
one set-deletion excess-more then 4 places |
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Abnormalities of Chromosome Structure
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translocations, balanced and imbalanced, unbalanced-death sab
any change can cause abnormal development Reciprocal translocations-exchange of nonhomologous chromosomes. unbalanced trans--partial monosomy, partial trisomy, increased risk for offspring, infertility S.ab. |
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How to test for Chromosomal abnormalities
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CGH-directly compared DNA to control-normal DNA. red and green, hybridized, imbalance in ratio tells you if too much or too few copies, multiple fish at once, specificity is low,
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Aneuploidy
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Aneuploidy (abnormal chromosomal number) physical or congenital development from nondisjunction at 1st or 2nd meiotic divisions; nost incapatable with life
Trisomy-3 copies of genes, gamete with 2 copies gamete of one copy (trisomy 21, most common) Monosomy-gamete of one copy, gamete of zero. not compatiable with life extra maternal chrom-Sab |
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Balanced translocation
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detected, testing of parents is recommended.
de novo, increased risk, of phenotypic ab, subtile, disruption of genes at bkpt |
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Deletion
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intersititail, or terminal
routine karyotyping use FISH--di george syndrome |
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Duplication
marker Chromosome |
partial trisomy-depends on size for damage
small additional chromosome, super numery chromosomes, |
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ring chromosome
inversion isochromosome |
ab chrom, telomere of each arm connect to other end
two breaks flip 2 copies of 1 arm, 0 of other |
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5 indications of karyotypeing
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1) problems with early growth/development
2)Patients with suspected, recognizable symptoms 3)Stillbirth/neonatal death 4)fertility problems 5)Family history 6)Preg in women of advanced age |
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Genetic Screening (newborn)
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indentify disorders for which there are 1. early treatment prevents disease, 2. low false postive, low false negatives. 3.PKU is the prototype; PKU, galactosemia, congenital hypothyroidism, sickle cell disease
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Heterozygote screening (carrier)
ppl who are healthy, but risk to children |
1. disorder of severity of warrent screening
2. High freqency of carriers in pop 3. inexpensive and dependable test, low FP/FN 4.access to genetic counsiling 5. prenatal diag avaliable 6. accept and volutary participation |
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Ashkenazi Jew
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Tay achs, canavan disease, familial dysantonomia, cystic fibrosis
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Caucasians,
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cystic fibrosis
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african, african american, mediterranea
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sickle cells anemai, betal thalassemia
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south east asian
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alpha thallsemia
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controversy of CF screening
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blanket screen, somewhat complex, CF varys among different pop. limitations of screen, most common mutations
negative test does not rule out. |
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prenatel screening
prenatel diagnosis |
PS-noninvasive tests to identify women at high enough risk to warrant invasive procedures. cannot detect all pregnancies
PD-genetic diag testing. supply at risk families with information so they can make an informed choice during pregnancy. benifits reassurance, risk informaition, prepair for birth, plan for delievery, provide risk information to couples for with terminiation is an option. |
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Prenatal screening
AFP Ultrasound |
AFP-fetus iwth NTP increases levels of alpha fetoprotein (AFP) in amniotic fluid--AFP is elevated in maternal serum (MSAFP). abnormal MSAFP, diag amnio/US. Expanded unconjugated estriol and HcG to screen of DS and trisomy 18. Triple screen.
DS-decreased AFP, increased hCG. Tri 18-decreased in all 3 US-screen for DS, and NTD--accumulate fluid under skin back of neck. Nuchal translucency with mAge risk of DS. US detect abnormalites/characterist features (short bones) |
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Prenatal diagnosis--for karotyping
amniocentesis CVS Preimplantation genetic diag |
amniocentesis-15-20wk GA. remove amniotic fluid, karotyping, and AFP
CVS- biopsy of placenta preformed earliers, decreased anxiety for patients at risk-fisrt trimester term PGD-take one cell, prior to reimplantation IVF |
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triple screen
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DS-decreased AFP, decrease uE3, increased hCG, increased inhibin A
NTD (open)-increased AFP, no change in uE3, inhibin A, hCG Trisomy 18-all are decreased, no change in inhibin A |
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indications for prenatal dx
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1. advanced maternal age
2.abnormal screening results (AFP, NT) 3. previous child with chromosome ab 4. presence of structural chrom abnormality such in parent 5. parents are carriers of tay sacs 6. abnormalites in US |
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Screening of NTDs
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detailed US, level II US, fetal survey, use family history, carrier status
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gene/environment NTDs
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Folic acid is required for development (iron). reduced folate leves, elevated homosystenine levels, no bueno, folate is a part of dividing cells Nucleotide syn so we totally folate. exacerbated with 5,10 MTHFR gener. converts to the major form of folate. if C677T allele is gone, dysfuctional, elevated homocysteine, decrease folate.
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Genetic symdrome
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a pattern of malformations and features result form a single etiology. involve chromosome, dealtion of region, single gene mutation.
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