MI 2.1 test

• genetic counselor helps navigate reproductive choices

• genetic testing

  • samples DNA and examines chromosomes/ genes for abnormalities

• single-gene disorders

  • caused by mutations in one gene

  • inherited in patterns

    • autosomal dominant

    • autosomal recessive

    • sex linked

  • genetic testing evaluates genotype to see if someone has disorder, will develop one, or is a carrier

• multifactorial disorders

  • caused by a combination of environmental factors + mutations in multiple genes

  • development of heart disease = associated w/ multiple genes

  • breast cancer is affected by genes found on chromosomes 6, 11, 13, 14, 15, 17, and 22

• chromosomal disorders

  • humans have 46 chromosomes (44 autosomes + 2 sex chromosomes)

  • diagnosed via karyotypes

• mitochondrial disorder

  • pretty rare

  • caused by mutations in nonchromosomal DNA of mitochondria

  • unique —> passed from mom to child

• Duchenne Muscular Dystrophy (DMD):

  • Genetic Type: X-linked recessive

  • Description: Progressive degeneration of muscle tissue due to a lack of dystrophin protein.

  • Symptoms: Muscle weakness, difficulty walking, respiratory problems.

  • Onset: Early childhood, typically diagnosed around age 3-5.

• Cystic Fibrosis (CF):

  • Genetic Type: Autosomal recessive

  • Description: Affects the respiratory, digestive, and reproductive systems, causing thick mucus production.

  • Symptoms: Persistent cough, respiratory infections, digestive issues.

  • Onset: Early childhood, diagnosed through newborn screening.

• Huntington's Disease (HD):

  • Genetic Type: Autosomal dominant

  • Description: Progressive neurodegenerative disorder affecting motor and cognitive functions.

  • Symptoms: Involuntary movements, emotional disturbances, cognitive decline.

  • Onset: Usually in adulthood, but can vary.

• Down Syndrome:

  • Genetic Type: Trisomy 21 (extra copy of chromosome 21)

  • Description: Intellectual disability and developmental delays due to an extra chromosome.

  • Symptoms: Intellectual impairment, distinct facial features, health issues (heart defects, thyroid problems).

  • Onset: Present from birth.

• Leber Hereditary Optic Neuropathy (LHON):

  • Genetic Type: Mitochondrial DNA mutation

  • Description: Affects the optic nerve, leading to sudden vision loss, usually in young adults.

  • Symptoms: Sudden, painless vision loss, usually in one eye initially.

  • Onset: Typically in the late teens or early adulthood.

• Alzheimer's Disease:

  • Genetic Type: Complex, involving genetic and environmental factors

  • Description: Progressive neurodegenerative disorder leading to memory loss and cognitive decline.

  • Symptoms: Memory loss, confusion, impaired reasoning.

  • Onset: Typically in later adulthood, but early-onset forms exist.

PCR

• selective amplification or specific genes

1. Denaturation:

• Process: Heat the DNA to around 94-98°C.

• Purpose: Separate the DNA double strands.

• Taq polymerase: Inactive at this high temperature.

2. Annealing:

• Process: Cool to 50-65°C.

• Purpose: Allow DNA primers to bind to specific target sequences.

• DNA primers: Short, single-stranded sequences that mark the start and end of the target region.

3. Extension (Elongation):

• Process: Temperature raised to 72°C.

• Purpose: Synthesize a new DNA strand complementary to the template.

• Taq polymerase: Activated at this temperature; adds DNA nucleotides (dNTPs) to the primer.

4. Amplification (Repeated Cycles):

• Process: Cycles of denaturation, annealing, and extension.

• Purpose: Exponentially increase the amount of DNA.

• Thermal cycler: Automated device controlling temperature cycles.

5. Final Extension:

• Process: Additional extension step at 70-75°C.

• Purpose: Ensure all remaining single-stranded DNA is fully extended.

• Taq polymerase: Continues to add dNTPs to complete synthesis.

6. Final Hold:

• Process: Hold at a lower temperature (e.g., 4-15°C).

• Purpose: Stabilize the amplified DNA.

• Result: Millions or billions of copies of the target DNA sequence.

Outcome:

• Purpose: Obtain a large quantity of the target DNA.

• Applications: Sequencing, cloning, diagnostic testing.

• Taq polymerase: Derived from a heat-resistant bacterium, essential for high-temperature PCR

• SNPs (single nucleotide polymorphisms)

  • parts of human genome that vary by just one nucleotide

  • if they occur in coding gene, lead to variation in traits or disease

  • change in DNA —> change in protein

first trimester screening

1. Blood Tests:

   • hCG (Human Chorionic Gonadotropin):

     • Purpose: Measurement of hCG levels in maternal blood.

     • Timing: Typically performed between the 10th and 13th weeks of pregnancy.

