Which statements explain the gas exchange that happens at the alveoli?

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.

Which of the organisms listed below performs nitrogen fixation? a. legumes b. plants c. bacteria d. fungi

Give an example of a trait that is controlled by more than one gene.