Question

The human genome contains approximately \(10^{6}\) copies of an \(A l u\) sequence, one of the best-studied classes of short interspersed elements (SINEs), per haploid genome. Individual Alus share a 282-nucleotide consensus sequence followed by a 3'-adeninerich tail region (Schmid, 1998. Nucl. Acids Res. 26: 4541-4550). Given that there are approximately \(3 \times 10^{9}\) bp per human haploid genome, about how many base pairs are spaced between each Alu sequence?

Short answer

Answer: The average distance between Alu sequences is \((3\times10^9 - 10^6 \times 282) / 10^6\) base pairs.

Step-by-step solution

Calculate the Total Number of Base Pairs in Alu Sequences

First, we need to find out how many base pairs in total are contained in the Alu sequences in the human genome. We are given that each Alu sequence has 282 base pairs, and there are \(10^6\) Alu sequences per haploid human genome. So, we can multiply the number of Alu sequences by the base pairs in each Alu sequence: Total base pairs in Alu sequences = Number of Alu sequences × Base pairs in each Alu sequence Total base pairs in Alu sequences = \(10^6 \times 282\)

Calculate the Total Number of Base Pairs Not in Alu Sequences

Now we can find the total number of base pairs in the human genome that are not part of Alu sequences. We know there are \(3\times10^9\) base pairs in total per haploid human genome. We'll subtract the total base pairs in Alu sequences (calculated in Step 1) from the total base pairs in the human genome. Total base pairs not in Alu sequences = Total base pairs in the human genome - Total base pairs in Alu sequences Total base pairs not in Alu sequences = \(3\times10^9 - 10^6 \times 282\)

Calculate the Average Distance Between Alu Sequences

Now that we have the number of base pairs that are not part of Alu sequences, we can divide this number by the number of Alu sequences (\(10^6\)) to find the average distance between two Alu sequences in base pairs. Average distance between Alu sequences = Total base pairs not in Alu sequences / Number of Alu sequences Average distance between Alu sequences = \((3\times10^9 - 10^6 \times 282) / 10^6\) Now, we can calculate the average distance between Alu sequences: Average distance between Alu sequences = \((3\times10^9 - 10^6 \times 282) / 10^6\)