What type of mutation causes sickle-cell anemia? -nonsense mutation
-chromosomal mutation
-silent mutation
-missense mutation

Sickle cell anemia is caused by a missense mutation.

Explanation:

In sickle cell anemia, a change in the DNA nucleotide sequence is observed, where adenine is substituted by thymine, whose expression is the change in the sequence of amino acids in β-globin, with valine being incorporated instead of glutamic acid. This constitutes a mutation of the missense type.

Missense mutations are characterized by the substitution of one nucleotide by another in the DNA sequence —a point mutation— whose consequence is reflected in the transcription and substitution of one amino acid by another in a protein, whose structure or function will be altered.

The change from glutamic acid to valine in β-globin causes an altered hemoglobin, giving the abnormal erythrocytes observed in sickle cell disease.

when atoms of different types of elements join together, they make molecules called compounds. water consists of compound molecules made up of 2 hydrogen atoms and 1 oxygen atom. this is why it's called h2o. water will always have 2 times the number of hydrogen atoms as oxygen atoms.

the framers of the constitution insisted that federal judges be nominated instead of elected due to their desire to have judges above the shifting whims of the masses.

the hope, whether achieved or not, was that federal judges would only be beholden to the law and that by not having judges be elected, they would be protected if that law dictated an outcome that ran counter to popular opinion.