Genetic screening Flashcards
when is identifying carriers carried out
from birth onwards to adult (normally adults)
how is identifying carriers carried out
white blood cells collected from blood sample or cheek cells from mouth swab
DNA is extracted from cell nucleus and is analysed to detect defective gene nucleus
what are the disadvantages of identifying carriers
emotional stress of finding out your a carrier or due to other abnormalities found
false positives or false negatives result (tests aren’t 100% accurate)
screening does not test for all possible mutations that can cause cystic fibrosis
when is amniocentesis carried out
when foetus is in uterus between15-17 weeks
how is amniocentesis carried out
foetal cells are collected from the amniotic fluid surrounding foetus using a needle into the abdomen
DNA is extracted and analysed to detected defective gene mutation
what are the disadvantages of amniocentesis
risk of miscarriage (0.5%-1%) - loss of healthy foetus
not 100% accurate
false positive could result in abortion of healthy foetus
emotional and physical stress of choosing an abortion
when is chronic villus sampling (CVS) carried out
when foetus is in uterus between 8-12 weeks
how is chronic villus sampling carried out
foetal cells are collected from placenta using a needle into abdomen or cervix
DNA extracted from placenta is analysed to detect defective gene
what are the disadvantages of chronic villus sampling
risk of miscarriage (1-2%) - loss of healthy foetus
false positive could result in abortion of healthy foetus
emotional and physical stress of choosing abortion
when is the non-invasive prenatal diagnosis (NIPD) carried out
when foetus is in uterus between 7-9 weeks
how is non-invasive prenatal diagnosis carried out
mothers blood plasma analysed for the presence of cell free foetal DNA fragments
DNA is extracted and analysed to detect defective gene mutation
what are the disadvantages of non-invasive parental diagnosis
false positive could result in abortion of a healthy foetus
emotional and physical stress of choosing an abortion
when is the pre-implantation genetic diagnosis carried out
at the 8 cell embryo stage
during IVF
how is pre-implantation genetic diagnosis carried out
one cell is taken from the embryo
DNA is extracted and analysed to detect defective gene mutation
what are the disadvantages/implications of pre-implantation genetic diagnosis
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 low success rate
