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1) What structural motif is most commonly used by transcription factors in bindi

ID: 50172 • Letter: 1

Question

1) What structural motif is most commonly used by transcription factors in binding to DNA?

a) Zinc- finger

b) Helix-turn-helix

c) Homeodomain

2) Kozak’s rules for translation are similar to those for transcription in prokaryotes in that they both contain consensus sequences. In prokaryotes, the promoter consensus sequences are at -35 and -10. Where is the consensus sequence for translational initiation according to Kozak’s rules?

a) -6 to + 10

b) -12 to -2

c) +1 and +10

3) A culture of E.coli bacteria is used to establish several subcultures. Each subculture is then plated and individual colonies that grow on the agar plates are then tested for their sensitivity to the bacteriophage T1. There is a spectrum of sensitivities where some plates have a high number of resistant colonies and some plates had very few. This data supports which theory?

a) Physiological adaptation theory

b) Random mutation theory

c) Neither theory

Explanation / Answer

1. Option b) The Helix-turn-helix motif, is the most commonly used structural motif.

2. The nucleotides at positions +4 and -3 with respect to number 1 nucleotide of of AUG (initiation codon) is the consensus sequence of the Kozak's rule

3. Random mutation theory; the theory says that mutants always exist in the population and it is not directed by any mutagenic agent in a specified condition.