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Short tandem repeats (STRs) are short sequences of DNA, usually 2 to 7 base pairs - AQA - A-Level Biology - Question 9 - 2023 - Paper 2
Question 9
Short tandem repeats (STRs) are short sequences of DNA, usually 2 to 7 base pairs. STRs are repeated a number of times, one after another. For example, the STR D5581... show full transcript
Worked Solution & Example Answer:Short tandem repeats (STRs) are short sequences of DNA, usually 2 to 7 base pairs - AQA - A-Level Biology - Question 9 - 2023 - Paper 2
Step 1
Describe how STRs could be removed from a sample of DNA.
Answer
STRs can be removed from a sample of DNA using restriction endonucleases or enzymes that cut DNA at specific base sequences or pairs. By targeting specific recognition or restriction sites, the enzymes can effectively cleave the DNA, allowing for the isolation or removal of STR sequences.
Step 2
Explain the importance of knowing these base sequences in PCR.
Answer
Knowing the base sequences surrounding the STRs is crucial in PCR for several reasons. Firstly, these sequences act as primers which are essential for initiating the DNA synthesis process. Secondly, they ensure that the Taq polymerase can effectively amplify the target STR, providing a complementary sequence for the DNA replication process. Moreover, having accurate sequences helps in reducing non-specific binding, thereby increasing the efficiency and specificity of the PCR amplification.