Question

QUESTION 8 1. Are all bacteria competent for transformation?

a. Yes they are all competent b. No, some bacteria in nature can do it and in the lab scientists can force bacteria to be competent. o c. No and nothing can be done about it d. no only yeast are competent 10 points

QUESTION 9 1. Which enzyme "glues" DNA fragments together?

a. DNA Ligase b. DNA Recombinase c. all these enzymes d. DNA Reductase 10 points

QUESTION 10 1. Which of these is an example of xenotransplantaion

a. Using a pig retina to treat eye disease in a man b. Using stem cells to treat cancer c. cloning a pet d. Kidney donation from a father to a son

Answer 1

8.1. B. Not all bacteria are competent for transformation. Some bacteria in nature can do it and in lab scientists can force bacteria to be competent.

Competence is the ability of the bacteria to uptake genes from environment and express them. Some bacteria are naturally competent. For example Streptococcus pneumoniae shows natural competency is in Griffith’s experiment. But some other bacteria like E. coli are not naturally competent and it has to be induced in the laboratory artificially.

9.1 A. DNA Ligase glues DNA fragments together.

DNA ligase is widely used in genetic engineering to ligate breaks between two DNA strands by forming a phosphodiester bond. It is also found during DNA replication where it ligates Okazaki fragments formed in the lagging strand.

DNA recombinase is an enzyme that works in forming recombinant chromosomes during crossing over process in meiosis. During this event the recombinase makes site specific cuts in the chromosome thereby mediating the exchange of alleles between chromosomes. DNA reductase, this enzyme catalyzes the formation of deoxy-ribonucleotides from ribonucleotides. This is very essential in DNA synthesis.

10.1 A. Using pig retina to treat eye disease in man is an example of Xenotransplantation.

Xenotransplantation is the type of transplant occurring between different species, here a transplant from a non-human source to a human source.

Using stem cells to treat cancer is a form of stem cell therapy. It is also transplanted in people who have lost some functional cells in cancer treatment. Kidney donation from a father to a son is an example of allograft.