​

The statements below attempt to describe a few characteristics of Alu repeats found in the human genome:

A. Alu elements are a class of short interspersed elements (SINEs).
B. SINEs are autonomous transposons.
C. Alu repeat originated from cDNA copies of 7SL RNA.
D. Alu repeats have a relatively high AT content.
E. They are preferentially located in the gene-poor G chromosome bands.

Which one of the following options shows the combination of all correct statements?

Correct option is C

​

1.      Statement A - Correct:

o   Alu elements are classified as short interspersed elements (SINEs).

o   SINEs are a class of retrotransposons that do not encode their own reverse transcriptase but rely on other mobile elements (e.g., LINEs) for transposition.

2.      Statement B - Incorrect:

o   SINEs are not autonomous transposons because they lack the necessary enzymatic machinery for their own mobilization.

o   Unlike LINEs, which encode reverse transcriptase, SINEs require the LINE-1 (L1) retrotransposon machinery for transposition.

3.      Statement C - Correct:

o   Alu repeats originated from cDNA copies of 7SL RNA, a component of the signal recognition particle (SRP).

o   Alu elements are derived from processed RNA sequences and subsequently amplified in the genome.

4.      Statement D - Incorrect:

o   Alu elements are GC-rich, not AT-rich.

o   They are predominantly found in gene-rich, GC-rich regions of the genome.

5.      Statement E - Incorrect:

o   Alu elements preferentially localize in GC-rich regions, which are typically gene-rich regions.

o   G-bands on chromosomes are gene-poor and AT-rich, where Alu elements are less frequent.

Thus, the correct statements are A and C only, making option (3) the correct answer.

Information Booster:

1. Alu elements are the most abundant transposable elements in the human genome, making up about 10% of total DNA.
2. They are non-autonomous transposons, meaning they require LINE-1 elements for mobilization.
3. Alu sequences originated from 7SL RNA, a component of the signal recognition particle (SRP), which plays a role in protein targeting.
4. They are preferentially found in GC-rich regions, often near genes and regulatory elements.
5. Alu elements are linked to genome evolution, genetic disorders, and some diseases such as Alu-mediated recombination disorders.