Can you accurately determine an genotype by observing its phenotype?

Yes. We can determine an genotype by observing it's phenotype by a "Test Cross".

If we cross between Homozygous recessive plant with dominant one, we can tell from the results of cross, that dominant individual is Homozygous or Heterozygous,.

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1) the mayans built pyramids just like the egyptians. the mayans also used hieroglyphics like them.2) power was passed down by family. for example, if the father dies, the son would be the next king.3)they both built pyramids for their structures.4)the main crop for the mayans was maize.5)they also grew manioc, beans,  squash,  amaranth, and chile peppers.