Exam 2: Topic 8

Question 1

What is a DNA signature?

Answer 1

a nucleotide sequence that can be used to identify the presence of bacteria and distinguish it from other species

Question 2

Contrast the two approaches of using DNA signatures to definitively ID bacteria:
(a) unique gene of a pathogenic bacterium and fluorescent tags
(b) unique sequence of a common gene (such as 16s ribosomal RNA)

Answer 2

○ A) DNA probes with fluorescent tags (best for looking for specific microbe in a large number of samples). Develop a probe for a gene that is unique to the microbe of interest.
○ B) Amplify DNA sequence and determine the actual DNA sequence and reference the sequence with the NIH to determine the microbe under investigation.
For example, the 16 rRNA gene that is the DNA signature for two infectious agents of the lower respiratory tract (Haemophilus influenzae & Mycobacterium tuberculosis).

Question 3

Describe the process by which a recombinant DNA piece is made. Include the
terms vector, plasmid, restriction enzyme, and sticky ends in your explanation.

Answer 3

○ Recombinant DNA piece is made through genetic engineering.
○ A vector is used as a vehicle to carry a specific DNA sequence into a host cell.
○ Restriction enzymes are used to precisely cut DNA at specific nucleotide sequences.
○ Sticky ends are used to allow for precise joining of DNA fragments from different sources.
▪ Ex: Splice in a gene of interest into a plasmid and use transformation to get that plasmid into a bacterial cell, so that the bacteria cell can express that gene of interest.

Question 4

Explain why plasmids used in genetic engineering MUST contain a gene for
antibiotic resistance

Answer 4

○ In order to distinguish which bacteria have transformed and which have not. The bacteria that have transformed survive and grow, while the ones that have not will not survive.