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The restriction endonuclease EcoRI cuts the palindromic sequence GAATTC. What are the odds that it will cut a random stretch of 6 nucleotides?

approximately 1 in 4,000
approximately 1 in 10
approximately 1 in 1,300
approximately 1 in 262,000
approximately 1 in 25

1 Answer

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The sequence GAATTC is a palindromic sequence, meaning it reads the same forward and backward. Therefore, the odds of EcoRI cutting a random stretch of 6 nucleotides is the same as the probability of randomly selecting the sequence GAATTC within a 6-nucleotide stretch.

Each nucleotide in DNA can be one of four possibilities: A (adenine), T (thymine), G (guanine), or C (cytosine). Therefore, the probability of randomly selecting GAATTC within a 6-nucleotide stretch is (1/4) * (1/4) * (1/4) * (1/4) * (1/4) * (1/4) = (1/4)^6.

Simplifying this expression, we have (1/4)^6 = 1/4096.

Therefore, the odds that EcoRI will cut a random stretch of 6 nucleotides is approximately 1 in 4,096.

Therefore, the closest option is "approximately 1 in 4,000".

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