If someone is predisposed to a disease, they are more likely to contract the disease due to
a. lifestyle choices
b. heredity
c. random chance
d. factors other than heredity or lifestyle

The best answer is B.

If a person is predisposed to a particular disease, they are most likely to catch that disease due to heredity. This is called genetic predisposition.

Genetic predisposition sometimes also called genetic susceptibility, is an increased likelihood of developing a particular disease based on  person's genetic makeup.

Genetic predisposition results from some specific genetic variations that are often inherited from parents. These genetic changes contribute to the development of a disease but do not cause it.  Some predisposed  people will never get the disease while others with same predisposition will get it, even within the same family.

1) gene flow

- it is described as the transfer of genes from one population to another population so that frequency of gene is increased.

-a zebra migrates to join a different herd of zebras.

2) natural selection

- a mechanism of evolutionary change in which individuals with advantageous traits survive and reproduce whereas the others ( those that can not adapt) eliminate from the population.

-competition for sunlight leads to taller trees.

3) mutation

- permanent change in the nucleotide sequence of dna ( genetic material) that could have harmful or useful consequences.

-the dna of a snake changes to make its venom stronger.

4) genetic drift - it is a random phenomenon ( that occurs by chance such as fire) that results in change in the gene frequency in a small population.    

-a grassfire randomly sweeps through a population of buffalo and kills most of the animals.

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