Edexcel A Level Biology Student Book 2, Book 2 answersWatch
the questions were;
6. Which one of the following base sequences is most likely to be a recognition sequence of a restriction endonuclease?
7. A transgenic bacterium has
a) Gained one or more genes from another organism
b) Lost one or more genes to another organism
c) Undergone hormonal gene transfer via conjugation
d) Many plasmids (1)
8. A scientist used the polymerase chain reaction (PCR) in amplifying DNA. She set up four tubes containing the essential ingredients for the PCR to occur. In addition she added to each tube DNA nucleotides in which the pentose sugar was dideoxyribose, Nucleotides containing this pentose sugar behave in the same way as those in the pentose sugar is deoxyribose, with one important exception. As soon as a nucleotide containing dideoxyribose is inserted into a developing DNA stand, it terminates further replication.
One of her tubes contained dideoxynucleotides carrying the base Adenine (ddNA); the second contained didenucleotides carrying the base cytosine (ddNC): the third contained didenucleotides carrying the base guanine (ddNG): the fourth contained didenucleotides carrying the base thymine (ddNT). She then placed samples from each tube into separate wells in an agarose gel and carried out electrophoresis. This diagram shows her results:
a) Which electrode would she have connected to the gel at the top of the diagram? (1)
b) Explain why the fragments of DNA produced the bands you can see in the diagram (3)
c) From the information in the diagram, this scientist was able to deduce the base sequence of the template DNA replicated by the PCR. Explain how she was able to do this and give the base sequence of the template DNA strand