Prokaryotes

Bacteria cells

Small, no nucleus membrane, no organelles, unicellular, 1 circular chromosome and simple

Eukaryotes

Large, nucleus, organelles, uni/multicellular, many linear chromosomes and complex

Bacteria description

Bacteria have a large central vacuole which limits the volume of the effective cytoplasm. So, the effective surface to volume ratio is less disadvantageous than what would be predicted by its size

Bacteria characteristics

Small, rapid reproduction, mutations produce high genetic diversity (rapid evolution), diverse adaptions

Bacteria reproduction

One circular chromosome, DNA duplicated, cytoplasm pinched off, 2 identical daughter cells

Evolution - mutations

A low mutation rate combined with short generation times make a big impact on mutations

Transformation

Bacteria have surface proteins that recognise naked DNA from the same species or closely related species available in the surrounding environment and internalise it. This exogenous DNA is incorporated into the genome by homologous recombination

Transduction

Bacteriophages carry DNA from one bacterium to another. Often they incorporate foreign DNA by accident and lose the ability to replicate but transfer the foreign DNA to the new bacterium

Conjugation and recombination

2 cells exchanging DNA come into physical contact through a pilum. Donor cell has fertility factor, recipient does not. Conjugation can be considered a form of mating for asexually reproducing bacteria, no offspring generated

A pilum

connects the 2 cells and DNA passes inside the pilum while being replicated

Horizontal Gene Transfer

Movement of DNA in the same generation. Transformation, transduction and conjugation can be defined as forms of this, which occurs between bacteria of the same species. When DNA moves between distantly related species, or even between different domains of life, the definition of HGT applies

Mechanisms of HGT

Exchange of transposable elements, viral infection and fusion of an organism with its endosymbiont