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?

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

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

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)

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.

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

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

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

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

Karyotype Arrangement of analysed chromosomes into homologous pairs.

Down’s syndrome karyotype

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

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

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

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

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

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

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

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

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

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?