Screening Flashcards
Between which weeks does a dating scan take place?
8-14 weeks
Between which weeks does an anomaly scan take place?
18-20 weeks
Name the scan that may detect serious physical abnormalities with the fetus?
Anomaly scan
Name 2 types of tests carried out throughout pregnancy to monitor concentrations of marker chemicals.
a) urine tests
b) blood tests
Name two types of diagnostic testing.
a) Chorionic villus sampling
b) amniocentesis
What is an advantage of CVS over amniocentesis?
It can be done earlier in pregnancy
What is the advantage of amniocentesis over CVS?
Lower risk of miscarriage
What name is given to an individual’s chromosomes arranged as homologous pairs?
Karyotype
Give 3 examples of disorders that can be detected by looking at the karyotype.
1) Down’s syndrome
2) Turner’s syndrome
3) Klinefelter’s syndrome
What do we call different forms of a gene?
allele
What do we call the alleles an organism has for a particular characteristic, usually written as letters e.g. Bb or BB
Genotype
What do we call the visible characteristics of an organism which occur as a result of its genes?
Phenotype
What term is used to describe an allele that always expresses itself whether it is partnered by a recessive allele or by another like itself?
Dominant
What term is used to describe the variant of a gene for a particular characteristic which is masked or suppressed in the presence of the dominant variant?
Recessive
What term is used to describe a genotype where the 2 alleles are identical?
Homozygous
What term is used to describe a genotype where the 2 alleles are different?
Heterozygous
What name is given to the first 22 pairs of chromosomes?
autosomes
What name is given to the 23rd pair of chromosomes?
sex chromosomes
What are the sex chromosomes of a female?
XX
What are the sex chromosomes of a male?
XY
Which of the sex chromosomes is shorter?
Y
Why does the predicted ratio of a phenotype not always match the actual ratio?
Fertilisation is random.
Give an example of a diagnostic postnatal test?
phenylketonuria (PKU)
What causes PKU?
substitution mutation
In PKU an enzyme is altered. What is the substrate and product for this enzyme?
Substrate = phenylalanine Product = tyrosine
In PKU, which chemical can build up and cause brain damage in babies?
phenylalanine
How can PKU be treated?
Placed on a restricted diet
