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25 Cards in this Set

  • Front
  • Back
Basic system of nomenclature
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.
How to test for Chromosomal abnormalities
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
Abnormalities of Chromosome Structure
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.
How to test for Chromosomal abnormalities
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,
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
Balanced translocation
detected, testing of parents is recommended.

de novo, increased risk, of phenotypic ab, subtile, disruption of genes at bkpt
intersititail, or terminal

routine karyotyping use FISH--di george syndrome

marker Chromosome
partial trisomy-depends on size for damage

small additional chromosome, super numery chromosomes,
ring chromosome


ab chrom, telomere of each arm connect to other end

two breaks flip

2 copies of 1 arm, 0 of other
5 indications of karyotypeing
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
Genetic Screening (newborn)
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
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
Ashkenazi Jew
Tay achs, canavan disease, familial dysantonomia, cystic fibrosis
cystic fibrosis
african, african american, mediterranea
sickle cells anemai, betal thalassemia
south east asian
alpha thallsemia
controversy of CF screening
blanket screen, somewhat complex, CF varys among different pop. limitations of screen, most common mutations
negative test does not rule out.
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.
Prenatal screening

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)
Prenatal diagnosis--for karotyping

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
triple screen
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
indications for prenatal dx
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
Screening of NTDs
detailed US, level II US, fetal survey, use family history, carrier status
gene/environment NTDs
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.
Genetic symdrome
a pattern of malformations and features result form a single etiology. involve chromosome, dealtion of region, single gene mutation.