Question 1

Which of the following anomalies can be attributed to a disturbance in tissue resorption?

Accepted Answer

C

Question 2

Anencephaly is associated with a deficiency of ____________ in the maternal diet.

Accepted Answer

Anencephaly, a neural tube defect, is associated with a deficiency of folic acid in the maternal diet. Folic acid supplementation before and during pregnancy can significantly reduce the incidence of anencephaly.

Question 3

What percentage of congenital malformations is due to unknown causes?

Accepted Answer

Approximately 50% of congenital malformations are due to unknown causes, highlighting the complexity and the need for further research in this area.

Question 4

Phocomelia results from exposure to which human teratogen?

Accepted Answer

Phocomelia is a rare congenital malformation that causes underdeveloped or absent limbs. This is usually caused by exposure to thalidomide in the first trimester of pregnancy.

Question 5

Folic acid deficiency is now thought to be a major cause of what class of malformations?

Accepted Answer

Folic acid deficiency is now known to be a major cause of neural tube defects, including spina bifida and anencephaly. Trisomies are caused by errors in chromosome separation during meiosis. Ambiguous genitalia may be caused by genetic abnormalities or exposure to certain medications during fetal development. Polyploidy refers to having three or more sets of chromosomes, which can cause developmental abnormalities, but this is not typically caused by folic acid deficiency. Duplications refer to extra copies of one or more genes within a chromosome, which can also cause developmental abnormalities but is not directly related to folic acid deficiency.

Question 6

Amniotic mesoderm is situated most closely to the _______________.

Accepted Answer

The answer of Amniotic mesoderm is situated most closely to...

Question 7

Which of the following pairs is correctly matched?

Accepted Answer

Pelvic kidney is a result of failure of the kidney to ascend from the pelvis to its normal position in the lumbar region, which is a migration issue.

Question 8

Which of the following is responsible for the largest percentage of congenital malformations?

Accepted Answer

Unknown factors are responsible for the largest percentage of congenital malformations. Despite advances in medical science, the specific causes of most congenital malformations remain unidentified, leading to classification under unknown factors.

Question 9

What was the earliest recognized cause of human birth defects?

Accepted Answer

Rubella, also known as German measles, was recognized as the earliest cause of human birth defects. In the 1940s and 1950s, before the availability of a vaccine, rubella infections in pregnant women were found to cause congenital rubella syndrome, resulting in a range of birth defects including deafness, blindness, heart defects, and intellectual disabilities.

Question 10

Phocomelia is most likely to be seen after maternal exposure to which of the following teratogenic agents during the first trimester of pregnancy?

Accepted Answer

Phocomelia is a type of limb malformation that is commonly associated with thalidomide exposure during the first trimester of pregnancy. Thalidomide was a drug that was prescribed to pregnant women during the 1950s and 1960s to alleviate morning sickness. However, it was later discovered to be a potent teratogen that caused a range of birth defects, including phocomelia. Alcohol exposure during the first trimester can also cause a range of birth defects, but phocomelia is not commonly associated with alcohol exposure. Aminopterin, androgens, and ionizing radiation exposure can all cause birth defects, but phocomelia is not among the common effects associated with these agents.

Question 11

Administration of supplemental folic acid has markedly reduced the incidence of _______________.

Accepted Answer

Supplemental folic acid has been shown to greatly decrease the incidence of certain neural tube defects such as anencephaly, but it has not been shown to have any effect on Down syndrome or other chromosomal abnormalities, phocomelia, cyclopia or fetal alcohol syndrome.

Quiz 8: Developmental Disorders: Causes, mechanisms, and Patterns