Antenatal and Postnatal testing

Question 1

What’s is antenatal screening

Answer 1

Antenatal screening assesses the health of the mother and tests for diseases/. conditions in an embryo/foetus before birth.

Question 2

what disorders can be identified by antenatal screening?

Answer 2

• Down Syndrome
• Spina Bífida
• Cystic Fibrosis
• Muscular dystrophy

Question 3

when is the dating scan given and what does it do?

Answer 3

It’s given at 8-14 weeks and is used to determine the stage of pregnancy and the due date of the baby

Question 4

when is the anomaly scan given and what does it do?

Answer 4

It’s given at 18-20 and is used to detect any physical abnormalities in the developing foetus.

Question 5

why is the dating scan so important for biochemical tests?

Answer 5

If the stage of pregnancy was wrongly calculated the results would appear skewed and could indicate a problem with the foetus.

Question 6

what condition could be suggested if the blood concentrations during pregnancy are too high?

Answer 6

a neural tube defect (Spina Bifida)

Question 7

what condition could be suggested if the blood concentrations during pregnancy are too low?

Answer 7

chromosomal abnormality (Down syndrome)

Question 8

what would be offered if a positive result came up in biochemical testing?

Answer 8

a diagnostic test

Question 9

what are the two diagnostic tests?

Answer 9

• Amniocentesis
• Chronic Villus Sampling (CVS)

Question 10

What are the advantages of of Amniocentesis?

Answer 10

• lower risk of miscarriage
• detects chromosomal abnormalities and neutral tube defects

Question 11

What are the disadvantages of Amniocentesis?

Answer 11

• carried out later
• cells collected and cultivates takes long (several weeks for karyotype)

Question 12

What are the advantages of Chronic Villus Sampling?

Answer 12

• carried out earlier (placental tissue collected and cultured into an instant karyotyoe)

Question 13

What’s are the disadvantages of Chronic Villus Sampling?

Answer 13

• Higher risk of miscarriage
• Detect only chromosomal abnormalities

Question 14

what Chromosome is affected by Tuner Syndrome and what is the impact

Answer 14

• only one x chromosome
  impact: lower fertility rate

Question 15

what chromosome is affected by klinefelter syndrome and what is the impact?

Answer 15

• 2 x chromosomes and a y chromosome
  impact: - lower fertility
• slightly feminised physique

Question 16

What chromosome is affected by Edward’s syndrome and what is it’s impact?

Answer 16

• The 10th chromosome is affected
  impact: - organ systems affected
• babies tend not to live for longer than a few months

Question 17

What chromosome is affected by Down Syndrome and what is the impact?

Answer 17

• the 21st set of chromosomes are effected
  impact: - lower lifespan
• holes in the heart are more common
• learning difficulties

Question 18

What are the 4 types of single gene disorder? and examples of each one

Answer 18

• Autosomal recessive ( Cystic Fibrosis and Albinism)
• Autosomal dominant (Huntington’s and Chorea)
• Autosomal incomplete dominance ( Sickle Cell Anemia)
• Sex-linked recessive ( Haemophilia)

Question 19

What are the patterns of inheritance for Autosomal Recessive traits?

Answer 19

• the trait is expressed rarely
• tends to skip generations
• all sufferers have a double recessive genotype
• non-suffers are homozygous dominant or heterozygous

Question 20

What are the patterns of inheritance for Autosomal dominant?

Answer 20

• appears in every generation
• each sufferer has an effected parent
• when a branch of the family doesn’t express the trait it wont appear in that future line
• affects males and females equally
• all non-sufferers are homozygous recessive
• all sufferers are homozygous are homozygous dominant or heterozygous

Question 21

What are the patterns of inheritance for Autosomal Incomplete Dominance?

Answer 21

• Fully expressed form occurs rarely
• partially expressed form occurs more frequently
• each sufferer of the fully expressed form has two parents who suffer the partly expressed
• males and females are effected equally
• all non-sufferers are homozygous dominant for the incomplete allele
• there are no recessive alleles

Question 22

What are the the patterns of inheritance for sex-linked recessive?

Answer 22

• more males effected than females
• none of the sons of an effected male have the trait unless the mum is effected
• some grandsons will show the trait
• all non sufferers are homozygous recessive
• non-suffers are homozygous dominant or heterozygous carriers in females.

Question 23

why are more males affected by sex-linked recessive mutations?

Answer 23

because the trait will always be expressed on the x chromosome

Question 24

what is postnatal screening?

Answer 24

Diagnostic tests that occur after the birth to detect the presence of conditions such as phenylketonuria using a blood test.

Question 25

what is the treatment for PKU?

Answer 25

Infants with PKU are placed on a low protein diet.

Question 26

What type is genetic disorder is PKU?

Answer 26

autosomal recessive