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Z. 0Higher Human Biology > 2.4 - Antenatal & Postnatal Screening > Flashcards

2.4 - Antenatal & Postnatal Screening Flashcards

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1
Q

Why is antenatal screening used?

A

Antenatal screening is carried out to monitor the health of a pregnant woman and the developing foetus.

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2
Q

What does antenatal screening identify?

A

Antenatal screening identifies the risk of a disorder so that further tests can be carried out and a prenatal diagnosis can be offered.

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3
Q

What are the three methods of antenatal screening

That we are focusing on

A

Ultrasound imaging

Biochemical tests

Diagnostic tests

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4
Q

What do ultrasound scans do and how did they do it?

A

Ultrasound scans use soundwaves to build a picture of the developing fetus in the uterus.

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5
Q

What are the two ultrasound scans that pregnant women are given?

A
  • dating scan

- anomaly scan

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6
Q

When does a dating scan take place

A

A dating scan takes place between 8 and 14 weeks?

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7
Q

What do dating scans determine?

A

Dating scans determine the stage of pregnancy and the due date.

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8
Q

What are dating scans used with?

A

Dating scans are used with tests for marker chemicals which vary normally during pregnancy.

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9
Q

What can anomaly scans detect?

A

Anomaly scans may detect serious physical abnormalities in the foetus.

It looks in detail at the bones, heart, brain, spinal-cord, face, kidneys and abdomen.

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10
Q

When does an anomaly scan take place?

A

An anomaly scan takes place between 18 and 20 weeks

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11
Q

What are biochemical tests used for

A

Biochemical tests are used to detect the normal physiological changes of pregnancy. 

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12
Q

What do biochemical tests include?

A

These tests include:

  • blood pressure
  • blood type
  • general health checks including routine blood and urine tests
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13
Q

Biochemical tests - what can lead to a false positive result?

A

Measuring a chemical at the wrong time could lead to a false positive result.

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14
Q

Diagnostic testing - What can an atypical chemical concentration lead to?

A

An atypical chemical concentration can lead to diagnostic testing to determine if the fetus has a medical condition.

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15
Q

Diagnostic testing - How can medical conditions be detected?

A

Medical conditions can be detected by a range of marker chemicals that indicate a condition, but may not necessarily be part of the condition.

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16
Q

Diagnostic testing- result of routine screening

A

As a result of routine screening or for individuals in high risk categories, further tests may be offered

In deciding to proceed with these tests, the element of risk will be assessed as will the decision the individuals concerned are likely to make if a test is positive

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17
Q

Diagnostic testing- further tests possibilities

A

Amniocentesis

Chronic villus sampling (CVS)

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18
Q

What is a Karyotype produced from

A

Cells from samples from amniocentesis or CVS can be cultured to obtain sufficient cells to produce a karyotype

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19
Q

What is a karyotype

A

A karyotype is an image of an individuals chromosomes arranged in homologous pairs

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20
Q

How can karyotypes be used

A

Karyotypes can be used to diagnose a range of conditions

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21
Q

What is the karyotype used to identify

A

The karyotype is used to identify anomalies in terms of the numbers or structures of chromosomes

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22
Q

What does amniocentesis involve

A

Amniocentesis involves in the withdrawal of amniotic fluid containing fetal cells

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23
Q

When is amniocentesis carried out

A

Amniocentesis as carried out around 14 to 16 weeks of pregnancy

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24
Q

Amniocentesis - cells and how long it takes

A

Cells are cultured and karyotype examined. The process takes two weeks

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25
Q

What does chorionic villus sampling involve

A

CVS involves a sample of placental cells being removed. It is carried out eight weeks into pregnancy

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26
Q

CVS disadvantage

A

Higher risk of miscarriage (1-2%)

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27
Q

CVS advantage

A

Earlier termination possible

Karyotyping can be performed in the feral cells immediately

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28
Q

What are pedigree chart is used for

A

Pedigree chart are used to analyse patterns of inheritance in genetic screening and counselling

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29
Q

Genetic screening and counselling – what can happen once the phenotype for a characteristic is known

A

Once the phenotype for a characteristic is nine 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

30
Q

Why are routine blood and urine tests carried out

A

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

31
Q

What is a carrier

A

A carrier is a person who carries one copy of the faulty gene but doesn’t show the genetic condition.

However they can pass the gene to their offspring.

32
Q

Describe fertilisation

A

Fertilisation is a random process.

