Back to: MICROBIOLOGY 200 LEVEL
Welcome to class!
Hello again, brilliant scholar! It’s always exciting to learn with someone as curious and determined as you. Today’s topic is one that truly shows how fascinating and flexible DNA can be — we’re going to look at Insertion Sequences and Transposons. These are like little travellers or “jumping genes” that can move around within a genome. Don’t worry, we’ll break it down into simple ideas with relatable examples, just like always.
Insertion Sequences And Transposons
Have you ever rearranged furniture in your room — moving your reading table from one corner to another to create more space or get better light? That’s how insertion sequences and transposons behave in the genome. They are special segments of DNA that can move from one place to another, sometimes carrying other genes with them. This movement can change how genes work, and it can even introduce new traits to bacteria.
Let’s understand each one.
Insertion Sequences (IS elements)
These are the simplest type of mobile genetic elements.
They carry only the gene that helps them move, usually called the transposase gene.
They don’t carry any extra genes like antibiotic resistance or toxin genes.
How they work:
The transposase enzyme recognises specific sequences at the ends of the insertion sequence.
It cuts the DNA and helps the IS element “jump” into a new position in the genome.
Why they matter:
They can disrupt genes when they insert into the middle of them — just like how a roadblock can disrupt traffic.
This can cause mutations, change gene expression, or even turn a gene off.
Transposons
Transposons are larger and more complex than insertion sequences.
They carry not just the genes for movement, but also extra genes, such as those for:
Antibiotic resistance
Virulence factors (which make bacteria more harmful)
Enzymes for breaking down new substances
Types of Transposons:
Simple transposons (composite transposons): Made of two IS elements with other genes sandwiched in between.
Complex transposons: Have their own transposition machinery and may carry several genes.
How they move:
Like insertion sequences, they move using transposase.
Some move by cut-and-paste, while others make a copy of themselves and move the copy to a new location.
Why they matter:
They contribute to genetic variation.
They help bacteria adapt to stress, such as antibiotics.
In medicine, they can spread resistance quickly from one bacterium to another.
Summary
- Insertion sequences are simple mobile DNA elements that carry only the transposase gene.
- Transposons are larger and can carry other useful or harmful genes.
- Both elements move around the genome and can cause mutations.
- Transposons can help bacteria gain antibiotic resistance or other survival traits.
- These mobile elements contribute to evolution and adaptation in microorganisms.
Evaluation
- What is the main difference between an insertion sequence and a transposon?
- What is the role of transposase in gene movement?
- Mention one benefit and one risk of transposons in bacteria.
- How can insertion sequences affect gene function?
- Why are transposons important in the spread of antibiotic resistance?
Great work today! You’ve just learnt how genes can move around like passengers on a danfo bus — sometimes causing trouble, sometimes saving the day. Keep going strong. Every topic you master brings you closer to becoming a confident microbiologist. Afrilearn is proud to be your learning partner, and your next class is just around the corner. Let’s go!