Allele

Allele and Cytochromes

1. ALLELE Saurabh kumar m.s. ( pHarm. ) NIPER, MOHALI, INDIA

2. ALLELE An allele is one of two or more versions of a gene. An individual inherits two alleles for each gene, one from each parent. If the two alleles are the same, the individual is homozygous for that gene. If the alleles are different, the individual is heterozygous.

3. MANIFESTATION Apparently healthy individuals can, for a number of reasons, carry many disadvantageous variants without showing any obvious ill effects: they might carry a single disease allele for a severe high-penetrance recessive disorder that requires two alleles to manifest the disease phenotype

4. GENETICS OF SCD

5. LETHAL ALLELES Genes which result in viability reduction of individual or become a cause for death of individuals carrying them. TWO TYPES RECESSIVE LETHAL ALLELES: RECESSSIVE LETHAL GENES CAN CODE FOE EITHER DOMINANT OR RECESSIVE TRAITS, BUT THEY DO NOT ACTUALLY CAUSE DEATH UNLESS AN ORGANISM CARRIES TWO COPIES OF THE LETHAL ALLELE.

6. RECESSIVE LEHAL ALLELES

7. Dominant lethal genes are expresses in both homozygotes and heterozygotes. But how can alleles like this be passed from one generation to next if they cause death? HUNTINGTON’S DISEASE: BECAUSE THE ONSET OF THIS DISEASE IS SLOW, INDIVIDUAL CARRYING THE ALLELE CAN PASS IT ON TO THEIR OFFSPRING. THIS ALLOWS THE ALLELE TO BE MAINTAINED IN THE POPULATION. DOMINANT LEHAL ALLELES

8. WHEN MORE THAN TWO DIFFERENT FORM OF GIVEN GENE EXIST IN A SPECIES THEY ARE CALLED AS MULTIPLE ALLELE. EX: BLOOD GROUP (ABO) IN HUMAN. FOR THE ABO GENE, THE THREE ALLELES ARE THE  I A I B AND i alleles. MULTIPLE ALLELE

9. Cytochromes P450 (CYP) are a major source of variability in drug pharmacokinetics and response Of 57 putatively functional human CYPs only about a dozen enzymes, belonging to the CYP1, 2, and 3 families , are responsible for the biotransformation of most foreign substances including 70–80% of all drugs in clinical use . poor metabolizer refers to homozygous or compound heterozygous carriers of alleles with complete lack of function (null allele). CYTOCHROMES P450

10. extensive metabolizer (EM) refers to the normal phenotype, usually representing the major proportion of the population. intermediate metabolizers (IM) carry only one normal or functionally deficient allele, resulting in impaired drug oxidation capacity. Severe loss-of-function alleles and functional gene duplications are rare among CYPs 1A1, 1A2, 2C8, 2E1, 2J2, and 3A4.