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Which chromosomes are acrocentric chromosomes?
13-15, 21, 22
What is at the end of every chromosome?
TTAGGG repeats 3-20 kb
What phase of the cell cycle takes up most of the day?
G1 (specific cell functions, 46 chromosomes, each chromosome has a single chromatid)
S phase
DNA synthesis, 2 chromatids/chromosome
When does cytokinesis occur?
telophase
Where does meiosis occur?
Gonadal tissue
Reduction division occurs when?
Meiosis I
When does recombination occur?
Meiosis II
Pachytene
homologous chromosomes align (bivalents- crossing over)
Is recombination more common males or females?
Females
Is recombination in the telomeres more common in males or females?
males
When does the egg arrest in meiosis I in the 4th month of fetal gestation?
dichtyatene, halfway through prophase
When does meiosis II finish in females?
fertilization
When does meiosis happen in males?
puberty
A mistake in nondisjuction in meiosis I causes...
uniparental heterodisomy
A mistake in nondisjunction in meiosis II causes.....
uniparental isodisomy
What percent of fertilized eggs have aneuploidy?
10-30%
What is the leading known cause of pregnancy loss (25%)?
aneuploidy
What is the leading known cause of mental retardation?
aneuploidy
What percent of liveborns are aneuploid?
0.3%
What percent of oocytes are aneuploid?
20-25%
What percent of sperm are aneuploid?
1-2%
What is the only common aneuploidy that is mostly paternal in error?
monosomy X (turner syndrome)
What aneuploidy is 45% male error and 55% female error?
XXY
true/false:  recombination is associated with trisomies
true
etiology of mosaicism
nondisjunction or anaphase lag
clinical findings in mosaicism
mild or variant form, streaks (lines of blaschko), asymmetry
What percent of trisomic rescue results in UPD?
1/3
situations that increase risk of UPD
1.  trisomy mosaicism
2.  presence of an extra marker or ring chromosome
3.  robertsonian translocation
4.  some recipricol translocations
mat UPD 7 accounts for.....
10% of russell silver syndrome
patUPD11
Beckwith Wiedemann syndrome
matUPD14
mild/moderate developmental delay, short stature, precocious puberty, scoliosis
patUPD14
polyhydramnios, low birth weight, blepharophimosis/short palpebral fissures, small ears, small thorax, abnormal ribs, joint contractures, severe mental retardation
matUPD15
prader willi, mosaicism found in some patients
patUPD15
angelman syndrome, fewer cases than matUPD15
matUPD20
growth retardation
matUPD2
few cases, IUGR, oligohydramnios, pulmonary hypoplasia, confined placental mosaicism
patUPD6
transient neonatal diabetes, low birth weight
mat UPD16
IUGR with normal development, imperferate anus, heart disease
what percent of recognized pregancies are triploid?
1-3%
% of chromosomally abnormal spontaneous abortions are triploid
15-20%
% of all spontaneous abortions that are triploid?
6%
% of liveborns that are triploid?
less than 1/20,000
Which triploidy is most viable?  Which is least viable?
69 XXY, 69XYY
% of triploidy that are diandric
85%
% of triploidy that are digynic
15%
phenotype of diandric triploid
well grown fetus with slightly small head size with partial hydadidiform mole, large cystic placenta, usually do not survive to term
phenotype of digynic triploid
growth retarded, placenta small and fibrotic, large head, can survive to term, longest survival 1 year
features common to triploidy
3-4 syndactyly, incomplete ossification of the skull, other anomalies
ovarian teratoma
46,XX all maternal material, caused by abnormal development or primary oocyte
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