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Flashcards in Chromosomal Defects Deck (50)
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About a 1/3 of congential defects are:

heart defects


hCG is coming from:

syncio something


what are non invasive tests that are performed routinely on pregnant women

maternal serum screen at 15-20 weeks of gestation


you have an inc risk of trisomy 21 if you have ___AFP, ____uE2 but ____hGC

low; low; high


you have an inc risk of trisomy 18 if you have ____ AFP, ____uE2, and ____ hCG

low; low low


if you have an inc risk of neural tube defect than you will have ____ AFP, ____ u#2 and ____ hCG

high; normal; normal


____ is a structural defect of any type



_____ is intrinsic and related to a genetic disorder



____ is extrinsic and is related to a mechanical disorder

deformation; trauma or constraint (multiple fetuses, amniotic bands)


___ is extrnsic and related to teratogen exposure



____refers to multiple anomalies that occur independently, but are caused by a single defect

syndrome; marfan


_____is when a structural or mechanical factor leads to multiple secondary effects

sequence; low amniotic fluid


what are ex of multifactorial disorders

hypertension, cardiovascular disease, coronary artery disease, IDDM, some forms of cancer; combination of genetics + env factors that give you phenotypical expression


What is the eqn for heritability

G/G+B+E =G/V
B= familial env
E= random env
V= total variance


what are features of multifactorial disorders

1. disorders that run in families
2. no single gene/chromosomal abnormality is responsible
3. a comb of genetics and env factors req for phenotypic expression
4. dont follow mendelian patterns of inheritance


what doesn't close properly in spina bifida

rostral/caudal neuropore; due to lack of folate


what are some dev defects that can contribute to multifactorial disorders

1. congenital heart defects
2. spina bifida
3. anencephaly (rostral neuropore not closing properly)
4. cleft palate (palatine shelves not fusing properly)


what things contribute to most birth defects that we see

1. alcohol
2. tobacco
3. retinoic acid (Vit A excess)
3. dilantin (anti seizure drug)
4. decrease in folate


what are features of whole chromosomal disorders

1. incompatible with life (spontaneous abortion
2. rarely reproduce
3. most directly linked to maternal age
4. may occur in autosomes or sex chromosomes
5. detectable via karyotype analysis


What is XO abnormality

Turner syndrome: True monosomy (just one sex chromosome) not very harsh but see it at a 10 fold lower incidence


what is the trend seen in autosomal abnormalities

incidence goes down with severity of disease
Triplet embryo is a live birth via polyspermy


which sex chromosomal abnormalities are in newborns are about 1/1000

1. Klinefelter: XXY
2. XYY: supermale; usually tall, some autism
2. XXX : superfemale


Usually see a trisomy at which chromosomes

13, 18, 21 (gene dosage affect)


what is the most common trisomy in aborted fetuses

trisomy 16


What are 2 ways you can get nondisjunction

Meiosis 1: Tetrads dont disjoin properly so all 4 copies go to daughter cell and disjoin in next meiosis
Meiosis 2: sister chromatids dont disjoin in second meotic division and both go to 1 daughter cell.
-This event leads to uniparental disomy. In trisomy, during cleavae stages One chromosme will be lost in a div so daughter cell wont have an extra chromosme (normal dipoloid complement). every cell in this embryo that arises from this daughter cell is normal so you get mosaicism, where an embryo is derived from 2 genetically derived pop's of cells (one with normal diploid complement, one with trisomy) which influences severity of disease.


What are some things that are obvious in uniparental disomy

1. If this chromosome houses cystic fibrosis mutaiton and you have both copies from parent with mutation you can get disease without having two carrier parents.
2. IIf imprinted region and your meant to have a copy form mom and dad to compensate from each other you can get Prader Willi or Angelmans without having a deletion.


what are characteristics of Klinefelter syndrome

1. tall
2. low IQ
3. infertile
4. hypogonadism
5. gynecomastia


what are characteristics of tuner syndrome

1. short
2. infertile
3. issues with aorta
4. round moles
5. webbing around neck
6. underdev breast and nipples are really apart
7. no IQ issues
8. 25% mosaics


what is fragile X syndrome:

Major cause of mental retardation
1. Has extra GCC repeat in 5; UTR of FMRI gene
> 230 repeats = FMR1 silenced via methylation
2. macro orchidism
3. dental crowding


what are the three autosomal aneuploidies:

13: Patau
18: edward
21: down
*true autosomal monosomies are not found, they're lethal.


