basal membrane, a sheet of tissue that forms the outer layer of the choroid and lies just under the pigmented layer of the retina. It is composed of elastic fibers in an otherwise thin homogenous layer.asal membrane, a sheet of tissue that forms the outer layer of the choroid and lies just under the pigmented layer of the retina. It is composed of elastic fibers in an otherwise thin homogenous layer.
There are several enzymes that 'unzip' DNA. These enzymes are collectively known as DNA helicases. DNA helicases are helix-destabilizing enzymes that bind to DNA at the origin of replication and break hydrogen bonds, thereby separating the two strands.. Solomon, Eldra P., Linda R. Berg, and Diana W. Martin. Biology. 8th ed. Belmont, CA: Thomson Brooks/Cole, 2008.
At the origin, histones are removed to expose the DNA strand, then the enzyme helicase untwists the replicating portion of the molecule and breaks the hydrogen bonds between complementary base pairs, causing the formation of a replication fork in the direction of replication.