3. in chickens, the frizzle gene “f” controls the appearance of the feathers. a homozygous dominant chicken for the frizzle gene shows “extreme frizzle”, that is his feathers are extremely disrupted. the normal chicken is homozygous recessive and has undisrupted feathers. when a chicken with extreme frizzle is mated with a normal chicken, all of the offspring exhibit mild frizzle.

the oxygenated blood then leaves the lungs through pulmonary veins, which return it to the left heart, completing the pulmonary cycle. this blood then enters the left atrium, which pumps it through the mitral valve into the left ventricle. from the left ventricle, the blood passes through the aortic valve to the aorta.

deoxygenated blood leaves through the right ventricle through the pulmonary artery. from the right atrium, the blood is pumped through the tricuspid valve (or right atrioventricular valve), into the right ventricle.