Chapter 5 Flashcards
alleles
copies of a gene
homozygous
two genes are alike
recessive
if a trait is only expressed in a homozygote
heterozygous
two genes are different
dominant
if trait is expressed
carrier
if you are heterozygous for a recessive trait and do not show it
X or Y chromosome
sex-linked
autosomal dominant
need only one defective gene
autosomal recessive
need 2 defective genes
single gene disorders
caused by a single defect or mutated gene: can be on the X chromosome or autosome
penetrance
likelihood that a person who has the autosomal dominant trait, is to express s/s of that gene
variable expressivity
range of signs and symptoms that can occur in different people with the same genetic conditon
monosomy
only one member of the chromosomal pair is present (Turner’s syndrome XO)
polysomy
more than 2 chromosomes to a set
trisomy 21
down syndrome
trisomy 18
Edwards syndrome
extra x chromosome in male XXY
klinefelter’s syndrome
What are the different types of genetic testing a pregnant women can undergo
- amniocentesis
- chorionic vili sampling
- cell free fatal DNA testing
amniocentiesis
when the baby is in utero it is surrounded by amniotic fluid and sheds skin cells. under ultrasound a clinician will insert a needle through the abdominal cavity into the amniotic sac and collect the fluid. they will put this fluid in a petri dish and let it replicate, then stop and look at the chromosomes
- can be done at 16 weeks
- can cause an increased risk of miscarriage
chorionic vili sampling
trans-abdominally or trans-vaginally, depending on how the placenta I situated and you collect these chorionic vili and put them in a petri dish allowing them to grow, then do a carrier type test.
- can be done at 10 weeks
- increased risk for miscarriage
cell free fetal DNA testign
some fetal cells enter the maternal circulation. do a blood test on the mom and seperate the mom cells from the fetal cells, and take those cells, grow them and do a carrier type test
- non invasive
- can be done at 10 wks
