Question

DNA element with the ability to change position is called as
(a) Cistron
(b) Transposon
(c) Intron
(d) Recon

Answer 1

Hint: DNA element with the ability to change position is one of the reasons behind genetic rearrangements in the chromosomes and thus the evolution of new traits or characters. They were discovered by Barabara McClintock for which she was awarded the Nobel Prize.

Complete answer:
Transposons are found in both prokaryotic and eukaryotic genomes. They were first discovered in maize in 1948 by Barabara McClintock. She was awarded the Nobel prize for this discovery in 1983. They are commonly known as jumping genes. These are genomic sequences that can change their position and jump to different locations within a genome. They can do so whether by the conservative or replicative process.

Additional Information: -In the replicative process, they create a copy of themselves by replication. The second copy is inserted at a new position while the original one remains in its position. Transposons using this mechanism are known as complex transposons as it increases the genomic content on the whole.
-In conservative transposition, there is an excision of the sequence from its original position followed by its reinsertion elsewhere. It involves a change in the position of a transposon in the genome without increasing its copy number.
-Cistron is a primitive name for a gene. It is a segment of nucleotide sequences on DNA containing all the necessary information for the production of a polypeptide. This term was coined by Seymour Benzer.
-Introns are non-coding nucleotide sequences within a DNA that is represented in the primary transcript of the gene, but not present in the final processed form. They are removed via a process known as splicing aided by a multi-unit complex of the spliceosome.
-Recon is a term coined by Seymour Benzer which are the smallest units of recombination i.e these are the locations within a gene capable of recombination. Two or more recons combine to produce a new genetic combination.
So, the correct answer is ‘Transposons.’

Note: -In eukaryotes, transcription produces a primary transcript hnRNA which contains both the coding and non-coding sequences. They are known as exons and introns respectively.
-hnRNA or heterogeneous RNA undergoes processing involving splicing, tailing, and capping. The fully processed hnRNA is now known as mRNA or messenger RNA.