Question

A group of geneticists are interested in identifying genes that may play a role in susceptibility to asthma. They study the inheritance of genetic markers in a series of families that have two or more asthmatic children. They find an association between the presence or absence of asthma and a genetic marker on the short arm of chromosome 20 and calculate a LOD score of 2 for this association.

What does this LOD score indicate about genes that may influence asthma?
a. It shows that the probability of the marker being linked to a gene for asthma susceptibility is 100 times less than the probability that there is no linkage.
b. It shows that the probability that this marker is linked to a gene for asthma susceptibility is two times greater than if there is no linkage.
c. It indicates that this genetic marker likely causes susceptibility to asthma.
d. It shows that the probability that this marker is linked to a gene for asthma susceptibility is 100 times greater than the probability that there is no linkage.
e. It shows that marker has no relationship to susceptibility to asthma.

Answer 1

The correct answer is D.

Step-by-step explanation:

LOD score means logarithm of the Odds and is a statistical test used in genetics. It is used to establish genetic linkage, to establish if a genetic marker is related to a particular disease or trait.

By convention, a LOD score of 3 establishes genetic linkage, it means 1000:1 likelihood. If the score is 2, it establishes 100:1 likelihood.

On the other hand, a LOD score of -2 discards genetic linkage.

The formula for LOD score is = Log 10 (Odds ratio)

Odds ratio (OR) establishes the chances of occurrence of an event (outcome) when exposed to a determine factor under study.

OR=
`(exposed cases with outcome/exposed cases without outcome)/(Not exposed cases with outcome/not exposed cases without outcome)`

If the OR is greater than 1, means that the outcome is related to exposure.

If it is lower than 1, the outcome is not related to exposure.

If it is 1, the exposure does not influence the outcome.