Genetics Flashcards
What is the baseline risk for birth defects?
4% (1 in 25)
Birth defect due to INTRINSIC abnormalities, such as genetics; examples are Polydactyly and Cleft Lip; during embryonic period
Malformation
Birth defect due to EXTRINSIC factors that physically impinge on the fetus during development; examples are joint contractures and arhtrogyrposis (joint hooking); after embryonic period
Deformation
Birth defect caused by alteration of cellular constitution or tissue organization
Dysplasia
Birth defect due to the destruction of irreplaceable normal fetal tissue; usually due to amniotic bands and amputations
Disruption
Cascade of events from a single primary cause; example is Potter Sequence (renal agenesis–> oligohydramnios–> pulmonary hypoplasia and limb anomalies)
Sequence
Organogenesis is usually done by week…
Week 8 (embryonic period)
Examples of Chemical Teratogens
Alcohol Nicotine Tetracyclines Retinoic acid (Vit A) Thalidomide
Which teratogen can result in yellow staining of teeth and diminished growth of long bones
Tetracyclines
*STUDY AID: “Teethracyclines”
Which teratogen can result in growth deficiency, intellectual disability, congenital heart defects and abnormal facial features (smooth philtrum, thin vermillion border, etc.)
Alcohol
Examples of TORCHeS infections
Toxoplasmosis gondii Other (Parvo and Varicella) Rubella CMV HSV Syphilis
Obstetric/Fetal risks of Maternal Diabetes
Macrosomia Caudal regression syndrome (legs) Cardiac defects neonatal hypoglycemia (hyperplasia of fetal islet cells) Polycythemia
How can Ehlers-Danlos Syndrome complicate pregnancies
Mutations in Type III collagen
Worsening symptoms
Rapid onset labor
Uterine rupture
Arterial dissection/rupture
How can Marfan Syndrome complicate pregnancies
Valvular/Aortic complications
*HIGH risk
Signs/Symptoms of Down Syndrome
- Flat facies
- Duodenal Atresia
- Broad nasal bridge
- Low-set ears
Single palmar crease
Heart defects
Intellectual disability
Chromosome 18 trisomy; Death by age 1 year; small head and jaw, low-set ears, profound intellectual disability and heart defects; CLENCHING of hands and ROCKER BOTTOM feet
Edward Syndrome
Fancy name for Trisomy 18
Edward Syndrome
Signs/Symptoms of Trisomy 18 (Edward Syndrome)
- STUDY AID: “PRINCE” Edward
- Prominent occiput
- Rocker bottom feet
- Intellectual disability
- Nondisjunction
- Clenched hands
- low-set Ears
Chromosome 13 Trisomy; Death by age 1 year; intellectual disability, polydactyly, holoprosencephaly and cleft lip/palate
Patau Syndrome
Signs/Symptoms of Patau Syndrome (Trisomy 13)
- STUDY AID: “P” atau syndrome
- Polydactyly
- cleft liP/Palate
- holoProsencephaly (failure of forehead development)
- cutis aPlasia (absence of skin in 정수리)
Genotype for Klinefelter syndrome
47 XXY
Genotype for Turner Syndrome
45 XO
Aneuploidy (having missing or extra chromosomes) pathologies that are best diagnosed through ultrasound
Trisomy 18 (Edward's syndrome) Trisomy 13 (Patau Syndrome)
Females with the genotype 45 XO; short stature; WEBBED neck, “shield-like” chest, COARCATION of aorta and Renal malformations
Turner Syndrome
Signs/Symptoms of Turner Syndrome
Short stature Webbed neck Broad "shield-like" chest Coarctation of Aorta (narrowing of a short section of aorta) horseshoe kidney
Examples of Prenatal Diagnostic Testing and Screening
Chorionic Villus sampling
Amniocentesis
Multiple Marker Screening (cfDNA)
Genetic/Carrier Screening
When is Chorionic Villus Sampling done
10-14 weeks
Limitation of Chorionic Villus Sampling
Can’t test for open neural tube defects
When is Amniocentesis performed?
> 15 weeks
(Chorionic Villus Sampling/Amniocentesis) can test for open neural tube defects
Amniocentesis
Proportion of unaffected individuals with a negative result; “TRUE” negatives
Specificity
Proportion of AFFECTED individuals with POSITIVE result; “TRUE” positives
Sensitivity
What proteins does the “Quad screening” look for
AFP
hCG
DIA (Inhibin A)
uE3 (estriol)
What are the Quad Screening values for Down Syndrome (AFP, uE3, Inhibin and hCG)
Low AFP
Low uE3
High hCG
High Inhibin
Serum protein marker; synthesized in the yolk sac, GI tract and liver of fetus; can indicate Multiple Gestations, Cystic Hygroma, Neural tube defects (Spina bifida, Anencephaly), Abdominal Wall and GI defects
AFP (Alpha-fetoprotein)
What can cause an elevated AFP
Multiple gestations Spina bifida Anencephaly Abdomina Wall and GI defects Cystic Hygroma
Serum protein marker; produced by synctiotrophoblasts; rapidly peaks around 8 weeks, then decreases
hCG (Human Chorionic Gonadotropin)
Serum protein marker; produced by placenta from precursors from fetal adrenal glands and liver; steadily inc. throughout preganncy; low levels can indicate Smith-Lemli-Optiz syndrome and Ichthyosis
uE3 (Estriol)
Low levels of uE3 can be indicative of what pathologies
Smith-Lemli-Opitz Syndrome
Ichthyosis (widespread and persistent thick, dry, “fish-scale” skin)
Serum protein marker; produced by gonads, corpus luteum and placenta; inhibits FSH
Inhibin A
Common conditions seen in Ashkenazi Jews
Tay Sacks Cystic Fibrosis Canavan disease Familial Dysautonomia Gaucher Disease
Mutation seen in Cystic Fibrosis
delta F508
Which Trinucleotide repeat is seen in Fragile X (elf looking kids)
CGG