Unit 2 KA4 - ante and postnatal screening

Question 1

techniques an be carried out to monitor the health of the …….., ………… and …………

Answer 1

mother, developing fetus, and baby

Question 2

what is the meaning and purpose of antenatal screeening?

Answer 2

screening before birth to identify the risk of a disorder so further tests and a prenatal diagnosis can be offered

Question 3

give examples of antenatal screening

Answer 3

ultrasound imaging, blood and urine tests and diagnostic tests

Question 4

what is ultrasound imaging?

Answer 4

when an ultrasound scanner is held against pregnant women’s abdomen and picks up high frequency sounds that have bounced off the fetus
these are converted to an ultrasound image on a computer screen

Question 5

what are the 2 types of ultrasound screening and when are they carried out?

Answer 5

dating scan - 8-14 weeks

anomaly scan - 18-20 weeks

Question 6

why is the dating scan carried out?

Answer 6

to determine the stage of pregnancy and due date

used alongside tests for marker chemicals

Question 7

why is the anomaly scan carried out?

Answer 7

detects presence of serious physical abnormalities in the fetus e.g. spina bifida

Question 8

when and why are blood and urine tests carried out?

Answer 8

throughout pregnancy to monitor concentration of marker chemicals

Question 9

atypical chemical concentrations indicate a ……., so ………… ………… must take place

Answer 9

problem, diagnostic testing

Question 10

what leads to a false-positive result in a blood/urine test?

Answer 10

measuring a chemical at the wrong time since marker chemicals vary at different stages of pregnancy

Question 11

what is diagnostic testing?

Answer 11

definitive test that produces results used to establish if the fetus is suffering a specific condition/disorder

Question 12

in which cases is diagnostic testing offered to a pregnant woman?

Answer 12

• screening tests have shown a potential problem
• family history of genetic disorders
• she belongs to a high-risk group (e.g women over the age of 35)

Question 13

give examples of diagnostic testing?

Answer 13

amniocentesis and chorionic villus sampling (CVS)

Question 14

what is a karyotype and where are they produced from?

Answer 14

shows an individual’s chromosomes arranged as homologous pairs
produced from fetal cells which have been cultured

Question 15

what are karyotypes used for?

Answer 15

to diagnose a range of conditions

Question 16

where are fetal cells obtained from?

Answer 16

amniocentesis and CVS

Question 17

when is amnio and CVS carried out?

Answer 17

amnio - 14-16 weeks

CVS - 8 weeks

Question 18

describe the process of amniocentesis

Answer 18

amniotic fluid containing fetal cells are withdrawn

they are cultured, stained, and examined under a microscope to create the karyotype

Question 19

give an advantage and disadvantage of amniocentesis

Answer 19

advantage - chromosome abnormalities can be detected

disadvantage - risk of miscarriage

Question 20

describe the process of CVS

Answer 20

a tiny sample of placental cells are taken using a fine tube inserted into the mother’s reproductive tract
the cells are cultured and used for karyotyping

Question 21

give an advantage and disadvantage of CVS

Answer 21

advantage - can be carried out at 8 weeks whereas amnio is 14-16 weeks
disadvantage - higher risk of miscarriage than amnio

Question 22

a family tree looking at ………………. is constructed by a ……………
analysis to spot …….. and ……… chances of parents producing offspring with …………..

Answer 22

genetic conditions/disorders, genetic counsellor, patterns, predict, genetic disease

Question 23

once …….. of family members are known, the …….. can be worked out

Answer 23

phenotypes, genotypes

Question 24

X and Y chromosomes are called………. and all other chromosomes are called……..

Answer 24

sex chromosomes, autosomes

Question 25

give an example of autosomal recessive inheritance

Answer 25

cystic fibrosis

Question 26

what patterns can be spotted by a geneticist in autosomal recessive inheritance?

Answer 26

- the trait is expressed rarely - the trait may skip generations - the trait is expressed in some of the offspring of a consanguineous marriage - males and females are affected in approx. equal numbers

Question 27

what are the genotypes of sufferers and non-sufferers in autosomal recessive inheritance?

Answer 27

sufferers - homozygous recessive (ff) | non-sufferes - homozygous dominant (FF) or heterozygous (Ff)

Question 28

give an example of autosomal dominant inheritance

Answer 28

huntington's disease

Question 29

what patterns can be spotted by a geneticist in autosomal dominant inheritance?

Answer 29

- the trait is expressed in every generation - each sufferer of the trait has an affected parent - males and females are affected in approx. equal numbers

Question 30

what are the genotypes of sufferers and non-sufferers in autosomal dominant inheritance?

Answer 30

non-sufferers - homozygous recessive (hh) | sufferers - homozygous dominant (HH) or heterozygous (Hh)

Question 31

give an example of autosomal incomplete inheritance

Answer 31

sickle cell disease

Question 32

what patterns can be spotted by a geneticist in autosomal incomplete inheritance?

Answer 32

- the fully expressed form occurs rarely - partly expressed form occurs more frequently - each sufferer of the fully expressed form has 2 parents who suffer from the partly expressed form - males and females are affected in approx. equal numbers

Question 33

what are the genotypes of sufferers (partly expressed and fully expressed) and non-sufferers in autosomal incomplete inheritance?

Answer 33

sufferers (fully expressed) - homozygous for the other incompletely dominant alleles (SS) sufferers (partly expressed) - heterozygous for the two alleles (HS) non-sufferers - homozygous for one incompletely dominant allele (HH)

Question 34

give an example of sex-linked recessive traits

Answer 34

hemophilia

Question 35

what patterns can be spotted by a geneticist in sex-linked recessive traits?

Answer 35

- more males than females are affected - none of the sons of an affected male show the trait - some grandsons of an affected male show the trait

Question 36

what are the genotypes of sufferers and non-sufferers for sex-linked recessive traits?

Answer 36

sufferers are homozygous recessive | non-sufferers are homozygous dominant

Question 37

why and why is postnatal screening carried out?

Answer 37

after birth when the baby is a few days old to test for metabolic disorders

Question 38

what is phenylketonuria (PKU) caused by?

Answer 38

a subsitution mutation which distrupts the metabolic pathway that converts phenylalanine into tyrosine a the enzymes that catalyses this conversion is non functioning

Question 39

how are newborn babies screened for PKU and what steps are taken if they are a sufferer?

Answer 39

by having their blood tested for the presence of excess phenylalanine PKU sufferers are put on a restricted diet to limit amount of phenylalanine