Homozygous organism

The genetic constitution of an organism, which it has inherited from its parents. The genotype refers to the particular combination of alleles at specified loci present in an organism homozygous individuals have identical alleles and heterozygous individuals have different alleles. 

Dominant. Describing an allele the phenotype of which is expressed regardless of whether the organism is homozygous or heterozygous for that allele. 

Homozygous. Describing an organism (a homozygote) that carries two identical alleles for a given gene. 

The genetic makeup of a person (or other organism) is the genotype. If two alleles are alike (RR or rr), the person is homozygous for the trait in question. If they are different (Rr), the person is heterozygous. The manifestation of the trait itself, in this case hair color, is the phenotype. Two persons, one with Rr and the other with RR, have different genotypes, but the same phenotype. 

LDL, the major cholesterol transport lipoprotein, having virtually only apolipoprotein B-lOO, is mostly derived from VLDL catabolism and cellular synthesis. When fasting and when normal subjects are on low-fat intake, most cholesterol is synthesized and used in the extrahepatic organs, whereas most of the cholesterol carried by LDL is taken up by the liver for catabolism. In patients with homozygous familial hypercholesterolemia, enhanced synthesis of LDL may occur because LDL clearance is reduced as a consequence... 

Recessive Gene. An allele having no effect on the organism unless homozygous. 

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