     • Significance: Abnormal levels may be associated with chromosomal abnormalities.

   • PAPP-A (Pregnancy-Associated Plasma Protein A):

     • Purpose: Measurement of PAPP-A levels in maternal blood.

     • Timing: Simultaneously with the hCG test.

     • Significance: Low levels may be associated with an increased risk of chromosomal abnormalities.

2. NT Ultrasound:

   • Timing: Performed between the 11th and 14th weeks of pregnancy.

   • Procedure: Measures the thickness of the fluid-filled space at the back of the fetal neck (nuchal translucency).

   • Significance: Increased NT thickness may indicate an elevated risk of chromosomal abnormalities.

3. Combined Risk Assessment:

   • Calculation: The results from the blood tests (hCG and PAPP-A) and NT ultrasound are combined with maternal age to calculate a comprehensive risk assessment.

   • Purpose: To identify pregnancies at a higher risk of chromosomal abnormalities.

4. Screening Results:

   • Low Risk: Most women receive results indicating a low risk.

   • Intermediate Risk: Some women may have intermediate-risk results, prompting further evaluation or diagnostic testing.

   • High Risk: A small percentage of women may receive results indicating a higher risk, leading to consideration of additional diagnostic tests for confirmation.

5. Advantages:

   • Early Detection: Provides information early in pregnancy.

   • Non-Invasive: First Trimester Screening is non-invasive, reducing the risk compared to invasive diagnostic tests.

6. Limitations:

   • False Positives/Negatives: Results may yield false-positive or false-negative findings.

   • Screening, not Diagnostic: It is a screening test, and positive results should be confirmed through more invasive diagnostic tests if necessary.

quad screen

1. Alpha-Fetoprotein (AFP):

   • Purpose: Measurement of AFP levels in maternal blood.

   • Timing: Typically performed between the 15th and 22nd weeks of pregnancy.

   • Significance:

     • Elevated AFP: Might indicate neural tube defects (e.g., spina bifida) or multiple pregnancies.

     • Low AFP: Might suggest a risk of chromosomal abnormalities.

2. Human Chorionic Gonadotropin (hCG):

   • Purpose: Measurement of hCG levels in maternal blood.

   • Timing: Simultaneously with the AFP test.

   • Significance:

     • Abnormal hCG levels, when combined with AFP, may indicate an increased risk of chromosomal abnormalities.

3. Unconjugated Estriol (uE3):

   • Purpose: Measurement of uE3 levels in maternal blood.

   • Timing: Performed concurrently with AFP and hCG tests.

   • Significance:

     • Low uE3 levels may be associated with an increased risk of chromosomal abnormalities.

4. Inhibin A (DIA - Dimeric Inhibin A):

   • Purpose: Measurement of DIA levels in maternal blood.

   • Timing: Simultaneously with AFP, hCG, and uE3 tests.

   • Significance:

     • Elevated DIA levels may be linked to an increased risk of chromosomal abnormalities, particularly Down syndrome.

5. Combined Risk Assessment:

   • Calculation: The levels of AFP, hCG, uE3, and DIA are analyzed together, along with other factors such as maternal age, to calculate a comprehensive risk assessment.

   • Purpose: Identify pregnancies at an increased risk of chromosomal abnormalities and neural tube defects.

6. Screening Results:

   • Low Risk: Most women receive results indicating a low risk.

   • Intermediate Risk: Some women may have intermediate-risk results, prompting further evaluation or diagnostic testing.

   • High Risk: A small percentage of women may receive results indicating a higher risk, leading to consideration of additional diagnostic tests for confirmation.

7. Advantages:

   • Non-Invasive: The Quad Screen is a non-invasive screening test.

   • Comprehensive: It provides information about multiple markers, enhancing its ability to detect potential issues.

8. Limitations:

   • False Positives/Negatives: Results may yield false-positive or false-negative findings.

   • Screening, not Diagnostic: Positive results should be confirmed through more invasive diagnostic tests if necessary.

NT ultrasound
Timing:

• Typically performed between the 11th and 14th weeks of pregnancy.

1. Procedure:

   • Ultrasound Examination: A trained sonographer uses ultrasound to measure the thickness of the clear space at the back of the fetal neck.

   • Fetal Position: The measurement is most accurate when the fetus is in a specific position, typically lying on its back.

2. Nuchal Translucency Measurement:

   • Normal Range: In a healthy pregnancy, the NT measurement is within a certain normal range.

   • Increased NT Thickness: An increased measurement may be associated with an elevated risk of chromosomal abnormalities, particularly Down syndrome (Trisomy 21) and Edwards syndrome (Trisomy 18).

