During an examination, a doctor hears fluttering in the first part of the heartbeat. this likely indicates a problem with which part of the heart?
the right and left atria

the right and left ventricles

the valves between the atria and the ventricles

the valves between the atria and the body

Spherocytosis is an inherited blood disease in which the erythrocytes (red blood cells) are spherical instead of biconcave. this condition is inherited in a dominant fashion, with sph- dominant to sph+. in people with spherocytosis, the spleen "reads" the spherical red blood cells as defective, and it removes them from the bloodstream, leading to anemia. the spleen in different people removes the spherical erythrocytes with different efficiencies. some people with spherical erythrocytes suffer severe anemia and some mild anemia, yet others have spleens that function so poorly there are no symptoms of anemia at all. when 2400 people with the genotype sph- sph+ were examined, it was found that 2250 had anemia of varying severity, but 150 had no symptoms. does this description of people with spherocytosis represent incomplete penetrance, variable expressivity, or both? explain your answer. (3 points)

How do nicotine and tobacco cause cancer? by decreasing blood-sugar levels by damaging or changing a cell's dna by increasing heart rate by increasing phlegm and mucous production

In which way does nicotine cause addiction? by stimulating the brain’s pleasure center by increasing blood-sugar levels by decreasing dopamine levels by reducing depression and anxiety