1. Higher Human Biology Unit 2 – Physiology and Health
Section 12 – Antenatal and Postnatal Screening

2. What Can You Remember?
What is meant by continuous and cyclical fertility?
Describe the process of artificial insemination
What is the purpose of super-ovulation?
Describe the process of ICSI
Describe the process of IVF
What is PGD?
Name two barrier methods of contraception
What is female tubal ligation?

3. a – Antenatal Screening
We will be learning…
To state that a variety of techniques can be used to monitor the health of the mother, developing baby and foetus
Describe the technique of antenatal screening as the process that identifies the risk of a disorder so that further tests and diagnosis can be offered.
Explain the use of ultrasound for dating the foetus and to identify abnormalities.
Describe the diagnostic chemical tests that are carried out to monitor the concentrations of marker chemicals
Describe the process of diagnostic testing such as amniocentesis and chronic villus sampling.
State the advantage and disadvantage of amniocentesis and chronic villus sampling techniques.
That a significant number of cells can be sampled and cultured in order to obtain a karyotype in order to diagnose a range of conditions.

4. Antenatal “before birth” Screening
Antenatal screening is carried out to monitor the health of a pregnant woman and her foetus
Antenatal screening identifies the risk of a disorder so that further diagnosis tests can be carried out and a prenatal diagnosis can be given

5. Antenatal “before birth” Screening
This consists of:
Ultrasound for dating
Ultrasound for detecting abnormalities
Diagnostic chemical testing – marker chemicals
Amniocentesis
Chronic villus sampling

6. Hypertension (High Blood Pressure)
Antenatal Care
During pregnancy the mother is closely monitored. This includes checks on the mother’s :
Antenatal Test
Condition
Blood Pressure
Hypertension (High Blood Pressure)
Medical History
Cystic Fibrosis
Height and Weight
Obesity
Blood Tests
Type/Diabetes
Urine Tests
Renal Failure

8. Ultrasound
Ultrasound is used to create images of soft tissue structures, such as the gallbladder, liver, kidneys, pancreas, bladder, and other organs and parts of the body. 
Ultrasound can also measure the flow of blood in the arteries to detect blockages.
Ultrasound imaging uses sound waves to produce pictures of the inside of the body. It is used to help diagnose the causes of pain, swelling and infection in the body's internal organs and to examine a baby in pregnant women and the brain and hips in infants.
Foetus at 12 weeks

9. Ultrasound – for Dating
Dating scans (done at weeks) give information about the stage of gestation and the due date.
Tests for marker chemicals which vary normally during pregnancy are used with dating scans

10. Ultrasound – for Detecting Abnormalities
Anomaly scans (done at weeks) take a close look at the foetus and the uterus. They can detect serious physical problems

11. Screening vs. Diagnostic Tests
Screening Test
A screening test detects signs and symptoms associated with a disorder
A degree of risk can be assessed
Diagnostic test
A diagnostic test is a definite test which establishes, without doubt, whether a person is suffering from a specific condition or disorder

12. Diagnostic Biochemical Testing
Biochemical tests are used to detect the normal physiological changes of pregnancy through blood and urine samples e.g. HCG
Changes can detect complications e.g. in the condition pre-eclampsia (high blood pressure) the concentration of urea in the plasma is significantly higher than normal and concentration of calcium in the urine is significantly lower

13. Markers
At 16 – 18 weeks the pregnant woman is offered a series of biochemical tests that check for different chemical markers.
Medical conditions can also be detected by a range of marker chemicals that indicate a condition but need not necessarily be part of the condition.

14. Markers
For example, the marker Human Chorionic Gonadotrophin normally HCG increases during weeks 6-10 then decreases to a steady low level
However, it remains high if the foetus has Down’s syndrome

15. False Positives and Negatives
Measuring a substance at the wrong time could lead to a false positive or false negative result
For example, HCG results at 10 weeks could give a false positive and would be meaningless since both a normal pregnancy and a Down’s pregnancy would show elevated results at week 10

16. Diagnostic Tests They are carried out:
If routine screening has indicated an increased risk of a condition
for individuals already in high risk categories (eg women over 35)
If there is a family history of a harmful genetic disorder

17. Risks of Diagnostic Testing
2 main types of diagnostic testing are:
Amniocentesis
Chorionic Villus Sampling (CVS)
Both amniocentesis and CVS increase the risk of miscarriage
In deciding to proceed with these tests, the element of risk associated with the tests must be assessed by the parent(s)

18. Amniocentesis
Amniocentesis is carried out at about weeks of pregnancy
A small amount of amniotic fluid is withdrawn and this contains foetal cells
The cells are cultured to produce a karyotype, this usually takes about 2 weeks
A karyotype is a visual display of a person’s complete chromosome complement, arranged in pairs

19. What is a Karyotype?
A Karyotype allows a doctor to see the number and visual appearance of the chromosomes in the cell nuclei of an organism or species.
To make a karyotype, scientists take a picture of the chromosome from one cell, cut them out, and arrange them using size, banding pattern, and centromere position as guides.

