Which step happens first to a chromosome during cell division?
A. Nucleotides are added to each half of a DNA molecule.
B. A DNA molecule unwinds, exposing the bases on each half.
C. Each half of a DNA molecule acts as a template.
D. Two identical DNA molecules form.

Which of these statements best describes the st. lawrence seaway? the st. lawrence seaway connects the st. lawrence river with the arctic ocean. the st. lawrence seaway provides an important trading route between the u. s. and mexico. the st. lawrence seaway provides an important trading route for the u. s, but has little value for canada. the st. lawrence seaway connects the great lakes, the st. lawrence river, and the atlantic ocean.

Out of the seven main animal groups (fish, mammals, birds, insects, reptiles, amphibians, and arachnids), how many contain members with internal backbones? a. 5 b. 3 c. 7 d. 1

Aboy with an extra x chromosome probably has which of the following syndromes?