The nucleus contains the chromosomes of the cell. The main genome of the organism is found in the nucleus. In humans, the nucleus holds 46 chromosomes, which contains about 25,000 genes. However, mitochondria have DNA of their own.The human mitochondrion has DNA in the form of plasmids, which are circular pieces of DNA. Mitochondrial genes encode for 13 proteins and 24 RNA molecules that are only found in the mitochondrion.he nucleus contains the chromosomes of the cell. The main genome of the organism is found in the nucleus. In humans, the nucleus holds 46 chromosomes, which contains about 25,000 genes. However, mitochondria have DNA of their own.
Print. The heart has two upper and two lower chambers. The upper chambers, the right and left atria, receive incoming blood. The lower chambers, the more muscular right and left ventricles, pump blood out of your heart.The heart valves, which keep blood flowing in the right direction, are gates at the chamber openings.he heart has two upper and two lower chambers. The upper chambers, the right and left atria, receive incoming blood.
The two chambers at the bottom of the heart are called ventricles. Their job is to squirt out the blood. In the middle of the heart there is a thick muscle called the septum that separates the left and the right side. The atria and ventricles work together.The atria fill with blood and when they are full they let the blood into the ventricles.When these ventricles pump the blood out of the heart, the atria fill up again and the whole process starts again. There are valves in the heart that make sure that the blood is pumped in the right direction.When the heart contracts, it pumps blood from its chambers into the body.he atria fill with blood and when they are full they let the blood into the ventricles. When these ventricles pump the blood out of the heart, the atria fill up again and the whole process starts again. There are valves in the heart that make sure that the blood is pumped in the right direction.