One of the main differences between the mouse and human genomes lies in the activity of junk' DNA sequences called retrotransposons. Carina Dennis considers what these sequences might be doing.
In the paragraph below, you must find the words that belong to the same family as the words in brackets.They could be verbs, adverbs, adjectives, etc.. ( i.e. " understand " gives the adjective "understandable"). Once you've found the words type them in the space provided for each numbered gap below the text.
Wherever human garbage accumulates, mice will forage. But in (1)……………….. (gene), the tables are being turned. For some (2) ……………….. (gene), the most intriguing aspect of the mouse genome lies in its 'junk' - DNA sequences that don't code for proteins. The mouse, they believe, will prove a fertile (3) ……………….. (hunt) ground for researchers who want to understand why and how mammalian genomes accumulated this garbage, and whether it has any function.
Much of the junk is the work of transposons, genetic 'parasites' that have accumulated in mammalian genomes over millions of years by being copied into new (4) ……………….. (gene)locations. Most are retrotransposons, which reproduce through an RNA intermediate, and so must use a reverse transcriptase enzyme to (5) ……………….. (restoration) their original DNA sequence as they jump back into the genome.
The mouse genome is not especially full of such garbage - although at least 37.5% of it seems to be derived from retrotransposons, the proportion is similar in the human genome. But the activity of these retrotransposons (6) ……………….. (difference) greatly. In our evolutionary (7) ……………….. (line), retrotransposon activity seems to have (8) ……………….. (quiet) down about 40 million years ago, and less than 100 are (9) ……………….. (activity) jumping around in any individual's genome today. But in the mouse, about 3,000 of these parasites are thought to be still on the move, occasionally (10) ……………….. (disruption) host genes and affecting the creature's genome in ways that scientists are keen to investigate. "I believe that some of these elements have been the most dynamic forces to sculpt the genome," says Sandra Martin, who works on retrotransposons at the University of Colorado Health Sciences Center in Denver.
Gap n°1 (gene)
Gap n°2 (gene)
Gap n°3 (hunt)
Gap n°4 (gene)
Gap n°5 (restoration)
Gap n°6 (difference)
Gap n°7 (line)
Gap n°8 (quiet)
Gap n°9 (activity)
Gap n°10 (disruption)
Click here for more on the Mouse Genome.