Genetics Chapter 15

Front 1

name the 4 methods of invasive prenatal testing

Back 1

1.) Amniocentesis
2.) Chorionic Villis Sampling
3.) Cordocentesis
4.) Preimplantation genetic diagnosis

Front 2

name the 4 methods of noninvasive prenatal testing

Back 2

1.) Maternal Serum alpha-fetoprotein
2.) First and Second trimester maternal serum screening
3.) Ultrasonography
4.) Isolation of fetal cells from maternal circulation

Front 3

What is the leading indication for prenatal diagnosis?

Back 3

Advanced age

Front 4

What is the generally accepted criterion for eligibility for prenatal diagnosis by amniocentesis or CVS?

Back 4

the chance of fetal abnormality is at least as great as the chance of miscarriage from the test

Front 5

What is the chief condition for which advanced age women are at risk for in their pregnancies?

Back 5

Down Syndrome.

Front 6

Why was age 35 chosen for testing?

Back 6

the odds of having an abnormal pregnancy are equal to the risk of testing miscarriage at this age.

Front 7

List the 7 principal indications for prenatal diagnosis by invasive testing

Back 7

1.) Advance maternal Age
2.) Previous child with de novo chormosomal aneuploidy
3.) Presence of structural chromosome abnormality in one of the parents
4.) Family history of a genetic disorder that may be diagnosed or ruled out by biochemical or DNA analysis
5.) Family history of an X-linked disorder for which there is no specific diagnostic test (sex screening)

6.) Risk of neural tube defect

7.) Abnormalities in Maternal Serum screening and ultrasound examinations

Front 8

What is an NTD?

Back 8

Neural Tube defect. A risk for this is a condition which allows for invasive prenatal testing.

Front 9

Amniocentesis

Back 9

inserting a needle into the amniotic sac and removing a sample of amniotic fluid transbdominally. ultrasounds are used before the procedure to ensure safety and efficiency of the test.

typically performed on the 15th and 16th week after the first day of the last menstrual period.

Front 10

alpha fetoprotein can be assayed to test for what condition

Back 10

open neural tube defects.

Front 11

what is alpha fetoprotein?

Back 11

a fetal glycoprotein produced mainly in the liver.secreted into the fetal circulation and excreted in the kidneys. It enters the maternal blood stream through the placenta so it is detectable both in maternal serum as well as amniocentesis.

Front 12

what technique is used to assay AFP (alpha detoprotein)

Back 12

immunoassay

Front 13

What are causes of elevated AFP besides NTDs?

Back 13

1.) Fetal blood contamination
2.) Fetal Death
3.) Twin Pregnancy
4.) Fetal abnormalities (omphalocele, congenital nephrosis, rare conditions)
5.) Unexplained variations
6.) false positive.

Front 14

midtrimester amniocentesis results in what risk of miscarriage.

Back 14

1/1600 above baseline. (baseline is 1-2% for all pregnancies.

Front 15

What is the congenital defect associated with early amniocentesus ( before week 13)?

Back 15

talipes equinovarus (Club feet)

Front 16

What is chorionic Villus sampling?

Back 16

bipopsy of tissue from the villous area of the chorion taken transcervically or transabdominally between the 10th and 12th week of pregnancy.

Front 17

what are chorionic villi

Back 17

proliferations of the cytotrophoblasts which contain mesenchymal cores containing capilaries

Front 18

What is an advantage of CVS over amniocentesis?

Back 18

tests can be conducted earlier. 10-12 weeks instead of 15-16 weeks.

Front 19

What are disadvantages of CVS.

Back 19

AFP screening cannot be conducted this can only be done 15-16 weeks after the start of pregnancy.

Front 20

what is the rate of ambiguity in CVS results. What is done about this.

Back 20

2% chance of ambiguity due to mosaicism or pseudomosaicism. Amniocentesis is always performed to confirm any results.

Front 21

what is MSAFP

Back 21

Maternal serum AFP test. It is a noninvasive test which detects unusally high levels of AFP. ultra sound can typically limit the possibilies to determine if it is a NTD.

Front 22

Define Sensitivity

Back 22

percentage of positives measured as positive

Front 23

Define Specificity

Back 23

percentage of positive results that are non false positives.

Front 24

What supplemental nutrient is found to decrease the risk of NTDs by 75%?

Back 24

Folic Acid

Front 25

Aside form NTDs (a 75% decrease in risk?) what is folic acid found to also help prevent.

Back 25

Orofacial clefting (cleft pallet) by 40%!

Front 26

what percentage of Down Syndrome babies are born to parents under 35?

Back 26

70%! but they are below the cutoff for invasive screening.

Front 27

What was found to be unique in maternal serium tests when the baby was later found to have down syndrome? What is flawed with this to make it unviable as a test itself?

Back 27

depressed MSAFP levels.

these levels overlapped too much with normal MSAFP levels (lacked statistical significance) low specificity.

