The human genome contains approximately 10⁶ copies of an Alu sequence, one of the best-studied classes of short interspersed elements (SINEs), per haploid genome. Individual Alu units share a 282-nucleotide consensus sequence followed by a 3'-adenine-rich tail region [Schmid (1998)]. Given that there are approximately 3 x 10⁹ base pairs per human haploid genome, about how many base pairs are spaced between each Alu sequence?

Key Concepts

Alu Sequences

Alu sequences are a type of short interspersed nuclear element (SINE) found in the human genome. They are approximately 300 base pairs long and are derived from the 7SL RNA gene. Alu elements are notable for their high copy number, with around 1 million copies present in a single haploid human genome, contributing to genomic diversity and evolution.

Haploid Genome

A haploid genome contains a single set of chromosomes, which in humans consists of about 3 billion base pairs. This is half the number of chromosomes found in diploid cells, which contain two sets. Understanding haploidy is crucial for calculating the distribution of genetic elements, such as Alu sequences, across the genome.

Base Pair Spacing

Base pair spacing refers to the average number of base pairs that separate repetitive elements like Alu sequences within the genome. To calculate this, one can divide the total number of base pairs in the haploid genome by the number of Alu copies. This metric helps in understanding the density and distribution of these genetic elements throughout the genome.