Question 1: Cockayne syndrome is a rare disorder in humans characterized by an abnormally small head size (microcephaly), failure to gain weight, very short stature, and delayed development. Most affected individuals have an increased sensitivity to sunlight (photosensitivity), and in some cases even a small amount of sun exposure can cause a sunburn or blistering of the skin. Mutations in the ERCC6 (CSB) gene are one of the causes of Cockayne syndrome.
- What is the normal function of the ERCC6 protein in the body? Need Assignment Help?
- How can a mutation in this gene explain the photosensitivity phenotype observed in affected individuals?
Question 2: DNA replication in both prokaryotic and eukaryotic cells involves dozens of different proteins/factors acting in concert to synthesize new DNA molecules. However, when a Polymerase Chain Reaction (PCR) is set up in the lab, only one protein, DNA Polymerase, is needed. How is it possible to replicate (copy) DNA in vitro, using PCR, with a single enzyme, i.e., why are these other proteins/factors not needed?
Question 3: Crown gall disease in plants is caused by the soil bacterium Agrobacterium tumefaciens. These bacteria are considered natural "genetic engineers" of plants given their mechanism of infection of plant cells.
- What are the bacterial genes involved in the infection process, their functions (if known), and how are they activated?
- How is it possible that the tumors that are characteristic of the disease can persist even when the bacteria are no longer found in the plant?
- These bacteria have been engineered to transform desired genes into plants to create transgenic plants. This transformation method uses a binary plasmid system. Describe how this binary system works and its components.
Question 4: DNA synthesis is normally a very accurate process in living cells, as mutations introduced during DNA replication may have serious consequences to the organism. However, error-prone DNA synthesis may occur in E. coli under certain conditions, for example when there has been widespread DNA damage, such as that following UV irradiation. Scientists may actually induce inaccurate DNA replication in vitro in a molecular biology technique called error-prone PCR. Explain how this technique works, and what might be the purpose of using error-prone PCR to investigate the function of genes?