Genetic Testing

Question 1

What is teratogenesis

Answer 1

any substance capable of causing abnormal structural development in an embryo

Question 2

What are the three causes of congenital abnormalities

Answer 2

genetic factors, environmental factors, and multifactoral inheritance (traits caused by a combination of gene and environment)

Question 3

explain the sensitive period concept

Answer 3

some structures are only sensitive to teratogenic agents at a specific time. if something negative occurs around this time, the structure may be influenced

Question 4

what are the three categories of teratogenes

Answer 4

chemicals/drugs, maternal factors, physical agents

Question 5

What are examples of physical agent teratogenes?

Answer 5

radiation, extreme temperatures between 4-14 weeks, and mechanical factors like uterus anomalies, oligohydramnios, or amniotic bands

Question 6

2-3% of congential malformations are caused by…? What are possible effects?

Answer 6

drugs. severe malformation, mental challenges, growth restrictions

Question 7

What are some maternal factors that might impact fetal health

Answer 7

sickle cell, diabetes, infections

Question 8

what are the types of chromosomal abnormalities

Answer 8

single gene defects, abnormal number or structure of the chromosome

Question 9

How are autosomal dominant traits inherited

Answer 9

one parent affected, evident in every generation, 50% likely to pass trait to offspring

Question 10

How are autosomal recessive traits inherited

Answer 10

both parents affected, might skip a generation, 25% chance of passing trait with each pregnancy

Question 11

What is a karyotype

Answer 11

a visual map of a cell’s chromosomes, used to identify genetic disorders

Question 12

What is euploid

Answer 12

a normal balanced set of chromosomes, 23 pairs

Question 13

What is aneuploid

Answer 13

unbalanced set of chromosomes either too many or too few

Question 14

What is trisomy

Answer 14

the presence of an extra chromosome

Question 15

What is triploidy? how many chromosomes are there?

Answer 15

the presences of an additional set of chromosomes.. 69 chromosomes (46 normal + extra set of 23)

Question 16

What is a genotype

Answer 16

genetic make up of an individual

Question 17

What is a phenotype

Answer 17

the set of all observable characteristics, like eye color or behavior, resulting from genes and environment

Question 18

what genetic testing occurs in the first trimester between 11.5 and 13.5 weeks?

Answer 18

nuchal translucency and NIPT- maternal blood test for free or total beta-hCG and PAPP-A

Question 19

what is a nuchal translucency and how is it scanned?

Answer 19

measuring the fluid at the back of the neck in the end of the first trimester- inner to inner. >3mm may indicate trisomy 18 or 21. With normal genes, may indicate CHD

Question 20

What is cell-free fetal DNA testing or non-invasive prenatal testing and when is it performed

Answer 20

screening that indicates if a pregnancy is at risk for Trisomy 13, 18 or 21. performed after 10 weeks

Question 21

what is chorionic villus sampling (CVS) and how/when is it performed

Answer 21

cells are taken from the chorion and evaluated for chromosomal abnormalities. performed transvaginally between 9 and 12 weeks

Question 22

What is a quad screen and what markers are involved?

Answer 22

Biochemical screening to test for abnormalities. includes maternal serum afp (MSAFP), hCG, unconjugated estriol (ue3), and inhibin-A. these detect open neural tube defects (trisomy 21 and 18)

Question 23

what is abnormal MSAFP associated with?

Answer 23

incorrect dates, chromosome abnormalities, maternal fetal hemorrhage, fetal demise, other defects and tumors

Question 24

how do levels of hCG, uE3, and Inhibin-A typically appear with trisomy 21?

Answer 24

inhibin is elevated, hCG is elevated 2x the median value for normal, uE3 is lower than normal

Question 25

when might amniocentesis be recommended?

Answer 25

if sonography cannot determine the cause of multiple abnormal markers.

Question 26

What is amniocentesis and when is it performed?

Answer 26

US guided procedure that removes some anmiotic fluid for testing. typically only performed around 16 weeks

Question 27

Who is most affected by X-linked recessive traits? Why

Answer 27

men, they only have one x chromosome so if they inherit the disease they're more likely to express the trait. Women are often carriers instead of affected, since they must inherit two copies of the gene to express the trait.

Question 28

Who is most affected by X-linked dominant traits? Why

Answer 28

Both. Females have two X chromosomes, so a mutation in one will usually cause the condition. Males have one X so if the single X chromosome carries the mutation, the male will be affected

Question 29

What are some sonographic markers of genetic disorders

Answer 29

thickened nuchal fold, short femur or humerus

Question 30

What is an extrinsic cause of deformation?

Answer 30

oligohydramnios with amniotic bands causing disruptions

Question 31

What is an intrinsic cause of deformation?

Answer 31

oligohydraminos due to renal agenesis

Question 32

what is a syndrome

Answer 32

multiple abnormalities with a common cause. ex. down syndrome being caused by extra copies of chromosome 21

Question 33

what is VACTERL

Answer 33

vertebral, anal, cardiac, tracheoesophageal fistula, esophageal, renal, and limb abnormalities

Question 34

when would multiple anomalies be associated with one another?

Answer 34

if it is more common for them to happen togther than individually, but without a specific reason for this to occur

Question 35

Why is monosomy less common than trisomy?

Answer 35

it is generally incompatible with life