2.4 Flashcards
Ante-natal screening is
Antenatal screening monitors health of mother and foetus and identifies risk of a disorder and may allow for a prenatal diagnosis to be given .
Types of antenatal screening
Ultra sound scanning
Blood/Urine tests
Types of ultra sound scanning
Dating scan
Anomaly scan
When are dating scans used and what are they for
8-14 weeks into pregnancy
Dates pregnancy and due date, used with blood and urine tests
When are anomaly scans used and what for
18-20 weeks into pregnancy
Checks for physical abnormalities
Explain blood and urine tests
There are some chemicals that can show up in a mothers blood and urine that may indicate a problem with pregnancy/foetus. These are marker chemicals.
What are marker chemicals
Chemicals that show up in mothers blood/urine indicating problem with foetus or pregnancy
What happens if marker chemical found in urine/blood
Diagnostic testing carried out
What is diagnostic testing used for
Diagnostic testing is used to check for genetic abnormalities such as Down’s syndrome and edwards syndrome.
Risk of diagnostic testing
Miscarriage
Types of diagnostic testing
Amniocentesis
CVS
Diagnostic testing criteria is
Marker chemicals and ultra sounding screening indicate problem
High risk individuals (over 35, obese)
Family history / parents carriers of genetic condition
Explain how amniocentesis carried out
Cells from foetus are collected from amniotic fluid
Cells grown in lab
Karyotype produced to look for chromosome structure mutations
Explain how CVS is carried out
Foetal cells are collected from placenta
Karyotype instantly done from large sample of cells
What is a Karyotype
A Karyotype is a picture of a cells chromosomes. It is possible to see chromosome abnormalities
What stage of pregnancy can amniocentesis be carried out
14-16 weeks
What stage of pregnancy can CVS be carried out
8-10 weeks
How long does it take for amniocentesis results
3 weeks
How long does it take for CVS results
24 hours
Location cells collected amniocentesis
Amniotic fluid
Location cells collected CVS
Placenta
Is risk of miscarriage higher in CVS or amniocentesis
CVS
What is genetic counselling
Genetic counselling examines family trees and phenotypes to determine genotypes of all family members. This helps inform prospective parents the risk of passing on genetic diseases
What are all patterns of inheritance
Autosomal dominant
Autosomal recessive
Sex-linked
Incomplete dominance
Define autosomal
An autosomal gene is present on chromosome numbers 1-22. It is not present on the sex chromsomes X or Y.
Features of autosomal dominant
Affected person in every generation
Affects males just as much as females
Sufferers can be homozygous dominant or heterozygous
Healthy people are homozygous recessive
Example of autosomal dominant disease
Huntingtons disease
Features of autosomal recessive
Can skip a generation
Equal numbers of males and females affected
Sufferers are homozygous recessive
Carriers are heterozygous
Unaffected are homozygous dominant
Example of autosomal recessive disease
Cystic fibrosis
Define sex linked
A sex linked gene is present only on the X chromsome. Females have 2 x chromsomes, males have 1. Mutated genes tend to be recessive.
Features of sex linked
More males affected than females
Affected fathers cannot pass their conditions on to their sons
Genotypes written like XRxr (female) or XrY (male)
It can skip a generation
Unaffected males will have unaffected or carrier daughters (depending on mother)
Example of sex linked disease
Haemophilia
Define Incomplete dominance
Some alleles are not fully dominant or recessive. E.g. the genes that control flower colour in snapdragon plants, an allele for red (RR) and allele for white (WW) = RW (makes pink) this can be the same for some genetic diseases
Example of incomplete dominance disease
Sickle cell anemia
Features of incomplete dominance
Carriers (heterozygous) are partially affected
More carriers than sufferers
Sufferers homozygous for mutated gene
Unaffected homozygous for the normal gene
Males and females equally affected
What is postnatal screening
Some conditions need to be tested for immediately after birth, this is to ensure infant is not fed something or given medication that may be harmful to them.
What is PKU
One condition that is postnatal screened for is called PKU. It is a metabolic disorder where the body cannot break down phenylalanine, an amino acid. It is found in all proteins. If baby ingests too much protein eg I’m breast milk it can cause brain damage
What kind of condition is PKU and how is it inherited
PKU is an autosomal recessive condition
Both parents must be carriers to pass the condition on
It cannot be predicted by antenatal screening
