Genetic and Environmental Causes of Disease

Question 1

What are the four main causes of disease?

Answer 1

1- Genetic
2- Environmental
3- Combination (multi-factorial)
4- Unknown

Question 2

How can the cause of diseases be identified?

Answer 2

1- Laboratory studies
2- Family studies
3- Epidemiology

Question 3

What is heritability?

Answer 3

A statistic which estimates the extent to which observed differences are caused by genes.

Question 4

What factors could lead to traits running in families?

Answer 4

1- Genes
2- Social learning or modeling
3- Operant conditioning (reward-based learning, positive/negative reinforcement and punishment)
4- Chance

Question 5

What heritable trait can change across generations?

Answer 5

Height

Question 6

What highly heritable conditions are easily modified?

Answer 6

1- Vision

2- Mental retardation due to Phenylketonuria (PKU)

Question 7

What interventions can heritable conditions respond to?

Answer 7

1- Drug intervention
2- Social intervention
3- Behavioural intervention

Question 8

How is heritabililty measured?

Answer 8

1- Family studies
2- Twin studies
3- Adoption studies
4- Migrant studies

Question 9

What factors do mono zygotic twins share?

Answer 9

1- Genes

2- Environment

Question 10

What factors do dizygotic twins share?

Answer 10

1- Environment

2- Same amount of genetic info as any other sibling

Question 11

In twin studies conducted to see if IQ is heritable, what problems may affect the results?

Answer 11

1- Monozygotic twins share their environment more than dizygotic twins due to being more encouraged to spent time together
2- Monozygotic twins may not have shared the same uterine environment due to varying concentrations of amniotic fluid cells

Question 12

How are phenotypes quantified?

Answer 12

Phenotype = genes + environment + (genes * environment)

Question 13

How is heritability quantified?

Answer 13

H2= Vg/Vg+Ve+V(g*e)

Question 14

What four factors or types of disease can be influenced by the environment?

Answer 14

1- Infection
2- Injury from chemical agents
3- Injury from physical agents
4- Behaviour

Question 15

What are the seven infectious agents?

Answer 15

1- Bacteria
2- Viruses
3- Fungi
4- Yeast
5- Protozoa
6- Parasites
7- Prions

Question 16

What are prions?

Answer 16

1- Proteins that replicate

2- E.g. mad cow disease or Creutzfeldt-Jakob disease in humans

Question 17

What is viral tropism?

Answer 17

A virus which will only infect a host if it has the right receptors, cell types, or environment.

Question 18

What are the seven modes of transmission?

Answer 18

1- Droplet (droplets from cough or sneeze)
2- Faeco-oral (fecal particles enter oral cavity)
3- Venereal (STI)
4- Blood
5- Water
6- Food
7- Vectors/fomites (inanimate vector e.g. touching a public phone)

Question 19

What are the four types of transmission?

Answer 19

1- Horizontal (individuals of same generation)
2- Vertical (across generations)
3- Zoonoses (from animals to humans)
4- Nosocomial (healthcare transmitted infections)

Question 20

What chemical agents can lead to disease?

Answer 20

1- Smoking
2- Alcohol
3- Drugs
4- Dust 
5- Food

Question 21

What diseases are associated with smoking?

Answer 21

1- Mutagenic- cancer
2- Inflammation- chronic obstructive pulmonary disease (COPD)
3- Nicotine receptors- increased blood pressure and heart rate
4- Endothelial damage
5- Carbon monoxide levels- intrauterine growth retardation

Question 22

What are the benefits of alcohol?

Answer 22

In small amounts, alcohol can reduce the risk of heart disease

Question 23

What can large doses of alcohol lead to?

Answer 23

Cirrhosis (chronic disease of liver due to increased scar tissue)

Question 24

The metabolism of alcohol leads to what consequences which underlie disease?

Answer 24

1- Acetaldehyde- carcinogenesis
2- Increased oestrogen levels
3- Decreased NAD levels alters lipid metabolism
4- Reactive oxygen damages lipid membranes
5- Decreased vitamin B levels
6- Depressed CNS function
7- Teratogenic (affects development of embryo)

Question 25

What conditions can be caused by dust?

Answer 25

1- Asbestos can cause mesothelioma
2- Coal dust can cause pneumoconiosis (inflammation, fibrosis and sometimes necrosis of the lungs)
3- Asthma
4- Hayfever

Question 26

What conditions can be caused by drugs?

Answer 26

1- Therapeutic drugs may have adverse side-effects

2- Recreational drugs may gradually damage body and bodily function

Question 27

How can food affect the body adversely?

Answer 27

1- Unhealthy diet

2- Sudden change in diet

Question 28

What are the different types of injury from physical agents?

Answer 28

1- Mechanical injury (trauma)
2- Thermal injury
3- Radiation

Question 29

What are the types of thermal injury?

Answer 29

1- Hypothermia
2- Fever (pyrexia)
3- Burns

Question 30

What are the types of radiation that may lead to injury?

Answer 30

1- Ionising

2- Non-ionising (UV lights)

Question 31

What is the Hardy-Weinberg principle?

Answer 31

Allele and genotype frequencies will remain constant from one generation to another in the absence of environmental factors (this is not always true!)

Question 32

Describe the balance between the risk of SCA and the protection that it provides against malaria

Answer 32

Hb-A normal blood cells, Hb-S sickle cells
1- Normal blood cell (Hb-A, Hb-A): no SCA but die from malaria
2- Sickle cell anaemia (Hb-S, Hb-S): resistant to malaria but SCA may be fatal
3- Heterozygotes (Hb-A, Hb-S): Blood has some normal cells and some sickle cells, more restistant to malaria. This has the most survival advantage.