Dna Information and Courses from MediaLab, Inc.

The proviral DNA provides genetic coding that instructs cellular enzymes to construct new HIV genomes, capsid proteins, and reverse transcriptase molecules.All of these are assembled near the edge of the host cell.

The double-stranded DNA molecule now migrates to the nucleus of its host cell. Once it reaches the nucleus, a viral enzyme called integrase joins the replicated HIV DNA to the cell's DNA. The viral DNA now becomes one of the cell's chromosomes and is called a provirus. At this point an individual is infected with and is a carrier of HIV but does not have AIDS.

Once the capsid and p24 and p17 have been stripped away, an enzyme complex known as reverse transcriptase is released.One of the enzymes in this complex is DNA polymerase. It synthesizes a single-stranded DNA copy using one of the HIV-RNA molecules as a template.Another enzyme in this complex, called ribonuclease, then destroys the original RNA molecules while the DNA polymerase synthesizes another single-stranded DNA molecule, this time using the first DNA copy as the template.The result is a double-stranded DNA molecule.

Several erythrocyte abnormalities are present in both the upper and lower photomicrographs. Many of these atypical cells are probably present as a result of the patient's splenectomy. Considerable anisocytosis and poikilocytosis with many tear-drop cells, bite cells, fragmented forms, and a few target cells are apparent. Some of the erythrocytes in the upper frame contain Howell-Jolly bodies (DNA fragments) that may be single or multiple, especially in myeloproliferative disorders. These inclusions stain negatively for iron and are eccentrically placed in the red cell cytoplasm. .

Macrocytes have a diameter of 9-14 microns (1 1/2 to 2 times larger than normal red cells) and the MCV is 100 cubic microns or more. The macrocytes seen in this slide are referred to as true macrocytes, or megalocytes. Compare the red cells in the field to the nucleus of the lymphocyte in the lower left. Many of the red cells in the field are larger than the lymphocyte and have little or no central pallor. As a point of reference, the cells just below and above the lymphocyte are macrocytes. Megalocytes are frequently oval and several examples of oval macrocytes can be seen in this field. Megalocytes are the result of decreased deoxyribonucleic acid (DNA) synthesis, frequently due to vitamin B12 and/or folic acid deficiencies. Decreased DNA synthesis causes the nucleus in the developing red cells to mature at a slower than normal rate. Since hemoglobin production is not affected, the mature red cell is larger than normal is filled with hemoglobin.

A normal mature neutrophil is 9-13 microns in diameter and contains 3-5 lobes or segments.When the number of segments is increased to six or more the cell is hypersegmented. Some hypersegmented cells will be larger than in 15 microns. Hypersegmentation is seen most frequently in neutrophils but can also occur in eosinophils and basophils. The nuclear segments are composed of deoxyribonucleic acid (DNA). A defect in the production of DNA causes the maturation process to be slower than normal which in turn causes the nucleus to hypersegment. The cytoplasm will be normal in appearance and function, indicating that these cells are capable of phagocytosis.These cells are considered pathological

There are a number of conditions in which hypersegmented neutrophils may be seen, such as megaloblastic anemias that include folic acid deficiency and pernicious anemia. Individuals who are receiving chemotherapy or have long-term chronic infections may also have hypersegmented neutrophils.The cells seen in these conditions would be classified as pathological since the body is responding abnormally as a result of either a deficiency of a component needed for DNA production or because of the toxic effect that chemotherapy drugs have on DNA.