20. Normal Karyotypes of Males and Females
To make a karyotype, scientists take a picture of the chromosome from one cell, cut them out, and arrange them using size, banding pattern, and centromere position as guides.

21. Amniocentesis Advantages Disadvantages
The test determines if there are any genetic or chromosomal abnormalities.
It can identify hundreds of genetic disorders such as Down’s Syndrome, Edwards syndrome and Tay-Sachs disease.
It is the only test that can provide results that are accurate.
It can determine if the babies lungs are healthy if the baby is going to be born prematurely.
Disadvantages
Risk of miscarriage – this depends on the skill of the doctor
Risk of uterine infection following the procedure

22. Down’s Syndrome
Trisomy 21 are quite noticeable—a round face and upturned eyes, and a short, stocky build, for example. People with Down syndrome sometimes move awkwardly, usually due to low muscle tone (hypotonia) at birth that can interfere with physical development.

23. Edward’s Syndrome
A karyotype containing an extra copy of chromosome 18 indicates Edward’s Syndrome
The condition is characterised by unusual skull shape and small chin. The sufferer also has heart and kidney malformations
Very few sufferers live beyond their first year and have profound delay in all aspects of development
It occurs in 1 in 3000 live births

24. Turner’s Syndrome only one X chromosome instead of two
A karyotype with an X chromosome missing indicates Turner’s syndrome
Individuals affected in this way are always female and short in stature
Since their ovaries do not develop, they are infertile and fail to develop secondary sexual characteristics at puberty
It occurs with a frequency of 1 in 2500 female live births

25. Klinefelter’s Syndrome
A karyotype with two X chromosomes and a Y indicates Klinefelter’s syndrome
The affected individual is always male and possesses male sex organs
They are infertile because their testes are very small and fail to produce an sperm
Occurs with a frequency of about 1 in 1000 male live births

26. Chorionic Villus Sampling (CVS)
This involves taking a sample of placental cells
The cells are cultured and used for karyotyping
Has an increased risk of miscarriage compared to amniocentesis but it can be carried out earlier - as early as 8 weeks into pregnancy and allows immediate karyotyping

28. Chronic Villus Sampling
Advantages
Possibility of performing the procedure during the first trimester of pregnancy which means a relatively fast result - CVS is usually done between 10 and 13 weeks of pregnancy. Results are usually available 7 days after the procedure.
Highly accurate
Disadvantages
risk of miscarriage comparable to that in case of amniocentesis

29. Rhesus Antibody Testing
Generally mothers show no immune response to their foetus although sensitisation to rhesus antigens can occur.
This can happen when a rhesus negative mother is first pregnant with a rhesus positive foetus and a mixing of blood at birth occurs causing sensitisation of the mother to rhesus antigens

30. Rhesus Antibody Testing
The immune system of the mother then makes anti-rhesus antibodies and memory cells
A second rhesus positive foetus will be attacked through the placenta by the anti-rhesus antibodies from the mother
The foetus can be saved by replacing the rhesus positive blood with rhesus negative via a transfusion
Or the mother can be injected with anti-rhesus antibodies, just after the birth of the first child, this destroys the rhesus antigen

31. b – Genetic Screening and Counselling
We will be learning…
To draw, analyse and interpret patterns of inheritance through genetic screening and counselling
To describe patterns of inheritance in autosomal recessive, autosomal dominant, incomplete dominance and sex-linked recessive single gene disorders

32. Genetic Screening
This is the study of a person's DNA in order to identify genetic differences or susceptibility to particular diseases or abnormalities.

