Why do doctors check for swollen lymph nodes?

a. bacteria and viruses mostly attack the lymph nodes.

b. memory cells are stored in the lymph nodes

c. it is impossible to immunize the lymph nodes

d. lymph nodes are the site of white blood cell production

Covalent bonds are formed between metals and boiling points true or false

Name the glands associated with human digestive system

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.