Congenital and inherited diseases

Question 1

Define: congential disease

Answer 1

present at birth

Question 2

define: genetic disease

Answer 2

caused by chromosome or gene defect

Question 3

define: inherited disease

Answer 3

passed from parent to offspring

Question 4

define teratogen

Answer 4

exposure that affects normal growth, structure or function of a developing embryo

Question 5

how does severity of congenital malformations impact life expectancy (reference major and minor)

Answer 5

1. minor defects may arise later in life
2. major defects are incompatible with life

Question 6

4 types of congenital malformation

Answer 6

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

Question 7

what is the difference between primary and secondary factors in realtion to congenital malformations

Answer 7

1. primary are genetic factors
2. secondary are environmental/external factors

Question 8

list examples of secondary factors (7)

Answer 8

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)

Question 9

explain what is meant by TORCH - list the 5 diseases included and how they impact the foetus

Answer 9

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

Question 10

what are the 3 most common congenital malformations

Answer 10

congential heart defects
neural tube defects
down syndrome

Question 11

list and describe the types of inherited diseases (4)

Answer 11

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)

Question 12

list the causes of chromosomal abnormalities (3)

Answer 12

non disjunction - too many on one side
translocation
deletion/duplication

Question 13

what are variations in sex chromosome usually linked to

Answer 13

reduced intelligence

Question 14

what effect does an extra Y chromosome have

Answer 14

extra Y’s do not impact the phenotype, only indicates male sex

Question 15

what effect does an extra X chromosome have

Answer 15

little effect on females but adversely effects masculine development

Question 16

how to autosomal abnormalities impact life

Answer 16

absence of autosomes are incompatible with life
partial loss may be compatible but leads to congenital disorders
gain causews abnormalities and most are leathal

Question 17

what disorder is caused by trisomy 13?

Answer 17

patau syndrome
causes eye, brain and circulatory defects, dont live more than a few months

Question 18

what disorder is caused by trisomy 18

Answer 18

edwards syndrome, dont live more than a few months

Question 19

how do mutation in mitochondrial DNA result in respriratory chain dysfunction

Answer 19

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)

Question 20

explain what is meant by residual function

Answer 20

mutation in which the protein still functions, but less well than the wild type

Question 21

what is the threshold model of disease and what are the two prominent types (MI)

Answer 21

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

Question 22

how does liability relate to disease

Answer 22

disease increase with increasing liability
genetic liabilities above a certain threshold results in abnormalities, especially if environmental influences are present

Question 23

what is the difference between predictive and diagnostic testing

Answer 23

Diagnostic: confirms diagnosis in affected child
predictive: testing of unaffected individuals

Question 24

what are the two possible outcomes of predicitve testing

Answer 24

1. identifying carriers
2. 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

Question 25

benefits of prenatal testing (3)

Answer 25

1. preparation for support after birth
2. prognosis and life expectancy
3. decision whether or not to continue pregnancy

Question 26

challenges of prenatal testing (4)

Answer 26

1. need to know disease causing mutation
2. religious/spiritual beliefs
3. risk to fetus associated with invasive procedures –> amniocentesis
4. does not guarantee a healthy baby