33. Genetic Counselling
the giving of advice to prospective parents concerning the risks of genetic disorders in a future child
Carrier identification e.g. carrying risk of disease
Prenatal diagnosis
Forensic screening e.g. paternity testing

34. What can you remember about genes, inheritance and genetic crosses?

35. Definitions Revision Haploid Diploid Alleles Recessive Dominant
Homozygous
Heterozygous
Genotype
Phenotype
Gene

36. Monohybrid Cross Revision
Use the following genes and symbols
T = tall plants, t = dwarf;
G = grey body flies, g = black;
R = tongue roller, r = non roller;
Draw out a punnett square and work out ratios of phenotypes for the following crosses
Tt x Tt
Rr X rr
Gg x Gg
Gg x gg
Rr x Rr

37. a) Tt x Tt
b) Rr x rr r r T t R Rr Rr T TT Tt r t rr rr Tt tt
1 roller : 1 non roller
3 tall : 1 dwarf
c) Gg x Gg G g G GG Gg g Gg gg
3 grey : 1 black

38. g g G Gg Gg g gg gg 1 grey : 1 black R r R RR Rr r Rr rr
e) Gg x gg g g G Gg Gg g gg gg
1 grey : 1 black
f) Rr x Rr R r R RR Rr r Rr rr
3 rollers : 1 non roller

39. Pedigree Chart

40. Pedigree Charts and Counselling
Pedigree charts (family trees) are used to analyse patterns of inheritance in genetic screening
Once the phenotype for a characteristic is known and a family tree is constructed most of the genotypes can be determined
This information is used by genetic counsellors to advise parents of the possibility of passing on a genetic condition to their child

41. Different Patterns of Inheritance
A genetic counsellor may recognise:
Autosomal recessive
Autosomal dominant
Autosomal incomplete dominance
Sex linked recessive trait
Remember X and Y chromosomes are sex chromosomes. All other chromosomes are called autosomes.

42. Autosomal Recessive Inheritance
Female sufferer of cystic fibrosis
The trait is:
Expressed relatively rarely
May skip generations
Males and females equally affected
All sufferers homozygous recessive
Non-sufferers homozygous dominant or heterozygous
Male non-sufferer of cystic fibrosis

43. Autosomal Recessive Inheritance
X and Y chromosomes are Sex Chromosomes
All others are known as Autosomes
Cystic Fibrosis is an example of autosomal recessive inheritance
Sufferers are homozygous recessive, cc
Non sufferers are homozygous dominant or heterozygous (CC or Cc)
Cystic fibrosis results from a 3 base pair deletion on chromosome 7 – this produces a non functional protein

44. Deletion on chromosome 7
Mucus is found at various sites in the body These sites include the lungs, the pancreas and the alimentary canal The mucus produced by sufferers of cystic fibrosis becomes thicker and stickier than normal The organs become congested and blocked The frequency, in GB, of being a carrier is 1 in 25 Genetic counsellors use this information during genetic screening

45. Autosomal Recessive Inheritance
A = normal a= cystic fibrosis
What is the probability of these parents’ children having cystic fibrosis? 0%

46. Autosomal Recessive Inheritance
A = normal a= cystic fibrosis
What is the probability of these parents’ children having cystic fibrosis?
25%

47. What is the genotype of person 1 in 1st generation
There is an autosomal blood disorder in which a faulty form of haemoglobin is produced.
The allele for normal haemoglobin (H) is dominant to the allele for faulty haemoglobin (h).
What is the genotype of person
1 in 1st generation
4 in 2nd generation hh Hh

48. Autosomal Dominant Inheritance
Female sufferer of Huntingtons
Males and females affected equally
All non sufferers homozygous recessive
Sufferers homozygous dominant of heterozygous
Male non-sufferer of Huntingtons

49. Autosomal Dominant Inheritance - Huntington’s Chorea
Huntington’s Chorea is an example of autosomal dominant inheritance The trait appears in every generation Each sufferer of the trait has an affected parent When a branch of the family does not express the trait, the trait fails to reappear in future generations of that branch Males and females are affected in approximately equal numbers All non sufferers are homozygous recessive, hh All sufferers are HH or Hh

50. Cause and Prognosis
From previous study, in unit 1, we know that Huntington’s disease is caused by an affected gene on chromosome 4
The type of mutation involved results in the codon CAG being repeated more than 35 times
Lack of correct protein leads to:
Premature death
Decreased production of neurotransmitters
Progressive degeneration of the central nervous system

51. Autosomal Dominant Inheritance
B = Huntington’s Disease sufferer
b = normal
What is the probability of these parents’ children having Huntington’s?
50%

52. Incomplete Dominance
So far we have looked at situations where autosomal alleles are either dominant or recessive
In some cases dominant allele does not fully express itself, this is known as incomplete dominance WW RR RW

53. Incomplete Dominance
When writing out an incomplete dominance cross, both alleles have capitals and a different letter. WW RR P F1 RW RW RW RW RW

54. All F1 offspring are pink.
Incomplete Dominance
If red and a white short flowers are crossed, the offspring appear pink.
Parents (P) Red x White
RR WW W R RW
All F1 offspring are pink.

