2.16 - 2.18 cystic fibrosis & genetic screening Flashcards
cystic fibrosis
a serious genetic disease caused by a recessive allele which affects the production of mucus by epithelial cells. it results from one of a number of possible mutations
the chloride transport system of the exocrine glands don’t function properly, leading to production of a thick sticky mucus
exocrine glands
glands which produce substances and secrete them to where they are needed through a small tube called a duct
villi
finger-like projections of the lining of the duodenum and small intestine which increase the surface area for the absorption of digested food
duodenum
the first part of the gut after the stomach
pancreatic duct
the duct from the pancreas which carries digestive enzymes made in the pancreas into the duodenum
insulin
a hormone made in the pancreas involved in the regulation of blood sugar levels
genetic screening
when whole populations are tested for a genetic disease
phenylketonuria (PKU)
a recessive genetic disorder where those affected lack the enzyme needed to digest the amino acid phenylalanine; the amino acid builds up in the blood and causes severe brain damage
prenatal screening
screening of an embryo or fetus before birth
amniocentesis
a type of prenatal screening which involves removing a sample of amniotic fluid at around 16 weeks of pregnancy, culturing the fetal cells found and analysing them for genetic diseases by karyotyping
chorionic villus sampling (CVS)
a type of prenatal screening where a small sample of embryonic tissue is taken from the developing placenta and the cells are tested for genetic diseases by karyotyping
preimplantation genetic diagnosis
testing the cells of an embryo produced by IVF (in vitro fertilisation) to check for genetic diseases before it is implanted into the uterus of the mother
genetic counselling
help people to understand and come to terms with the situation of carrying a faulty allele that can cause a genetic disease, assess the statistical risk of producing an affected child, and help couples recognise their options
what are the disadvantages of amniocentesis? (3)
- it can only be carried out relatively late in the pregnancy, making it very difficult for the parents if termination of the pregnancy is necessary
- the results are not available until 2-3 weeks after the test
- it carries a risk of spontaneous abortions after the procedure, regardless of the genetic status of the fetus
what are the disadvantages of chorionic villus sampling? (2)
- there is a risk that the embryo may spontaneously abort after the tissue sample is taken, though the risk of miscarriage at this stage of pregnancy is high anyway
- all paternal x chromosomes are inactivated in fetal placental cells so any problems in the genes on that chromosome cannot be detected by this technique