If mosaics, disease is not going to be as severe because they have a subpop of their bodies that are made up of _____ cells. 4% are translocations



What are clinical features of trisomy 21

1. hypotonia (not good body control)
2. mental retardation
3. epicanthic folds
4. simian creases
5. short stature
6. forrowed tongue
7. heart defects
8. predisposition for leukemia
9. brushfield spots on iris
10. gap between toe
11. neurofibrillary tangles
12. duodenal obstruction


what are clinical features of trisomy 18 (edward)

1. mental retardation
2. rocker bottom feet
3. malformed ears
4. hypoplastic nails
5. rarely survive past infancy


what are clinical features of trisomy 13:

1. lethal by 6 mo
2. severe CNS malformations
3. cleft lip/palate
4. holoprosencephaly


what are structural abnormalities

1. deletions;
2. Duplications
3. Inversions; deliterious if breakpoint is within a gene
4. Translocations


What are ex of deletions (partial monosomies) and what are they caused by

chromosomal breaks;
1. Cri du chat
2. Prader Willi/Angelman


what are clinical features of cri du chat syndrome

1. 5 p deletion
2. microcephaly
3. micrognathia
4. hypertelorism
5. malformed ears
6. severe retardation


translocation bet chromosomes 9 and 22 produce a fusion gene comprised of the ____ oncogene and 5' portion of the Bcr gene and results in a fusion protein that contributes to dev of chronic myeloid leukemia



A robertsonian translocation is between two ___ chromosomes and is associated with a familial form of Down sydrome

acrocentric; the centromere is very near the end of a chromosme


what are teratogens

drugs/chemicals/infectious agents that may adversely affect fetal dev.


what factors affect the outcome of teratogen exposure

1. time of exposure (the earlier exposed, the worst)
2. dosage
3. fetal/maternal genotype.


what are ex of some teratogens

1. thalidomide
2. retinoic acid (accutane)
3. alcohol
4. hydantoin (dilantin)


What are ex of other teratogens

1. ACE inhibitors (for BP): kidney defects in 2, 3 trimester
2. antineoplastic agents; severe
3. mercury: neurotoxin, cerebral palsy like syndrome
4. Warfarin (clotting agent), lithium, tobacco
5. lack of morphogen: folate; critical for neural tube dev


week___ is most crucial for dev



what kind of cartilage do you get from 1st and 2nd pharyngeal arch?

1. meckels and richords (make bones of ear)


What does maternal vit A deficiency lead to

1. small eyes (micropthalmia)
2. cleft palate/lip
3. cardiovascular
4. urogenital anomolies
5.malformed limbs


what does fetal alcohol syndrome lead to

1. mental retardation
2. skeletal defects
3. growth retardation
4. heart defects
.5 smooth philtrum

1 in 6 have cleft palates


what are features of fetal hydantoin sydrome

1. craniofacial anomalies
2. growth retardation
3. mental retardation
4. limb defects
* degree of severity is linked to low activity form of epoxide hydrolase ( enzyme in liver that metabolizes this drug) in mother


what does TORCH stand for

1. toxoplasmosis: parasite found in cats, can get hydrocephalus
2. other: HIV, Syphillis (bacteria), VZV (chicken pox)
3. rubella: german measles (blindness, cataracts)
4. CMV: benign infection in adult that can have horrible issues in dev fetus
5. HSV: herpes virus that doesnt cross fetal membrane but if infection, baby can acquire it


what are maternal preexisting conditions that can cause defects in infants

1. diabetes mellitus: CV defects, CNS defects
2. Phenylketonuria: microcephaly, congenital heart defects, retardation