Binary fission doesn't shuffle genes
- The idea
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The idea
“When bacteria divide, crossing over and independent assortment mix up their genes.”
Crossing over and independent assortment are the sources of variation you studied most. Both are steps of meiosis, and bacteria never do meiosis.
The short version
The mistake: When bacteria divide, crossing over and independent assortment mix up their genes.
What's actually true: Binary fission copies one chromosome and splits the cell, so nothing gets shuffled. New variation in a clone comes from mutation.
- In binary fission, a bacterium copies its circular chromosome and splits in two. Each daughter gets one copy, so the cells form a clone.
- Crossing over and independent assortment need pairs of homologous chromosomes lined up in meiosis. Fertilization needs gametes. Fission has none of these.
- New alleles in a clone come from mutations, caused by replication errors or by DNA damage from things like UV light.
- Bacteria can also take in DNA from other cells by transformation, transduction or conjugation. That's gene transfer, not meiosis.
On the exam: Asexual division copies DNA without shuffling it. In a clone, new alleles come from mutation.