Biology Test 333

E.coli cloning vector pBR322 contains antibiotic resistance genes for Ampicillin (ampR) and Tetracycline (tetR) as selectable markers.

Selectable markers help in selecting those host cells which contain the transformed vectors and eliminate the non-transformants. Plasmid pBR322 has a variety of unique recognition sites for restriction endonucleases.

Two unique sites—PstI and PvuI—are located within the ampR gene and BamHI and SalI are within the tetR gene.

The key distinguishing feature of eukaryotic cells is the presence of a membrane-bound nucleus, where the cell's genetic material is enclosed. This contrasts with prokaryotic cells, which lack a membrane-bound nucleus, and their DNA is located in a nucleoid region. Eukaryotic cells also contain other membrane-bound organelles, such as mitochondria and the endoplasmic reticulum, further differentiating them from prokaryotic cells.

A restriction enzyme or restriction endonuclease is an enzyme that cleaves DNA into fragments at or near specific recognition sites within molecules known as restriction sites. Restriction enzymes are one class of the broader endonuclease group of enzymes. Each restriction endonuclease functions by inspecting the length of a DNA sequence. Once it finds its specific recognition sequence, it will bind to the DNA and cut each of the two strands of the double helix at specific points in their sugar phosphate backbone. These enzymes predictably cut both strands because the sequences they recognize are palindromic. That is the recognition sequences of identical bases on both DNA strands.

The appendix is an example of a vestigial organ in humans. It is a small, tube-like structure attached to the large intestine, and it is believed to be a remnant of a larger cecum found in our herbivorous ancestors, used for digesting cellulose. In modern humans, the appendix has no significant digestive function, although recent research suggests it may play a role in the immune system. The concept of vestigial organs supports the theory of evolution, indicating that certain structures have lost their original function over time due to changes in species' lifestyles and environments.

Retrovirus is a type of RNA virus that inserts a copy of its genome into the DNA of a host cell that it invades, thus changing the genome of that cell. Retrovirus is commonly used as vector for introducing a DNA fragment in human lymphocyte.

Homo habilis, an early human ancestor, is believed to have had an omnivorous diet. This species, which lived approximately 2.4 to 1.4 million years ago, is thought to have consumed a variety of foods, including plants and meat. Evidence from archaeological sites, including tools and animal bones with cut marks, suggests that Homo habilis used stone tools to butcher animals for meat, in addition to gathering plant materials for food. This dietary flexibility is considered an important adaptation that may have contributed to the survival and evolution of the early human species.

The separated DNA fragments can be seen only after staining them with a compound known as ethidium bromide (EtBr) followed by exposure to UV radiation as bright orange coloured bands.

DNA replication is semi-conservative, meaning that each new DNA molecule consists of one strand from the original molecule and one newly synthesized strand. This was demonstrated by the Meselson-Stahl experiment.

Some genes called "selectable markers" help in selecting those host cells which contain the vectors (transformants) and eliminating the non-trans formants.

RNA indeed acts as the genetic material in some viruses, such as retroviruses. However, RNA is generally less stable than DNA due to the presence of the 2'-OH group in its ribose sugar, making it more prone to hydrolysis.