Chapter 1 | Cells, Genomes, and the Diversity of Life

Evolution of living organisms

4.1 BYA

Evolution of Archaea

~2.7 BYA

Eukarya

• Membrane-bound organelles

• Endosymbiotic theory

• Plasma membrane

Multicellularity

• Evolved ~1 BYA

• Not unique to eukaryotes

DNA

• Inherited

• Double helix

• Circular vs linear

• Semiconservative replication / templated polymerization

• Transcription & translation

RNA World Hypothesis

RNA was the first initial storage material before DNA & protein → RNA evolved to make protein → RNA evolved to form DNA

Minimum # of genes

~500 genes require a host organism

~1000 genes are free living

Maximum # of genes

~60,000 so far (amoeba)

Gene duplication events

One gene can undergo a mutation & gene shuffling can occur → gene families

Homologous genes / homologs

Two or more genes that are part of the same gene family

Paralog

Homologs within the same species

Ortholog

Homologs in different species

Horizontal Gene Transfer

Transfer of DNA from one genome to another

Conjugation

Transfer of F plasmid to other species

Transformation

DNA from outside environment

Transduction

Bacteriophages uptake DNA of their host & transfer it to other species

HGT in Eukaryotes

~100 genes have undergone HGT from bacteria to humans

HGT & Disease

Cancerous cells make it easier for bacterial cells to infiltrate & infect the host

HGT through viruses

Viruses encode their genetic code into the host cell

Giant Viruses

• Viruses that can be seen with a light microscope

• Contain well over 500 genes (more than bacteria)

• Meets most criteria of living organisms

Biomolecules & metabolism

All living organisms are capable of metabolizing all major biomolecules

Model organisms

• Convenient

• Easy to grow & maintain

• Ethical

• Small genome

• Simple morphology

• Short reproductive cycles

Model organism for prokaryotes

E. coli

Model organism for simple eukaryotes

Saccharomyces cerevisiae

Model organism for plants

Arabidopsis thaliana

Model organism for simple animals

Caenorhabditis elegans

Model organism for invertebrates

Drosophila melanogaster

Model organism for vertebrates

Danrio rerio (zebrafish)

Model organism for terrestrial vertebrates

Xenopus (frog)

Model organism for mammals

Mus muscula (mice)