Front 28

what two maternal serum substances are measured in first trimester screening (10-13 weeks)

Back 28

Pregnancy associated plasma protein A (PAPP-A)

Human chorionic gonadotropin (hCG)

Front 29

A patient with Down Syndrome would have what levels of PAPP-A and hCG in the maternal serum after 10 weeks?

Back 29

Low PAPP-A and high hCG

Front 30

how can trisomies be distinguished after 10 weeks?

Back 30

in the maternal serum test, PAPP-A is depressed for all trisomies, but in the case of trisomy 21, hCG levels are elevated. In all other trisomies, hCG levels are depressed.

Front 31

what is nuchal tranlucency?

Back 31

view on ultrasonograph which can be used to detect abnormal fluid buildup on the soft tissue of the neck.

Front 32

What 3 substances are measured during second trimester maternal serum analysis?

Back 32

MSAFP, B-hCG, and unconjugated estriol.

Front 33

what is the battery of tests performed on maternal serum in the second trimester know as?

Back 33

triple screen, because is measures MAAFP, B-hCG, and unconjugated estriol

Front 34

The quadruple screen, offered by some laboratories in the second trimester tests for what additional substance?

Back 34

inhibin A

Front 35

how does Inhibin A reflect chromosomal abnormalities?

Back 35

it is elevated in trisomy 21, but unaffected in all other trisomies.

Front 36

how does unconjugated estriol reflect chromosomal abnormality?

Back 36

it is depressed in all trisomies

Front 37

low levels of of unconjugated estradiol can indicate what? what about severely low levels?

Back 37

Smoking mother, fetal immaturity, trisomy.

extremely low levels may indicate steroid sulfatse deficiency or the Smith Lemli Opitz syndrome

Front 38

What prenatal screen can indicate the presence of Smith Lamli Opitz syndrome?

Back 38

the triple screen performed on maternal serum during the second trimester. PArticularly the assay on unconjugated estradiol levels. If very low, Smith lamli opitz or low steroid sulfatase levels will be possible.

Front 39

What bone i missing on an ultra sound in 75% of patients with down syndrome?

Back 39

the nasal bone.

Front 40

name three conditions which supplemental vaginal ultrasonography is used to detect beyond the tradition abdominal method

Back 40

anencephaly, meningomyelocele, and cystic hygroma.

Front 41

numerous abnormalities is a sign of what condition?

Back 41

chromosomal abnormalities.

Front 42

what is Holt Oram Syndroms?

Back 42

autosomal dominant disorder categorized by congenital heart disease in association with hand abnormalities

Front 43

Osteogenesis imperfecta type II is usually inherited how?

Back 43

new dominant mutation, with 6% recurrence risk due to germline mosaicism. 5% of families transmit is as an autosomal recessive disorder with a 25% recurrence risk.

Front 44

Name the single gene diorders which are diagnosed or ruled out by ultrasonography (4)

Back 44

1.) Holoprosencephaly
2.) Infantile polycystic kidney disease
3.) Meckel-Gruber syndrome
4.) Fryns Syndrome

F Him

Front 45

name the mutifactorial disorders that can be diagnosed or ruled out by ultrasonography. (4)

Back 45

1.) Cleft lip or other facial issues
2.) Club Foot
3.) Congenital heart defects
4.) Neural Tube defects

N triple C

Front 46

name the abnormalities identifiable on an untrasound that may iindicate the presence of a syndrome (5)

Back 46

1.) abnormal genitalia
2.) cystic hygroma
3.) polydactyly
4.) Omphalocele
5.) Radial Ray Disease

ORCA Pussy

Front 47

at which stage of gestation is fetal sex determination possible on an ultrasound?

Back 47

15 weeks

Front 48

define cordocentesis

Back 48

insertion of a needle into the umbilical vessel to draw a blood sample.

Front 49

karyotypes usually find what in conjunction with most abnormalities in ultrasonographic findings?

Back 49

trisomies and structural chromosomal abnormalities.

Front 50

Mosaicism

Back 50

presence of two or more cell lines in an individual or tissue sample.

Front 51

True mosaicism

Back 51

multiplecolonies in multiple cultures

Front 52

pseudo mosaicism

Back 52

multiple colonies in only one cell

Front 53

what is a common reason for misidentified mosaicism?

Back 53

Maternal Contamination.

Front 54

Trisomy Rescue

Back 54

loss of an extra chromosome postzygotically

Front 55

Prader willi syndrome is caused by what chromosomal abnormality

Back 55

2 maternal copies of chromosome 15

Front 56

Angelman syndrome is caused by what chromosomal abnormality

Back 56

2 paternal copies of chromosome 15

Front 57

what conditions have the highest treatment success rates prenatally? Why?

Back 57

metabolic disorders. because maternal treatment can many times help the baby. Example PKU.