1. d. Ante- natal and post-natal screening
What do you know?
What is ante-natal screening?
How is it done
Why is it done?
What is post-natal screening?
How is it done?
What is a pedigree chart and why are they made?

2. Screening A variety of techniques
Monitors health of mother and developing fetus
Before birth (ante-natal)
After the birth (post-natal)

3. Ante-natal screening Identifies risk to mother and baby
Further tests can be given
Tests can be physical or chemical
Ultrasound
Blood pressure
Blood typing
Blood chemical analysis
Urine analysis
Cell chemical analysis
Karyotype analysis
Rhesus antibody testing

4. Ultrasound imaging Scanner High frequency sounds reflect from foetus
Image produced
8 – 12 weeks for dating scan (baby due date)
18 – 20 weeks anomaly scan (serious physical abnormalities)

5. Biochemical tests Blood and urine analysis
Chemical levels indicate normal development at specific times
Human gonadotrophin (HCG) used in pregnancy tests. It increases following implantation.
16 – 18 weeks test for 3 markers offered.
Pre-eclampsia in association with high blood pressure, excessive protein in blood plasma, high levels of urea, lower levels of calcium.
Tests are looking for normal changes at right time.

6. False positive or false negative results
Biochemical changes are normal in pregnancy
Tests can show raised or lowered levels
Analysis of tests need to account for false positives and false negatives
False positives seen if a marker is measured at wrong time and it leads to a positive diagnosis when there isn’t one
False negatives seen if marker is measured found to be low but is expected to be low normally
Careful analysis and timing of tests is needed

7. Screening or diagnostic testing
Screening tests are used to detect signs and symptoms that may be associated with conditions or disorders.
Diagnostic tests give a definitive result that an individual is suffering from a condition or disorder

8. Amniocentesis
14 – 16 weeks
Amniotic fluid extracted contains foetal cells
Cell chromosomes analysed in karyotype
Takes about 2 weeks
Can detect chromosome abnormalities i.e. extra

9. Chorionic villus sampling (CVS)
Placental cells extracted via reproductive tract
From 8 weeks
Earlier means earlier decisions
Causes more miscarriages than amniocentesis

10. Karyotype
Arrangement of analysed chromosomes into homologous pairs.

11. Down’s syndrome karyotype

12. Turner’s syndrome karyotype
An X missing in females, short, ovaries not developed,
no secondary sexual characteristics at puberty

13. Klinefelter’s syndrome karyotype
Extra X in males, male sex organs, infertile, very few sperm

14. Edward’s syndrome karyotype
Extra 18 chromosome, skull shape unusual, small chin,
heart and kidney malfunction, 1st year survival

15. Rhesus antibody testing
Rhesus antigens (antigen D) found on RBC
Rhesus positive have antigen
Rhesus negative people produce anti – D antibodies
Rhesus negative mother pregnant with rhesus positive foetus could produce antibodies if cells come into contact with foetal blood at birth
Rhesus negative mother given anti Rhesus antibodies to destroy Rhesus antigens left behind before immune system responds

16. Post – natal screening Few genetic inherited disorders can be treated
Phenylketonuria (PKU) is one that can
All babies tested for PKU
Blood test for excess phenylalanine (amino acid)
Restricted diet is needed if PKU diagnosed
Person cannot metabolise phenylalanine as normal
Other examples include
Galactosaemia – treated with restricted diet
Hypothyroidism – no thyroxine produced injections given

17. Inheritance pedigrees
Studied by looking at family histories of disorders
Patterns analysed and pedigree charts produced to trace disorders through inheritance
Can aid counselling and decision making process

18. Revising Inheritance Alleles Homozygous Heterozygous Dominant
Recessive
Genetic crosses
Phenotype
Genotype
Ratios
Punnet square

25. Incomplete dominance
Incomplete dominance or co-dominance occurs in some genetic disorders.
To suffer from the disease a person must inherit both changed forms of the dominant gene.
An example is sickle cell anaemia

27. SS – sickle cell sufferer
AA – normal
SA – sickle cell trait

28. d. Ante- natal and post-natal screening
What do you know?
What is ante-natal screening?
How is it done
Why is it done?
What is post-natal screening?
How is it done?
What is a pedigree chart and why are they made?