55. Incomplete Dominance x
If pink flowers were crossed with one another, what proportions of colours would you expect in the F2 generation? (Use a punnet square) x

56. Sickle Cell
Haemoglobin S is much less efficient at carrying oxygen than normal haemoglobin.
People who are homozygous for the abnormal allele (SS) suffer from the condition sickle cell anaemia.
People who are homozygous for the normal allele (HH) produce normal haemoglobin and normal red blood cells.

57. Sickle Cell
People who are heterozygous (HS) do not suffer from sickle cell anaemia, but from a milder condition known as the sickle cell trait.
Heterozygotes possess a phenotype 'in- between' the two homozygous phenotypes. In other words the normal allele is incompletely dominant to the sickle cell allele.

58. Autosomal Incomplete Dominance
The fully expressed form of the disorder occurs relatively rarely
Partially expressed form occurs more frequently
Males and females equally affected

59. Autosomal Incomplete Dominance
Non sufferers are homozygous for one incompletely dominant allele
Sufferers of the fully expressed form of the disorder are homozygous for the other incompletely dominant allele
Sufferers of the partly expressed form are heterozygous for the two alleles

60. Sex linkage The X chromosome is larger than the Y
As a result the X chromosome carries more genes
Genes which are carried on the same sex chromosome are said to be sex-linked.
Use X and Y to represent the sex chromosomes, and superscript letters to represent the alleles eg. XR Xr

61. Sex Linked Recessive
If being colour blind is recessive, cross a male colour blind with a female with colour vision who is a non carrier
XbY XBXB Xb Y XB XB
Female with normal colour vision
Male with normal colour vision
Sons get the Y from their dad,therefore
they must inherit the disease from their
mother
Daughters have to get the recessive gene
from both parents to inherit the condition
XBXb
(1)
XBY
(2)
(3)
(4) Y Xb XB XB

62. Sex Linked Recessive
Sufferers of the trait are homozygous recessive, normally male XhY
Non sufferers are homozygous dominant XHY XHXH or are heterozygous female carriers XHXh – they don’t suffer form the condition but carry a copy of the. gene which they can pass on to their offspring
Carrier mother
Carrier daughter

63. Sex Linked Recessive Many more males are affected than females
None of the sons of an affected male show the trait
Some of the grandsons of an affected male do show the trait
Carrier daughter
Carrier daughter

64. Haemophilia
A protein called Factor VIII is required for the blood clotting Haemophilia (blood does not clot or takes a very long time to clot) is caused by a recessive gene which is carried on the X chromosome H represents normal blood clotting and h represents haemophilia Colour blindness and haemophilia are rare in females since two recessive alleles must be inherited

65. Haemophilia Genotype Phenotype XH XH Normal female XH Xh
‘Carrier’ female
Xh Xh
Haemophiliac female
XH Y
Normal male
Xh Y
Haemophiliac male

66. c – Postnatal Screening
We will be learning…
To describe the processes involved in postnatal screening.
Describe the diagnostic test for phenylketonuria (PKU)
Explain how PKU is treated

67. Post Natal Screening
New-born screening is a public health program of screening in infants shortly after birth for a list of conditions that are treatable, but not clinically evident in the new-born period.

68. Diagnostic Test for PKU
Phenylketonuria (PKU) is a rare genetic disorder that is present from birth. In PKU, the body is unable to break down an amino acid called Phenylalanine which then builds up in the blood and in the brain and can cause problems when untreated.
The treatment for PKU is effective.  It involves a protein restricted diet for life and taking regular dietary supplements which contain amino acids, vitamins and minerals.  The aim is to keep the blood Phenylalanine level within a specific target range.
A PKU test is done a day or two after your baby's birth. The test is done after your baby is 24 hours old and after your baby has ingested some protein in the diet to ensure accurate results. A nurse or lab technician collects a few drops of blood from your baby's heel or the bend in your baby's arm.

69. Phenylketonuria (PKU)
The amino acid phenylalanine is found in the diet.
enzyme C
melanin
(Skin pigment)
Intermediate metabolites
enzyme B
enzyme A
phenylalanine
tyrosine
(an amino acid)
In a PKU sufferer the gene that codes for enzyme 1 is defective – what will this result in?

70. Phenylketonuria (PKU)
enzyme B
tyrosine
(an amino acid)
melanin
(Skin pigment)
enzyme C
Intermediate metabolites
enzyme A
phenylalanine
Phenylalanine builds up in the blood .

