Why do red blood cells have no nucleus?

Why reason best illustrates why hershey and chase chose to use viruses in their experiment?

Which of these is not an example of molecular homology? 1. use of dna and rna as genetic material 2.use of glycolysis as the first step in cellular respiration in both plants and animals 3. the lack of an igf-1 gene in prokaryotes 4. the use of aldolase b to break down fructose in bacteria, plants and animals

The part of the eye that closes and opens to let light in is .