Which description best explains Watson and Crick's DNA model? DNA is a single–stranded molecule that has nitrogenous bases toward its exterior. DNA is a double helix made of two strands linked together with hydrogen bonds. DNA is a double helix that contains nitrogenous bases toward its exterior.

the reason the two sea urchins don't compete with each other for food, resources, etc. is because the urchins have adapted to the environment but they have also adapted to each other. this is most likely because the genes of the sea urchins.

a unit of heredity that is transferred from a parent to offspring and is held to determine some characteristic of the offspring.

i think the answer is a.keratin is the pigment responsible for skin color.

answeramino acids;