Fetal Abnormality Flashcards
Human chromosome recognition methods
- banding patterns with specific stains
- length
- position of centromere
function of telomere
- protects end of the DNA
- prevents chromosomes from sticking together during division
types of aneuploidy
- Down’s Syndrome (trisomy 21) = [47 XY +21]
- Edward Syndrome (trisomy 18)
= [47 XY +18] - patau syndrome (trisomy 13)
= [47 XX +13]
X-chromosome disorders
- 45 X Turner syndrome
- 47 XXX Triple syndrome
- 47 XXY Klinefelter syndrome
What is robersonian translocation
diagram
- Philadelphia syndrom
- translocation of 9 and 22
- forms oncogene
- Two acrocentric chromosomes stuck end to end
different elements of pharmacokinetics
Liberation
• Particle size and formulation
Absorption
• Bioavailability of the drug, route of administration, barriers
Distribution
• Barriers and volume of distribution
Metabolism
• Clearance, drug interactions
Excretion
• Clearance, routes of elimination
What is bioavailability?
how much of the drug is available for use (decreased bioavailability = decreased drug reaching target tissue = decreased pharmacological effect)
what are the factors that affect distribution
- Degree of drug ionisation
- Lipid solubility
- pH of compartments
- Cardiac output and blood flow
- Capillary permeability
- Plasma protein binding
What are the two phases of metabolism
phase I:
- functionalisation (add/reveal a functional group) - key enzyme: cytochrome C
- products often more reactive
- generally oxidation, reduction or hydrolysis
phase II: conjugation (sulfate or glucuronide conjugation) –> make it more hydrophilic
define clearance
clearance = volume of the plasma cleared of the drug per unit time
define sensitivity
how well the test picks up having the disease
no. of results where disease detected in people w/disease/ no. of people with the disease
define specificity
how well the test detects not having the disease
no. of ‘normal’ results where the disease is not detected in people without the disease / no of people without the disease
Down’s syndrome screening
two stages to testing:
- screening test to find out if the baby has a high or low chance of having downs (offered up to 20 weeks)
- Diagnostic test to confirm whether baby has it (offered if screening showed high chance)
which screening tests are used
less than 14 weeks: blood test and nuchal translucency
14-20 weeks: blood tests only
What are the diagnostic tests
- transabdominal CVS - needle inserted into placenta
- transcervical CVS - small tube/forceps inserted through cervis
or
amniocentesis
Describe the phases of Meiosis I and II
Prophase I:
homologous chromosomes pair and form synapses
Prometaphase I:
The nuclear membrane disappears. One kinetochore forms per chromosome rather than one per chromatid, and the chromosomes attached to spindle fibers begin to move.
Metaphase I:
- two chromosomes (four chromatids) align at the metaphase plate
- (50-50 chance for the daughter cells to get either the mother’s or father’s homologue for each chromosome.)
Anaphase I:
Chromosomes, each with two chromatids, move to separate poles. = haploid daughter cells
Telophase I:
Nuclear envelopes may reform, or the cell may quickly start meiosis II.
Cytokinesis
What are balanced and unbalances chromosome rearrangement
Balanced: all the chromosomal material is present
Unbalanced: extra or missing chromosomal material. Usually 1 or 3 copies of some of the genome
What are the different oral routes of administration?
Buccal / sublingual mucosa
– Direct absorption into bloodstream
– Avoids first pass metabolism
– Not ideal surface for absorption
Small intestine
– Main site of drug absorption
– Large surface area, more neutral pH
Large intestine / colon
– Poor absorption, long transit times
Rectal mucosa
– Direct to systemic circulation
What are the ways that small molecules cross the cell membrane?
- diffusion through lipid
- diffusion through aqueous channel
. carrier - pinocytosis
Hydrophilic and lipophilic drug solubility
Hydrophilic drugs are soluble in aqueous, polar media.
Lipophilic drugs are soluble in fats and non-polar solutions.
Where are the sites of metabolism?
– Gut lumen – Gut wall – Plasma – Lungs – Kidneys – Nerves – Liver
Cytochrome P450 enzymes functions
- Biosynthesis of steroids, fatty acids and bile acids
* Metabolism of endogenous and exogenous substrates
what are the factors that can affect metabolism?
Age
Genetic variation
Disease
Other medication
Process of drug elimination
Drugs are eliminated either unchanged or as metabolites
• Hydrophilic drugs eliminated more readily than lipophilic drugs — Except the lungs
The kidneys are the most important organs involved in the elimination of drugs and their metabolites
what are the different methods of transmission of organisms?
Person-person contact Through food Contaminated waste water Insects Fomites
What are the three views about the status of the foetus?
- It is a human being from the time of conception
- It is a human being from the time of live birth
- It is a human being from some other time
Areas where the rights and interests of an adult woman outweigh those of a foetus
Abortion
Assisted reproduction
Pre-implantation genetic diagnosis
What were the legislations that controlled abortion in the 20th century?
- Offences Against the Person Act 1861 made performing an abortion or trying to self-abort carried a sentence of life imprisonment.
- Abortion Act 1967 made abortion legal in England, Scotland and Wales up to 28 weeks gestation
- Human Embryology and Fertilisation Act 1990 reduced term to 24 weeks gestation
The terms of abortion
• Two registered medical practitioners
• The pregnancy has not exceeded its twenty-fourth week and risk of
injury to the physical or mental health of the pregnant woman or any
existing children of her family; or
• Necessary to prevent grave permanent injury to the physical or
mental health of the pregnant woman; or
• Continuance of the pregnancy would involve risk to the life of the
pregnant woman; or
• Substantial risk that if the child were born it would suffer from such
physical or mental abnormalities as to be seriously handicapped.
What are the ethical considerations in screening for Down’s Syndrome?
Non-maleficence Beneficence Health maximisation Efficiency Respect for autonomy Justice
What are the potential benefits and harms of screening?
Benefits: • Reduced disease incidence (?) • Reduced disease mortality • Earlier, less radical treatment • Cost-effective • Overall population benefit
Harms: • False reassurance • Over-investigation and treatment • Anxiety • Longer period of morbidity with unaltered prognosis • Harm from screening test • Opportunity costs • Increased health inequalities
What are the challenges with optimising coverage?
- Change of address
- Migrants
- Travellers
- Prisoners
- Students
- Trafficked people
What could cause inequalities in terms of how screening programmes are run?
- Identifying and inviting screening cohort
- Acceptability of the test
- Failure to make reasonable adjustments
- Poor communication about the test results or the next steps in the programme
- Prejudice leading to poor care
what are the challenges with optimising uptake?
- Communication
- Health literacy
- Deprivation
- Accessibility
- Vulnerable groups
- Minority ethnic groups
