Congenital and inherited diseases Flashcards
Define: congential disease
present at birth
define: genetic disease
caused by chromosome or gene defect
define: inherited disease
passed from parent to offspring
define teratogen
exposure that affects normal growth, structure or function of a developing embryo
how does severity of congenital malformations impact life expectancy (reference major and minor)
- minor defects may arise later in life
- major defects are incompatible with life
4 types of congenital malformation
syndrome: arises from single factor e.g. down syndrome
sequences: single initiating event leading to secondary events e.g. Pierre robin sequence
disruptions: external interteruption to development e.g. thalidomide
dysplasia: structural defects of specific tissues e.g. achondroplasia
what is the difference between primary and secondary factors in realtion to congenital malformations
- primary are genetic factors
- secondary are environmental/external factors
list examples of secondary factors (7)
Infectious agents (e.g. TORCH)
Chemical agents (e.g. therapeutic and recreational drugs)
Physical agents (e.g. ionising radiation)
Vascular disruptions (e.g. subclavian artery disruption)
Mechanical causes (e.g. amniotic bands, oligohydramnios)
Dietary deficiency (e.g. folate)
Maternal disorders (e.g. diabetes, phenylketonuria)
explain what is meant by TORCH - list the 5 diseases included and how they impact the foetus
group of infectious diseases that cause congenital malformations including
1. toxoplasmosis
2. other e.g. HIV
3. Rubella
4. Cytomegalovirus
5. Herpes simplex
the mother contracts the disease and passes it across the placenta. the mother is asymptomatic but the foetus has an underdeveloped immune system and so feels its effects. can lead to malformation
what are the 3 most common congenital malformations
congential heart defects
neural tube defects
down syndrome
list and describe the types of inherited diseases (4)
Chromosomal (copy number)
monogenic (mutation in one gene sufficient enough for disease)
polygenic (multiple genes contribute to phenotype –> each has a small effect)
susceptibility (gene and environment)
list the causes of chromosomal abnormalities (3)
non disjunction - too many on one side
translocation
deletion/duplication
what are variations in sex chromosome usually linked to
reduced intelligence
what effect does an extra Y chromosome have
extra Y’s do not impact the phenotype, only indicates male sex
what effect does an extra X chromosome have
little effect on females but adversely effects masculine development
how to autosomal abnormalities impact life
absence of autosomes are incompatible with life
partial loss may be compatible but leads to congenital disorders
gain causews abnormalities and most are leathal
what disorder is caused by trisomy 13?
patau syndrome
causes eye, brain and circulatory defects, dont live more than a few months
what disorder is caused by trisomy 18
edwards syndrome, dont live more than a few months
how do mutation in mitochondrial DNA result in respriratory chain dysfunction
mtDNA encodes proteins required for normal respiratory chain function
mutations result in dysfunction of energy production by. mitochondria
typically have prominent neurological and myopathic features (due to high energy requirement of tissues)
explain what is meant by residual function
mutation in which the protein still functions, but less well than the wild type
what is the threshold model of disease and what are the two prominent types (MI)
all the factors which influence the development of a multifactorial disorder are referred to as liability
genetic liability: adverse genetic changes
environmental liability: adverse environmental conditions
how does liability relate to disease
disease increase with increasing liability
genetic liabilities above a certain threshold results in abnormalities, especially if environmental influences are present
what is the difference between predictive and diagnostic testing
Diagnostic: confirms diagnosis in affected child
predictive: testing of unaffected individuals
what are the two possible outcomes of predicitve testing
- identifying carriers
- prenatal/pre-implantation to predict wheter a child will be born with/develop disease
- scans may show evidence of structural abnormality
- some disorders cannot be tested for e.g. non-syndromes and cancer susceptibility
benefits of prenatal testing (3)
- preparation for support after birth
- prognosis and life expectancy
- decision whether or not to continue pregnancy
challenges of prenatal testing (4)
- need to know disease causing mutation
- religious/spiritual beliefs
- risk to fetus associated with invasive procedures –> amniocentesis
- does not guarantee a healthy baby
