Transposable elements

Transportable elements are DNA Sequences that move from one location in a chromosome to another within the same chromosome or into another chromosome.
These are DNA Sequences that move from one location in a chromosome to another within the same chromosome or into another chromosome.
These are DNA Sequences that move from one location in a chromosome to another within the same chromosome or into another chromosome.
These are also known as “Jumping genes”.

1. DEPARTMENT OF GENETICS AND PLANT BREEDING NAINI AGRICULTURAL INSTITUTE SAM HIGGINBOTTOM UNIVERSITY OF AGRICULTURE TECHNOLOGY AND SCIENCES PRAYAGRAJ-211007 Transposable elements Student: Munagala Sai kiran 18MSCGPB090 M.Sc.Ag .(Genetics and Plant breeding)

2. Transposable elements

3. Definition's These are DNA Sequences that move from one location in a chromosome to another within the same chromosome or into another chromosome. A Transposable element is a DNA Sequence that can change its position within a genome. These are also known as “ Jumping genes”. Transposition results in duplication of the genetic material. Transposable elements(both active and inactive) occupy approximately half the human genome and a substantially greater fraction of some plant genomes!

4. Transposable elements (TE) are 1 st discovered by Barbara McClintok in corn(maize) in 1940. She was awarded a Nobel prize in Physiology/Medicine in 1983 for her discovery of Transposable elements(TE) more than 30 years after her initial research. she found genetic elements regularly jump to new location affecting the gene expression . Maize kernels show variation in colour. Barbara McClintok Barbara McClintok (American scientist) Born:16 th June 1902, Harfford USA Died: 2 september 1992, NYC, USA  

5. Comprises 45% of the human genome. She noticed chromosomal insertion,deletion,translocation caused by these TE. Later in 1960’s Bacteria & Bacteriophages were shown to possess Transposable elements(TE ). Campbell in 1977 described the nomenclature in prokaryotes initially named Insertion sequences(IS ). The Transposable elements (TE) were found to be DNA sequences that code for enzymes, which bring about the insertion of an identical copy of themselves into a new DNA site. Transposition events invovlve both recombination and replication processes which frequently generate two daughter copies of the original transposable elements. One copy remains at the parent site & another appears at the target site

6. A transposable element (TE) is not a replicon so, it can’t replicate apart from the host Chromosome. It is a DNA sequence that can change its position within a genome. Sometimes creating or reversing mutation and altering the cell’s genetic identity & genome size. One group of transposable elements propagates itself by transposition as DNA copies e.g., Insertion sequences (IS) and composite transposons Another group of transposable elements propagates itself by making DNA copies of their RNA genomes. The DNA copy is transcribed to yield the RNA genomes e.g. Retroposons .

7. Types of transposable elements: Different types of transposable elements are present in both Prokaryotes and Eukaryotes 1. Insertion sequences. 2.Transposons. 3. Bacteriophage µ

8. Insertion sequences These are the first transposable element discovered in prokaryotes(bacteria) IS were the first transposable elements identified as spontaneous insertion in some bacterial operon Initially these are names as insertion sequences- IS, IS 1 , IS 2 ,IS 3 , etc…. These IS are short DNA sequences of about 800-1400 base pairs and do not code for proteins

9. They also promote recombination between non-homologous chromosome such recombination is illegitimate recombination The first four base pairs discovered in E coli were designated as IS 1 , IS 2 , IS 3 , IS 4 Is elements have usually 9-24 bp inverse repeats

10. Transposons Transposons are similar to IS elements but carry additional genes Transposons are several thousands base pairs long and have genes coding for one or more proteins On either side of a transposon is a short direct repeat. the sequence into which the transposable element insert is called target sequence There are two types of transposon 1.Composite transposon 2.Non Composite transposon

11. Composite transposon : Any segment of DNA that flanked by two copies of an IS and central coding region with antibiotic resistant gene and no marker gene

12. Non composite transposon : Do not terminate with IS elements but contain terminal inverted repeats

13. Bacteriophage µ; The longest transposon knows so far Caries numerous genes for viral head and tail formation The vegetative replication of Mu produces about 100 viral chromosomes in a cell arises from the transposition of Mu to about 100 different target sites There fore considered as giant mutator transposon

14. Barbara McClintock Receiving Nobel prize 1983