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.
1 The upper chambers â called the right atrium and the left atrium â collect blood flowing in from the body and in from the lungs. 2  The lower chambers â called ventricles â collect blood before it gets pumped forcefully out. 3  The right ventricle pumps out to the lungs.