Ch. 15 - Recombinant DNA Technology and Its Applications

Sanders - Genetic Analysis: An Integrated Approach 3rd Edition

Sanders3rd EditionGenetic Analysis: An Integrated ApproachISBN: 9780135564172당신이 사용하는 게 아니라요?교과서 변경

Sanders 3rd Edition

Ch. 15 - Recombinant DNA Technology and Its Applications

문제 6

15장, 문제 6

The human genome is 3×10⁹ bp. You wish to design a primer to amplify a specific gene in the genome. In general, what length of oligonucleotide would be sufficient to amplify a single unique sequence? To simplify your calculation, assume that all bases occur with an equal frequency.

검증된 단계별 안내

Understand that the goal is to find the length of an oligonucleotide (primer) that will uniquely bind to one specific sequence in the human genome, which is 3 × 10⁹ base pairs (bp) long.

Assume that each base (A, T, C, G) occurs with equal frequency, so the probability of any specific base at a position is 1/4.

Calculate the total number of possible sequences of length

n

4^n

, since each position can be one of four bases.

To ensure uniqueness, the number of possible sequences of length

n

should be at least equal to the size of the genome, so set up the inequality:

4^n  3 	imes 10^9

Solve for

n

by taking the logarithm base 4 of both sides:

n  rac{\(\u\)221A \(\text{log}\)(3 	imes 10^9)}{ \(\text{log}\)(4)}

. This will give the minimum primer length needed to uniquely amplify a single sequence.

비슷한 문제에 대한 검증된 영상 답변:

이 영상 해법은 위 문제에 도움이 된다고 튜터들이 추천한 것입니다.

영상 길이:

주요 개념

질문에 올바르게 답하기 위해 반드시 이해해야 하는 핵심 개념들은 다음과 같습니다.

Primer Specificity and Length

Primer specificity depends on its length and sequence uniqueness. Longer primers are more likely to bind uniquely to a target sequence in a large genome, reducing non-specific binding. Typically, primers between 18-25 nucleotides provide a good balance of specificity and efficient binding.

Probability of Sequence Occurrence

The probability of a specific oligonucleotide sequence occurring in a genome depends on its length and base composition. Assuming equal base frequency, the chance of any particular sequence of length n is (1/4)^n. This helps estimate how long a primer must be to appear uniquely in a genome of given size.

Human Genome Size and Complexity

The human genome contains approximately 3×10⁹ base pairs, which influences primer design. To ensure a primer binds uniquely, its length must be sufficient so that the expected number of occurrences of that sequence in the genome is close to one or less, considering the genome's size and base distribution.

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