Genetic Variation

Question 1

isozymes

Answer 1

distinguishable proteins with the same or similar enzymatic activity

Question 2

isoforms

Answer 2

proteins with similar functional and/or structural properties, may be derived from genes at different loci or from alternative splicing or post-translational modification

Question 3

four possible consequences of multiple alleles at a locus

Answer 3

no phenotypic effect

contribute to the normal variation of a trait

affect disease susceptibility

directly disturb protein function and cause disease

Question 4

polymorphism

Answer 4

the occurence of two or more allelic traits in a population with frequencies of at least 1-2%

Question 5

single nucleotide polymorphisms

Answer 5

substitution of one base for another, may be conserved, occur every 100-200 base pair

heterozygosity occurs every 250-500 base pairs

an individual may be heterozygous at 6-12 million sites

Question 6

haptoglobin

Answer 6

synthesized in the liver and binds free hemoglobin

composed of alpha beta subunits joined by disulfide bonds

several polymorphisms of the alpha subunit

Question 7

peptidase

Answer 7

ubiquitous dipeptidase, illustrate a benign polymorphism in a dimeric protein

middle band indicates a type 2-1 hybrid dimer

Question 8

psudocholinesterase

Answer 8

a “benign variant that behaves as a disease susceptibility gene in certain circumstances

important for degrading certain drugs such as succinyl dicholine, the atypical form leads to prolonged paralysis because it cannot degrade the drug as fast

indidstinuishable electrophoretically but is inhibited less by the dibucaine inhibitor

Question 9

apolipoprotein-B

Answer 9

part of the cholesterol pathway, important for binding cholesterol

polymorphisms in the carboxy terminal at codons 3611 and 4154 have been identified, leads to 4 possible alleles and 10 possible genotypes

might lead to altered cholesterol metabolism and varying levels of cholesterol in the blood

Question 10

detecting polymorphisms

Answer 10

at the level of protein - electrophoretic mobility, Km, thermostability, and other biophysical properties

at the level of the gene - sequence change in an exon

at the level of the genome - SNPs, STRs (short tandem repeats such as microsatellties)