Roles of genetic and environmental factors in disease causation

Question 1

Why disease does not develop in everybody exposed to an environment risk factor?

Answer 1

Humans differ from one another and some people will be more susceptible to a disease than others because of their genetic makeup

Question 2

Genetic markers

Answer 2

a genetic marker is a gene , DNA sequence or gene product that is associated with a specific condition or risk of obtaining a specific condition that can be tested for in a lab

Question 3

Methods used to test for and evaluate genetic markers

Answer 3

Microarrays: examine level of expression of a large no. of genes simultaneously and not just what genes are present in and individual. Overexpression or no expression may contribute to disease
HLA (human leukocyte antigen)

Question 4

Age of onset of disease

Answer 4

When a disease occurs both genetic and non genetic forms, the genetic form tends to develop in patients at a much earlier age than the non-genetic form. This is because non genetic diseases require a build-up of environmental exposures over time and therefore diseases take longer to develop .

Question 5

Family studies

Answer 5

Certain diseases run in certain families and may be a result of genetic or environmental factors

Question 6

Family pedigree

Answer 6

sheds light on how a disease is passed from generation to generation.
And can be used to estimate influence of genetic traits on the cause of disease

Question 7

Spousal concordance

Answer 7

Both husband and wife have disease

environmental factors are most likely the cause

Question 8

Types of twins

Answer 8

Monozygotic ( identical) twins- come from the same fertilized ovum therefore genetically identical
dizygotic (fraternal)twins- come from two separate ova and are the same as ordinary siblings that happen to develop in the uterus at the same time

Question 9

Occurrence of disease in the different types of twins

Answer 9

Monozygotic twins- both may have or neither may have disease (concordant of the disease) or only one twin may have the disease while the other doesn’t (discordant)
If disease is genetic we would expect less concordance for dizygotic twins than for monozygotic twins

Question 10

Big problem when working with twin concordance

Answer 10

Publication bias- it is more likely that a researcher will publish data when both twins have a rare disease than if they observe only one twin with a disease

Question 11

Adoption studies

Answer 11

Monozygotic twins normally grew up in the same environment. This makes it difficult to determine what contribution the environment and genetic factors made.
To determine whether disease is primarily genetic or environmental in origin.

Question 12

Migrants are studied the same way as

Answer 12

Adoptees

Question 13

If no. of cases of a disease increase or decrease significantly over time then it can be assumed that?

Answer 13

Environmental factors are most likely the cause of the disease. This is because the overall genetic characteristics of the human population do not typically change over short periods.