Congenital Defects and Teratogens (Lec 9)

Question 1

Congenital Defects

Answer 1

Refers to all inborn abnormalities (morphological or biochemical) at birth

Question 2

Causes of Congenital Defects

Answer 2

Environmental

• Infectious agents
• Chemical and Pharmacological
• Radiation

Genetic

• Chromosomal
• Monogenic

Question 3

Environmental Factors (Teratogens)

Answer 3

Teratogen: any agent that can harm an embryo or fetus

Question 4

Infectious Agents: Rubella

Answer 4

Causes severe effects in fetuses, Congenital Rubella Syndrome causes miscarriage or birth defects such as heart defects, deafness, brain damage, eye problems, mental retardation. Most dangerous during 1st trimester

Question 5

Infectious Agents: Toxoplasmosis

Answer 5

Zoonotic intracellular parasitic infection caused by eating undercooked/contaminated meats. Able to cross placenta and affect brain -> hydrocephalus, mental retardation. Induces miscarriage later in pregnancy

Question 6

Infectious Agents: Zika Virus

Answer 6

Transmitted through an infectious mosquito bite and has ability to be transferred from mother to fetus during pregnancy. Causes microcephaly and calcification of brain tissue

Question 7

Infectious Agents: Listeria

Answer 7

Listeria infection in newborns can cause miscarriage, stillbirth and severe illness in newborns. Caused by eating uncooked cheese, seafood.

Question 8

Infectious Agents: Salmonella

Answer 8

Salmonella bacteria can cause gastroenteritis or food poisoning. Caused by eating foods that contain uncooked or raw eggs or reheated chicken

Question 9

Chemical and Pharmacological Teratogens: Thalidomide

Answer 9

Given to women to prevent nausea and vomiting (morning sickness). Can cause Phocomelia (fetus with hands and feet developed and underdeveloped limbs), Ectromelia (total absense of limbs), and malformation of eyes, heart, ears, noses

Question 10

Chemical and Pharmacological Teratogens: Alcohol

Answer 10

Compromises function of placenta by crossing and adversely affecting fetal development. Fetal Alcohol Syndrome (FAS) can cause microcephaly, malformation of heart, limbs, joints and face, seizures, mental difficulty etc.

Question 11

Chemical and Pharmacological Teratogens: Cigarette Smoking

Answer 11

Causes cleft lip, abnormal lung function, miscarriage, low birth weight, ectopic pregnancy (implantation in uterine tube), sudden infant death syndrome

Question 12

Radiation

Answer 12

Causes death, mental retardation, CNS abnormalities (microcephaly etc.). Severity depends on stage of pregnancy and absorbed dose.

Question 13

Genetic Defects

Answer 13

A genetic problem causes by one or more abnormalities formed in the genome

Question 14

Chromosomal: Deletions

Answer 14

E.g. Cri Du Chat
Deletion of a small part of chromosome 5, children have severe mental impairment, small head with unusual facial features

Question 15

Chromosomal: Duplications

Answer 15

E.g. Fragile X Chromosome
Expansion of the CGG Trinucleotide repeat affecting the Fragile X retardation 1 (FMR1) gene on the X Chromosome. Most people have 29 repeats, Fragile X have >700 due to duplications

Question 16

Chromosomal: Translocations

Answer 16

E.g. Acute Myeloid Luekemia
Fragment of chromosome is translocated and causes rapid growth of poorly differentiated white blood cells that then accumulate in the bone marrow.

Question 17

Chromosomal: Inversions

Answer 17

E.g. Haemophilia A
Chromosome breaks in 2 places, the segment then flips and re-inserts. Does not involve loss or gain of genetic material but protein function may be affected