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Genetics 301 Quiz #9
Spring 2003
Class week 12

 

  1. (3 pts.) On average, how many fragments would a restriction enzyme which recognizes a specific 6 base sequence in DNA be expected to cleave the bacteriophage lambda (50 kb) into?

6 base cutters would be expected to cut about every 4096 bp (= 46).

Thus, lambda should be cleaved into about 12 pieces.
  1. (3 pts.) Does the sequence below represent an "open reading frame" for any of the three reading frames? You can read this DNA sequence as an mRNA by substituting U for T. (The three stop codons are UAA, UAG and UGA).

AGA/GAC/TAA/GGG/CTA/GCC/CGT/GAC/CGG/CGT/GG

There is a stop condon in each of the three reading frames, as indicated above.

 
  1. (4 pts) For the lac operon system, match the mutation with the corresponding phenotype. Each mutation matches with one phenotype and none of the phenotypes are used more than once.

Mutation

i- repressor can’t bind operator 3

oc operator can’t bind repressor 2

P- Promoter can’t b ind RNA polymerase 1

is Repressor can’t bind lactose 4

Phenotypes
  1. lac Z not produced under any circumstances on chromosome carrying this mutation
  2. lac Z always produced on chromosome bearing this mutation
  3. lac Z always produced in individuals with only this mutation, but mutation is recessive
  4. Dominant mutation which prevents lacZ production