A cross is made between Hfr met+ thi+ pur+ X F- met- thi- pur-.
Interrupted-mating studies show that met+ enters the recipient last, so met+ exconjugants are selected on medium containing thi and pur only. These exconjugants are tested for the presence of thi+ and pur+. The following numbers of individuals are found with each genotype:
met+ thi+ pur+ 280
met+ thi+ pur- 0
met+ thi- pur+ 6
met+ thi- pur- 52
Mechanisms of Genetic Recombination in Nature
1. Transformation, conjugation, and transduction were discovered in the laboratory. How important are these mechanisms of genetic recombination in nature?
2. What is the process of DNA fingerprinting, and how is electrophoresis used in criminal forensics?
3. How can plasmids be used to manufacture proteins such as insulin for diabetic patients, or antibiotics for bacterial infections?
4. Research a genetic disease that may be cured through the use of genetic engineering. What techniques are being explored to correct the problem? How do concerns of designer embryos stem from this technology?
5. How can DNA be fragmented into very specific sections?
6. Where do restriction enzymes come from? What is their function in nature?
7. How do molecules of varying sizes separate in electrophoresis? What is the purpose of the gel? What about the electricity?
8. Investigate one way in which electrophoresis is used in medicine today.
9. Why is electrical current necessary to separate molecules using electrophoresis?
10. Why is agarose an appropriate medium to use for separating molecules? Research another type of gel and provide a brief explanation regarding why it could be used rather than an agarose gel.
11. How is electrophoresis similar to, and different from chromatography?