Individuals with down syndrome have an extra chromosome 21. this is an example of which type of chromosome disorder?

What are genotypes? what are phenotypes?

The unique structure of the neuron is dedicated to the efficient and rapid transmission of neural signals. the relationship between neurons, the spinal cord, and the brain constitutes an elaborate communication system throughout the human body. all but one of the functions listed below are a result of this interaction.

The distant ancestors of tigers may have had bodies without stripes. use the theory of natural selection to explain how tigers may have evolved to have stripes.