3. Biomarker for Chromosomal Abnormalities:

   • Association with Down Syndrome and Trisomy 18: Increased NT thickness is often associated with an increased risk of these chromosomal abnormalities.

   • Other Chromosomal Conditions: It may also be associated with other chromosomal conditions and certain genetic syndromes.

4. Combined with Blood Tests:

   • Integrated Screen: The NT ultrasound is often combined with blood tests (such as the First Trimester Screen or Quad Screen) for a more comprehensive assessment.

   • Enhanced Accuracy: Combining NT measurements with blood test results enhances the accuracy of identifying pregnancies at risk for chromosomal abnormalities.

5. Advantages:

   • Early Detection: Provides information early in pregnancy.

   • Non-Invasive: The NT ultrasound is a non-invasive procedure, posing no risk to the fetus.

   • High Sensitivity: It has a relatively high sensitivity for detecting chromosomal abnormalities.

6. Limitations:

   • False Positives/Negatives: NT measurements alone may yield false-positive or false-negative results.

   • Screening, not Diagnostic: Positive results should be confirmed through more invasive diagnostic tests if necessary.

7. Follow-Up Testing:

   • Confirmation: If the NT ultrasound indicates an increased risk, further diagnostic tests such as chorionic villus sampling (CVS) or amniocentesis may be recommended for confirmation.

Anatomy ultrasound

1. Timing:

   • Typically performed between 18 and 22 weeks of pregnancy, although it can be done earlier or later if necessary.

2. Purpose:

   • Comprehensive examination of the fetus's anatomy and organ development.

   • Detection of any structural abnormalities or anomalies.

3. Components of the Examination:

   • Head and Brain:

     • Evaluation of the brain structure, ventricles, and presence of the corpus callosum.

   • Face:

     • Examination of facial features, including the nose, lips, and palate.

   • Spine:

     • Assessment of the spine for proper alignment and the presence of any abnormalities.

   • Heart:

     • Detailed examination of the heart chambers, valves, and major blood vessels.

   • Abdomen:

     • Inspection of abdominal organs, such as the stomach, liver, kidneys, and bladder.

   • Limbs:

     • Evaluation of the arms and legs for proper development and any signs of abnormalities.

   • Genitalia:

     • Identification of the fetus's sex and examination of the genitalia.

   • Placenta and Amniotic Fluid:

     • Assessment of the location and health of the placenta and the volume of amniotic fluid.

4. Gender Reveal:

   • Optional: Parents may choose to learn the baby's gender during the anatomy ultrasound.

   • Accuracy: The accuracy of gender determination is influenced by the fetus's position and the expertise of the sonographer.

5. Detection of Abnormalities:

   • Structural Anomalies: The ultrasound is particularly effective in identifying structural abnormalities, but not all conditions can be detected.

   • Chromosomal Abnormalities: Some structural anomalies may be indicative of chromosomal conditions, but additional tests may be needed for confirmation.

6. Advantages:

   • Detailed Information: Provides a detailed overview of fetal anatomy.

   • Non-Invasive: An ultrasound is a non-invasive procedure, posing no risk to the fetus.

   • Early Detection: Can identify many structural anomalies early in pregnancy.

7. Limitations:

   • Complete Assurance: While it can detect many abnormalities, it cannot guarantee the absence of all potential issues.

   • Timing: Some anomalies may not be apparent until later in pregnancy.

8. Follow-Up or Additional Testing:

   • Diagnostic Tests: If abnormalities or concerns are identified, additional diagnostic tests, such as amniocentesis or chorionic villus sampling, may be recommended for confirmation.

cell-free fetal DNA analysis
Source of DNA:

• Origin: Fetal DNA is released into the maternal bloodstream through various biological processes, such as apoptosis of fetal cells.

1. Timing:

   • When Performed: Typically performed after 9 weeks of gestation.

   • Frequency: Generally offered as part of prenatal screening for chromosomal abnormalities.

2. Conditions Screened:

   • Chromosomal Abnormalities: NIPT primarily screens for common chromosomal conditions such as Down syndrome (Trisomy 21), Edwards syndrome (Trisomy 18), and Patau syndrome (Trisomy 13).

   • Sex Chromosome Abnormalities: Some NIPT tests also provide information about sex chromosome conditions.

3. Procedure:

   • Blood Sample: A maternal blood sample is collected.

   • Isolation of DNA: Fetal DNA is isolated from the maternal blood sample.

   • Analysis: High-throughput sequencing technologies are used to analyze the fetal DNA for chromosomal abnormalities.

4. Advantages:

   • Non-Invasive: No risk of miscarriage associated with invasive procedures (such as amniocentesis or chorionic villus sampling).

   • High Sensitivity and Specificity: NIPT has high accuracy for detecting common chromosomal abnormalities.

   • Early Detection: Can be performed early in pregnancy.