71. Phenylketonuria (PKU)
PKU is an autosomal recessive inherited metabolic disorder.
Phenylalanine builds up in the blood and causes mental development to be restricted
It is fairly common in the UK – about 1 in 10,000 live births.
PKU is routinely tested for in newly born babies using a Heel prick test.
PKU can be treated by following a
low phenylalanine diet

73. Phenylketonuria (PKU)
Sufferers usually have a lighter skin pigment than normal, but will not be albino as some tyrosine will be present in their diet and this can re-instate the end of the pathway so some melanin is still made.
enzyme C
melanin
(Skin pigment )
Intermediate metabolites
enzyme B
tyrosine
(an amino acid)

74. Albinism
Albinos cannot make enzyme C and are therefore unable to make melanin.
This protein is the dark pigment in skin and other organs, including the retina

75. Now I can…..
a – Antenatal Screening
State that a variety of techniques can be used to monitor the health of the mother, developing baby and foetus
Describe the technique of antenatal screening as the process that identifies the risk of a disorder so that further tests and diagnosis can be offered.
Explain the use of ultrasound for dating the foetus and to identify abnormalities.
Describe the diagnostic chemical tests that are carried out to monitor the concentrations of marker chemicals
Describe the process of diagnostic testing such as amniocentesis and chronic villus sampling.
State the advantage and disadvantage of amniocentesis and chronic villus sampling techniques.
State that a significant number of cells can be sampled and cultured in order to obtain a karyotype in order to diagnose a range of conditions.

76. b – Genetic Screening and Counselling
Now I can…..
b – Genetic Screening and Counselling
Draw, analyse and interpret patterns of inheritance through genetic screening and counselling
Describe patterns of inheritance in autosomal recessive, autosomal dominant, incomplete dominance and sex-linked recessive single gene disorders

77. c – Postnatal Screening
Now I can…..
c – Postnatal Screening
To describe the processes involved in postnatal screening.
Describe the diagnostic test for phenylketonuria (PKU)
Explain how PKU is treated

78. Chronic Villus Sampling (CVS)
Word
Meaning
Allele
form of a gene coding for a version of a characteristic
Amniocentesis
prenatal test to assess health of foetus using cells from amniotic fluid
Anomaly Scan
antenatal ultrasound scan that checks for physical abnormalities
Antenatal Screening
use of tests to identify risk of a disorder before birth
Autosomal Dominant
allele on chromosomes 1-22; always expressed in phenotype
Autosomal Recessive
allele on chromosomes 1-22; expressed in phenotype if the genotype is homozygous for the recessive allele
Chronic Villus Sampling (CVS)
prenatal test to assess health of the foetus using cells from the placenta
Embryo
stage of development up to about 8 weeks that leads to the formation of a foetus
Feotus
stage of a baby after 8 weeks of development
Heterozygous
having two different alleles of the same gene
Homozygous
having two identical alleles of the same gene

79. Rhesus Antibody Testing
Word
Meaning
Incomplete Dominance
when an allele is not completely masked by a dominant allele, thus affecting an individual's phenotype
Karyotype
display of matched chromosomes produced for medical purposes
Pedigree Chart
diagram showing the occurrence of phenotypes of a particular gene in a family tree
Phenylketonuria
metabolic disorder that is tested for by postnatal screening
Postnatal Screening
diagnostic testing of newborn babies
Prenatal Diagnosis
identification of the risk of sisorders in unborn babies
Rhesus Antibody Testing
testing to show if a person carries rhesus antibodies in their blood
Sex-linked Recessive
recessive allele carried on the X chromosome
Ultrasound Scanning
diagnostic procedure used for various prenatal checks, such as establishing the stage of pregnancy and the date that the baby is due

80. Give an account of the tests which can be carried out once a woman has been confirmed as pregnant, under the headings:
screening tests; (6 marks)
diagnostic tests. (4 marks)

81. Screening tests (maximum of 6 marks):
Screening indicates possibility of a condition.
Ultrasound dating scan at 8-14 weeks indicates age of foetus / likely due date.
Ultrasound anomaly scan at weeks indicates possible unusual development, associated with e.g. Down's syndrome.
Biochemical tests on blood samples.
Levels of marker chemicals inappropriate to stage of pregnancy, e.g. α- foeto protein indicate possible presence of Down's syndrome.
Diagnostic tests (maximum of 4 marks):
Diagnostic tests confirm the presence of condition.
Amniocentesis removes cells from the amniotic fluid and are carried out at about 18 weeks
Chorionic villus sampling removes cells from the placenta and are carried out at weeks.
Karyotyping - examination of foetal chromosomes.

82. HHB Specimen Question 8 B

83. HHB Specimen Question 9

84. HHB Specimen Question 13 A

86. HHB Question 12 D