12/ bacterial genes 2

Question 1

info on e coli chromosome

Answer 1

• circular
• 4288 genes
• transcription can be clockwise or anti
• replication in both directions

Question 2

why did bacteria develop restriction enzymes

Answer 2

defense against viruses

Question 3

are plasmids dependent on host chromosomes for replication

Answer 3

no

Question 4

info on pBR322

Answer 4

• widely used in molecular cloning
• has an origin of replication
• 2 antibiotic resistance genes
• 3 unique 6 bp restriction sites (PstI, HindIII, BamHI) italics

Question 5

features of resistance plasmid R100

Answer 5

• resistance genes to toxic chemicals
• insertion sequences
• transfer functions
• encodes replication proteins
• natural plasmid, huge

Question 6

how can you isolate bacteria w resistance genes

Answer 6

• grow on antibiotic
• white dots w bacteria have mutated spontaneously and grow on antibiotic

Question 7

nomenclature rules in bacterial genetics - gene, wt, mutant, multiple alleles, phenotype

Answer 7

• gene 3 or 4 letters in italics. lowercase except 4th letter
• wt gene has a superscript plus
• mutant gene has NO superscript -
• several alleles? number genes 1, 2 etc
• phenotype: same as gene but plus or minus to show presence of property, not in italics
• protein: same as gene but 1st letter capital and not in italics

Question 8

kind of mutant - auxotroph

Answer 8

loss of enzyme in a biosynthetic pathway

Question 9

list of chemical and physical mutagens and their mode of action

Answer 9

• base analogs - 5-B/2-A. incorporated like T/A w occasional faulty pairing w G/C
• chemicals reacting w dna
• intercalating dyes - acridines, ethidium bromide (fluorescent). inserts between 2 base pairs
• radiation -uv, x rays. pyrimidine dimer formation, free radical attack on dna, breaking chain