33
Q

What are autosomes

A

The autosomes are all chromosomes except from the sex chromosomes

34
Q

What do the sex chromosomes determine

A

The sex chromosomes are the two chromosomes that determine the sex of an individual

35
Q

What are the patterns of inheritance

A

Autosomal recessive

Autosomal dominant

Incomplete dominance

Sex linked recessive

36
Q

Autosomal recessive inheritance - How often are the expressed

A

Autosomal recessive traits are expressed rarely and may skip generations

37
Q

Autosomal recessive inheritance - Are males and females affected equally

A

Males and females are affected equally

38
Q

Autosomal recessive inheritance - What are the suffers described as

A

Homozygous recessive

39
Q

Autosomal recessive inheritance - Who are not affected

A

Homozygous dominant individuals are not affected

40
Q

Autosomal recessive inheritance - Who are carriers

A

Heterozygous individuals are carriers of the condition. They do not show the condition themselves but they can pass it on to their offspring

41
Q

Autosomal recessive inheritance - example

A

Cystic fibrosis

42
Q

Autosomal dominant inheritance - expressed

A

Appears in every generation

43
Q

Autosomal dominant inheritance - How are males and females affected

A

Males and females are affected equally

44
Q

Autosomal dominant inheritance - How can sufferers be described

A

Sufferers can be either homozygous dominant or heterozygous

45
Q

Autosomal dominant inheritance - What are all non-suffers described as

A

Homozygous recessive

46
Q

Autosomal dominant inheritance - What happens when a branch of the family does not express the treat

A

When a branch of the family does not express the trait it fails to reappear in future generations of the branch

47
Q

Autosomal dominant inheritance - example

A

Huntington’s disease

48
Q

Autosomal incomplete dominance - Describe it

A

Sometimes the dominant allele may not fully express itself which is known as incomplete dominance

49
Q

Autosomal incomplete dominance - Are males and females equally affected

A

Males and females equally affected

50
Q

Autosomal incomplete dominance - How often does the fully express form of the disorder occur

A

The fully expressed form of the disorder occurs relatively rarely

51
Q

Autosomal incomplete dominance - How often is the partially expressed form of the disorder expressed

A

Partially expressed form of the disorder occurs more frequently than the fully expressed form

52
Q

Autosomal incomplete dominance - What are nonsufferers described as

A

Nonsufferers are homozygous for one incompletely dominant allele

53
Q

Autosomal incomplete dominance - How are sufferers of the fully expressed form of the disorder describe as

A

Sufferers of the fully expressed form of the disorder are homozygous for the other incompletely dominant allele

54
Q

Autosomal incomplete dominance - How are sufferers of the partly expressed form described as

A

Sufferers of the partly expressed form are heterozygous for the two alleles

55
Q

Autosomal incomplete dominance - example

A

Sickle cell anaemia

56
Q

Other than determining sex what are the functions of the sex chromosomes

A

Although the sex chromosomes are mainly responsible for determining sex they also carry some genes that code for a number of body functions.

These genes are described as sex linked

57
Q

Explain the differences in size between the X and Y chromosome

A

There is a difference in size between the X and Y chromosome.

The Y chromosome is shorter and therefore some genes appears
only on the X chromosome.

58
Q

Sex linked recessive - Compare how males and females are affected

A

Many more males are affected than females.

This is because the X chromosome will show in the phenotype as there is no dominant allele present to override it.

A female will have another allele on her ex chromosome which, if dominant, would mask the effect of the recessive allele

59
Q

Sex linked recessive - How do male offspring inherit the condition

A

Male offspring inherit the condition from their mother.

60
Q

Sex linked recessive - Why can’t fathers pass the condition to their son

A

Fathers cannot pass the condition to their son therefore none of the sons of an affected male show the trait

61
Q

Sex linked recessive - How are sufferers of the trait described

A

Sufferers of the trait are homozygous recessive

62
Q

Sex linked recessive - How are non-sufferers of the trait described

A

Nonsufferers of the trait are homozygous dominant

63
Q

Sex linked recessive - Who are carriers of the trait

A

Heterozygous females are carriers

64
Q

Sex linked recessive condition - example

A

Haemophilia

65
Q

What is Pre-implantation genetic diagnosis (PGD)

A

Pre-implantation genetic diagnosis is a technique that enables people with a specific inherited condition in their family to avoid passing it on to their offspring.

It involves checking the genes of embryos created through IVF for this genetic condition

66
Q

IVF process

A

During IVF:

  • The embryo is grown in the laboratory for a few days until it consists of around eight cells
  • And embryologist Removes one or two of the cells from the embryo and tests them to see if the embryo from which they were removed contains the gene that causes the genetic condition in the family
  • Embryos unaffected by the condition or transferred to the womb to allow them to develop.
67
Q

When does postnatal screening take place

A

Postnatal screening takes place after birth

68
Q

What does the purpose of postnatal screening

A

Postnatal screening aims to detect certain conditions and abnormalities

69
Q

How can post natal screening be used

A

Postnatal screening can be used to detect metabolic disorders

Such as phenylketonuria (PKU)

70
Q

Phenylketonuria (PKU) - What does a substitution mutation mean

A

In PKU, A substitution mutation means that the enzyme which converts phenylalanine to tyrosine is non-functional.

71
Q

What happens if PKU is not detected and treated soon after birth

A

If PKU is not detected and treated soon after birth the child’s mental development is affected.

72
Q

What happens to individuals born with high levels of phenylalanine

A

Individuals born with high levels of phenylalanine are placed on a restricted diet

Z. 0Higher Human Biology (19 decks)

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