parkinson's disease is caused by degeneration of a pathway of neurons that releases which neurotransmitter?

Which statement best describes the relationship between an allele and a gene? question 1 a. an allele is a variation of a gene that can be expressed as a phenotype. b. an allele is the part of a gene that attaches to messenger rna molecules. c. an allele is a segment of a dna molecule that controls replication of a gene.

Cells are adapted to preform specific functions. which of the following terms refers to this capability?

Describe the two types of vascular tissue