Physiology and Health Unit 2 KA 4

Question 1

What is the purpose of Antenatal (prenatal) screening?

Answer 1

The purpose of Antenatal (prenatal) screening is to identify the risk of a disorder so that further tests and a prenatal diagnosis can be offered

Question 2

What are examples of Antenatal (prenatal) screening? (7)

Answer 2

1) Ultrasound imaging (Dating and Anomaly scan)
2) Biochemical tests
3) Diagnostic tests
4) Use of Karyotype
5) Amniocentesis
6) Chorionic villus sampling
7) Rhesus antibody testing

Question 3

How does an Ultrasound scanner work?

Answer 3

An Ultrasound scanner is held against the womans abdomen, it picks up high frequency sounds that bounce off the foetus and these are converted to an ultrasound image

Question 4

When is a Dating scan carried out?

Answer 4

A Dating scan is carried out between 8-14 weeks

Question 5

What is the purpose of a Dating scan?

Answer 5

A Dating scan determines the stage of the pregnancy and is used to calculate the due date

(Used alongside a test for chemical markers)

Question 6

When is an Anomaly scan carried out?

Answer 6

An Anomaly scan is carried out between 18-20 weeks

Question 7

What is the purpose of an Anomaly scan?

Answer 7

An Anomaly scan detects the presence of any serious physical abnormalities in the foetus

Question 8

What do Biochemical tests monitor?

Answer 8

Biochemical tests monitor the physiological changes that occur during pregnancy

Question 9

Why are routine blood and urine tests carried out throughout pregnancy?

Answer 9

Routine blood and urine tests are carried out throughout pregnancy to monitor the concentrations of marker chemicals

Question 10

What can happen if screening is conducted at the wrong time?

Answer 10

If screening is conducted at the wrong time a false positive may occur

Question 11

Why is a Screening test carried out?

Answer 11

A screening test is carried out to detect signs/symptoms associated with a certain condition or disorder.
If signs are found the probability that the foetus will suffer with the condition can be assessed as a degree of risk

Question 12

A Diagnostic test is a definitive test, what does this mean?

Answer 12

A Diagnostic test is a definitive test meaning it can produce results that can be used to establish without a doubt whether or not the foetus is suffering with a condition or disorder

Question 13

When might a Diagnostic test be offered? (3)

Answer 13

1) Screening tests have shown a potential problem
2) There’s a family history of a genetic disorder
3) The women belongs to a high risk group (over the age of 35)

(Diagnostic testing comes with a risk)

Question 14

When is Amniocentesis carried out?

Answer 14

Amniocentesis is carried out between 14-16 weeks

Question 15

What is involved in Amniocentesis?
(Type of Diagnostic testing)

Answer 15

Amniocentesis involves withdrawing amniotic fluid containing foetal cells
The cells are examined and a karyotype is created so chromosome abnormalities can be detected

(There is a risk of miscarriage)

Question 16

When is Chorionic Villus Sampling (CVS) carried out?

Answer 16

CVS is carried out at 8 weeks which is an advantage over Amniocentesis which has to be carried out later (14-16)

Question 17

What is involved in Chorionic Villus Sampling (CVS)?
(Type of Diagnostic testing)

Answer 17

CVS involves taking a tiny sample of placental cells using a fine tube inserted into the mothers reproductive tract
The cells are used for karyotyping

(Higher risk of of miscariage)

Question 18

What can Pedigree charts be used for?

Answer 18

Pedigree charts can be used to analyse patterns of inheritance in genetic screening and counselling

Question 19

What are the two Sex chromosomes?
What are all other chromosomes called?

Answer 19

The two Sex chromosomes are X and Y chromosomes
All other chromosomes are called Autosomes

Question 20

What patterns can be spotted in Autosomal Recessive Inheritance? (6)

Answer 20

1) Trait is expressed relatively rarely
2) Trait may skip generations
3) Trait is expressed in some offspring of cousin marriages
4) Males and females affected equally
5) Genotype of sufferers are homozygous recessive (ff)
6) Genotype of non-sufferers are homozygous dominant or heterozygous (FF/Ff)
E.G. Cystic Fibrosis

Question 21

What patterns can be spotted in Autosomal Dominant Inheritance? (6)

Answer 21

1) Trait is expressed in every generation
2) Each sufferer of the trait has an affected parent
3) When a branch of the tree fails to express the trait, the trait will not reappear later in that branch
4) Males and females affected equally
5) Sufferers are homozygous dominant or heterozygous (HH/Hh)
6) Genotype of non-sufferers are homozygous recessive (hh)
E.G. Huntingtons disease

Question 22

What patterns can be spotted in Autosomal Incomplete Inheritance? (7)

Answer 22

1) Fully expressed form occurs relatively rarely
2) Partly expressed form occurs much more frequently
3) Each sufferer of the fully expressed forma has two parents who suffer from the partly expressed form
4) Males and females affected equally
5) All sufferers of the fully expressed form are homozygous for the other incompletely dominant allele (SS)
6) All sufferers of the partly expressed form are heterozygous for the two alleles (HS)
7) All non-sufferers are homozygous for one incompletely dominant allele (HH)
E.G. Sickle-cell disease

Question 23

What patterns can be spotted in Sex-linked Recessive Inheritance? (5)

Answer 23

1) Many more males affected than females (if any)
2) None of the sons of an affected male will show the trait
3) Some grandsons of the affected male show the trait
4) All sufferers of the trait are homozygous recessive (hh)
5) Non-sufferers are homozygous dominant (HH) or heterozygous female carriers (Hh)
E.G. Haemophilia

Question 24

When is diagnostic testing for metabolic disorder carried out?

Answer 24

Diagnostic testing for metabolic disorders is carried out when the baby is a few days old

Question 25

In the UK all babies are screened for PKU (Phenylketonuria), what is this?

Answer 25

PKU sufferers have excess phenylalanine in their bloodstream, some of this is converted into phenylpyruvic acid
Excess phenylalanine disrupts the development of organs and the brain
Sufferers are put on a restricted diet to prevent mental deficiency