Question

1. Clopidogrel is an antiplatelet drug, it prevents blood platelets from sticking together and

forming blood clots. This drug is given to prevent clot formation in individuals with a history of

stroke; heart attack; abnormal blood clot formation; or plaque buildup.

Clopidogrel resistance is a genetic condition in which the drug clopidogrel (Plavix) is less

effective in certain people. People with clopidogrel resistance who receive clopidogrel are at

risk of serious, sometimes fatal, complications if they have certain mutations in the CYP2C19

gene. The CYP2C19 gene codes for an enzyme that metabolizes clopidogrel and makes the drug

active in the human body.

People with clopidogrel resistance are called Poor metabolizers, Their body does not process

the drug and the drug is not effective in preventing blood clots. The mutation in the CYP2C19

gene that is responsible for the poor metabolizer phenotype and is referred to as the CYP2C19

*2 allele.

A different mutation can cause people to be rapid metabolizers. The CYP2C19 *17 is an allele

which has a mutation that leads to rapid metabolism of clopidogrel. These individuals process

the drug quickly and are at risk for increased bleeding because they cannot form blood clots.

*1 is the normal or “wild-type” form of the gene.

CYP219 has an autosomal recessive pattern of inheritance and follows the laws of Mendalian

genetics. (One copy of the gene is inherited form each parent, the combination of alleles results

in the person’s phenotype.)

Ex: *1/ *1 = normal metabolizer

*1/*2 = intermediate metabolizer

*2/*2 is a poor metabolizer

For reference:

*1 = normal 2C19 enzyme activity

*2 = no 2C19 enzyme activity

*17 = rapid 2C19 enzyme activity

P1 generation: Mother: *1/*2 x

Father: *1 /*17

Use the information above to answering the following questions.

A. What percent chance does this couple have for a child that is a normal metabolizer (by *1/*1

or *2/*17 genotype)?

B. What percent chance does this couple have for a child that is a rapid metabolizer?

C. What percent chance does this couple have for a child that is an intermediate metabolizer?

D. Draw the genotypes for the parents in a monohybrid cross if: 25% of the offspring are poor

metabolizers, 50% are intermediate metabolizers, and 25% are normal metabolizers.

Answer 1

Mother: *1/*2 x  Father: *1 /*17

Children: *1/*1, *1/*17, *2/*1, *2/*17

A. There will be 50% chance, this couple have for a child that is a normal metabolizer (by *1/*1 or *2/*17 genotype).

B. There will be 0% chance, this couple have for a child that is a rapid metabolizer (*17/*17).

C. There will be 25% chance, this couple have for a child that is an intermediate metabolizer (*2/*1).

D. 25% of the offspring are poor metabolizers (*2/*2)

50% are intermediate metabolizers (*1/*2)

25% are normal metabolizers (*1/ *1).

So, the genotypes for the parents would be: Mother: *1/*2 x  Father: *1 /*2.