In familial hypercholesterolemia, individuals homozygous for the allele causing the disorder completely lack receptors on liver cells that take up cholesterol from the blood stream. heterozygotes have one-half the number of receptors while individuals homozygous for the normal allele are phenotypically normal. this is an example of

a) epistasis
b) incomplete dominance
c) complete dominance
d)codominance

The correct answer is option B, incomplete dominance

In the case of incomplete dominance, the allels of the two individuals that are cross do not produce either of their traits but results into a new individual with a different genotype and phenotype. For example if red and white flowers are crossed, pink offspring’s are produced.  

Here in this  case the heterozygotic parent cell has 50% of allel expressing the presence of receptors while homozygous lack receptor on liver cells that take up cholesterol from the blood stream and a cross between them produces homozygous , phenotypically normal individuals.  

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the sugar-phosphate backbone forms the structural framework of nucleic acids, including dna and rna. this backbone is composed of alternating sugar and phosphate groups, and defines directionality of the molecule.