5. Limitations:

   • Not Diagnostic: NIPT is a screening test, and positive results should be confirmed through invasive diagnostic tests.

   • Limited Scope: Primarily screens for specific chromosomal abnormalities and may not provide information about other genetic conditions or structural anomalies.

   • False Positives/Negatives: While highly accurate, false-positive or false-negative results may occur.

6. Results:

   • Reported as Probability: Results are typically reported as a probability or likelihood of the fetus having a specific chromosomal abnormality.

   • Counseling: Genetic counseling is often recommended to discuss results and potential implications.

7. Follow-Up Testing:

   • Confirmation: Positive results may be followed by diagnostic tests such as chorionic villus sampling (CVS) or amniocentesis for confirmation.

8. Cost and Accessibility:

   • Cost: NIPT can be more expensive than traditional screening methods.

   • Accessibility: Availability may vary depending on geographic location and healthcare provider.

chorionic villus sampling

1. Timing:

   • When Performed: Typically performed between the 10th and 13th weeks of pregnancy.

2. Indications:

   • High-Risk Pregnancies: Recommended for pregnancies identified as high risk for chromosomal abnormalities through other screening tests.

   • Genetic Disorders: Used to diagnose specific genetic conditions when there is a family history or parental carrier status.

3. Procedure:

   • Method: There are two main methods:

     • Transabdominal (Most Common): A thin needle is inserted through the abdominal wall to reach the chorionic villi.

     • Transcervical: A catheter is passed through the cervix to obtain a sample.

4. Sample Collection:

   • Chorionic Villi: Small tissue samples are collected from the placenta.

   • Genetic Material: The collected samples contain genetic material from the fetus.

5. Analysis:

   • Chromosome Analysis: The collected tissue is analyzed for chromosomal abnormalities, including Down syndrome (Trisomy 21), Edwards syndrome (Trisomy 18), and Patau syndrome (Trisomy 13).

   • Genetic Disorders: CVS can also be used to diagnose specific genetic disorders based on the parents' carrier status.

6. Advantages:

   • Early Diagnosis: Can provide earlier results compared to some other diagnostic tests.

   • High Diagnostic Accuracy: CVS has high accuracy in diagnosing chromosomal abnormalities and genetic disorders.

7. Limitations:

   • Risk of Miscarriage: While rare, there is a small risk of miscarriage associated with the procedure.

   • Cannot Detect Neural Tube Defects: Unlike some other tests, CVS does not provide information about neural tube defects.

8. Results:

   • Confirmed Diagnoses: Positive results are considered a confirmed diagnosis.

   • Counseling: Genetic counseling is often recommended to discuss results and potential implications.

9. Follow-Up Testing:

   • Confirmation: CVS results are considered highly accurate, but in some cases, additional testing may be recommended for confirmation.

amniocentesis

1. Timing:

   • When Performed: Typically performed between the 15th and 20th weeks of pregnancy.

2. Indications:

   • High-Risk Pregnancies: Recommended for pregnancies identified as high risk for chromosomal abnormalities through other screening tests.

   • Genetic Disorders: Used to diagnose specific genetic conditions when there is a family history or parental carrier status.

3. Procedure:

   • Needle Insertion: A thin, hollow needle is inserted through the abdominal wall and into the amniotic sac.

   • Ultrasound Guidance: The procedure is usually guided by ultrasound to ensure proper placement and avoid harm to the fetus.

   • Sample Collection: A small amount of amniotic fluid is withdrawn into a syringe.

4. Sample Composition:

   • Amniotic Fluid: The collected fluid contains fetal cells, which include skin cells, urine, and other cellular components.

5. Analysis:

   • Chromosome Analysis: The collected cells are analyzed for chromosomal abnormalities, such as Down syndrome (Trisomy 21), Edwards syndrome (Trisomy 18), and Patau syndrome (Trisomy 13).

   • Genetic Disorders: Amniocentesis can also be used to diagnose specific genetic disorders based on the parents' carrier status.

6. Advantages:

   • Definitive Diagnosis: Results from amniocentesis are considered definitive.

   • High Diagnostic Accuracy: Amniocentesis has high accuracy in diagnosing chromosomal abnormalities and genetic disorders.

7. Limitations:

   • Risk of Miscarriage: While rare, there is a small risk of miscarriage associated with the procedure.

   • Cannot Detect Neural Tube Defects: Unlike some other tests, amniocentesis does not provide information about neural tube defects.

8. Results:

   • Confirmed Diagnoses: Positive results are considered a confirmed diagnosis.

   • Counseling: Genetic counseling is often recommended to discuss results and potential implications.

9. Follow-Up Testing:

   • Confirmation: Amniocentesis results are considered highly accurate, but in some cases, additional testing may be recommended for confirmation.