genetic screening- lqc 10

Question 1

when is amniocentesis carried out

Answer 1

When foetus is in uterus - between 15 - 17 weeks

Question 2

how is amniocentesis carried out

Answer 2

Foetal cells are collected from the amniotic fluid surrounding the foetus using a needle into abdomen DNA is extracted and analysed to detect defective gene mutation

Question 3

disadvantages of amniocentesis

Answer 3

• Risk of miscarriage (0.5% -1%) - loss of healthy foetus
• False positive- could result in abortion of a healthy foetus
• Emotional and physical stress of choosing an abortion

Question 4

when is chorionic villus sampling carried out

Answer 4

When foetus is in uterus - between 8 - 12 weeks

Question 5

how is chorionic villus sampling carried out

Answer 5

Foetal cells are collected from the placenta using a needle into abdomen or vagina

Question 6

disadvantages of chorionic villus sampling

Answer 6

• Risk of miscarriage (1-2%) - loss of healthy foetus
• False positive- could result in abortion of a healthy foetus
• Emotional and physical stress of choosing an abortion

Question 7

when is NIPD carried out

Answer 7

When foetus is in
uterus - between 7 - 9 weeks

Question 8

how is NIPD carried out

Answer 8

Analyses cell free fetal DNA (cffDNA) from the mothers blood plasma, DNA is extracted and analysed to detect defective gene mutation

Question 9

disadvantages of NIPD

Answer 9

• False positive could result in abortion of a
  healthy foetus
• Emotional and physical stress of choosing an abortion

Question 10

NIPD stands for

Answer 10

Non-invasive prenatal diagnosis

Question 11

when is PGD carried out

Answer 11

At the 8 cell embryo stage– during IVF

Question 12

how is PGD carried out

Answer 12

One cell is taken
from the embryo, DNA is extracted and analysed to detect defective gene mutation

Question 13

disadvantages of PGD

Answer 13

• False negative result means parents may still have a baby with CF and are unprepared
• Could be used to discover other characteristics e.g. eye colour, gender
• IVF is expensive, stressful and has a low success rate

Question 14

PGD stands for

Answer 14

Pre-implantation genetic diagnosis

Question 15

when are identifying carriers carried out

Answer 15

From birth onwards to adult (normally adults)

Question 16

how is identifying carriers carried out

Answer 16

White blood cells collected from blood sample or cheek cells from a mouth swab, DNA is extracted from cell nucleus and is analysed to detect defective gene mutation

Question 17

disadvantages of identifying carriers

Answer 17

• Emotional stress of finding out you are a carrier or due to other genetic abnormalities found
• False positive or
  false negative result (tests are not 100% accurate)
• Screening does not test for
  all possible mutations that can cause cystic fibrosis

Question 18

What are the social and ethical issues related to genetic screening?

Answer 18

• foetus is living, abortion is wrong / murder
• who has right to decide if tests should be performed, implications of medical costs / disagreements over next step
• that or some other abnormality may be found, comment on possible problems with future employment / insurance;
• who has the right to make the decision for the foetus / foetus has decision rights (if the test is positive), foetus has a right to live
• issues relating to confidentiality of {parents / child}, idea that {some other abnormality may be found / paternal DNA does not match / other family members have right to know results}
• not fully understanding possible risks of prenatal testing, possibility of miscarriage / harm to child