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MCBM > Chromosomal Defects > Flashcards

Chromosomal Defects Flashcards

1
Q

About a 1/3 of congential defects are:

A

heart defects

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2
Q

hCG is coming from:

A

syncio something

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3
Q

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

A

maternal serum screen at 15-20 weeks of gestation

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4
Q

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

A

low; low; high

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5
Q

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

A

low; low low

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6
Q

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

A

high; normal; normal

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7
Q

____ is a structural defect of any type

A

anomaly

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8
Q

_____ is intrinsic and related to a genetic disorder

A

malformation

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9
Q

____ is extrinsic and is related to a mechanical disorder

A

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

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10
Q

___ is extrnsic and related to teratogen exposure

A

disruption

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11
Q

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

A

syndrome; marfan

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12
Q

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

A

sequence; low amniotic fluid

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13
Q

what are ex of multifactorial disorders

A

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

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14
Q

What is the eqn for heritability

A 
G/G+B+E =G/V
G=genetic
B= familial env
E= random env
V= total variance
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15
Q

what are features of multifactorial disorders

A
  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
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16
Q

what doesn’t close properly in spina bifida

A

rostral/caudal neuropore; due to lack of folate

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17
Q

what are some dev defects that can contribute to multifactorial disorders

A
  1. congenital heart defects
  2. spina bifida
  3. anencephaly (rostral neuropore not closing properly)
  4. cleft palate (palatine shelves not fusing properly)
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18
Q

what things contribute to most birth defects that we see

A
  1. alcohol
  2. tobacco
  3. retinoic acid (Vit A excess)
  4. dilantin (anti seizure drug)
  5. decrease in folate
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19
Q

what are features of whole chromosomal disorders

A
  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
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20
Q

What is XO abnormality

A

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

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21
Q

what is the trend seen in autosomal abnormalities

A

incidence goes down with severity of disease

Triplet embryo is a live birth via polyspermy

22
Q

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

A
  1. Klinefelter: XXY
  2. XYY: supermale; usually tall, some autism
  3. XXX : superfemale
23
Q

Usually see a trisomy at which chromosomes

A

13, 18, 21 (gene dosage affect)

24
Q

what is the most common trisomy in aborted fetuses

A

trisomy 16

25
Q

What are 2 ways you can get nondisjunction

A

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.

26
Q

What are some things that are obvious in uniparental disomy

A
  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.
27
Q

what are characteristics of Klinefelter syndrome

A
  1. tall
  2. low IQ
  3. infertile
  4. hypogonadism
  5. gynecomastia
28
Q

what are characteristics of tuner syndrome

A
  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
29
Q

what is fragile X syndrome:

A

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

30
Q

what are the three autosomal aneuploidies:

A

Trisomies:

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

31
Q

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

A

normal

32
Q

What are clinical features of trisomy 21

A
  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
33
Q

what are clinical features of trisomy 18 (edward)

A
  1. mental retardation
  2. rocker bottom feet
  3. malformed ears
  4. hypoplastic nails
  5. rarely survive past infancy
34
Q

what are clinical features of trisomy 13:

A
  1. lethal by 6 mo
  2. severe CNS malformations
  3. cleft lip/palate
  4. holoprosencephaly
35
Q

what are structural abnormalities

A
  1. deletions;
  2. Duplications
  3. Inversions; deliterious if breakpoint is within a gene
  4. Translocations
36
Q

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

A

chromosomal breaks;

  1. Cri du chat
  2. Prader Willi/Angelman
37
Q

what are clinical features of cri du chat syndrome

A
  1. 5 p deletion
  2. microcephaly
  3. micrognathia
  4. hypertelorism
  5. malformed ears
  6. severe retardation
38
Q

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

Abl

39
Q

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

A

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

40
Q

what are teratogens

A

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

41
Q

what factors affect the outcome of teratogen exposure

A
  1. time of exposure (the earlier exposed, the worst)
  2. dosage
  3. fetal/maternal genotype.
42
Q

what are ex of some teratogens

A
  1. thalidomide
  2. retinoic acid (accutane)
  3. alcohol
  4. hydantoin (dilantin)
43
Q

What are ex of other teratogens

A
  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
44
Q

week___ is most crucial for dev

A

3-8

45
Q

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

A
  1. meckels and richords (make bones of ear)
46
Q

What does maternal vit A deficiency lead to

A
  1. small eyes (micropthalmia)
  2. cleft palate/lip
  3. cardiovascular
  4. urogenital anomolies
  5. malformed limbs
47
Q

what does fetal alcohol syndrome lead to

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

1 in 6 have cleft palates

48
Q

what are features of fetal hydantoin sydrome

A
  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
49
Q

what does TORCH stand for

A
  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
50
Q

what are maternal preexisting conditions that can cause defects in infants

A
  1. diabetes mellitus: CV defects, CNS defects

2. Phenylketonuria: microcephaly, congenital heart defects, retardation

MCBM (59 decks)

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