Cycle 6: Endosymbiosis and Antibiotics Flashcards
Three domains of life….appreciate all the differences know 3 of them. Role of rRNA gene sequencing
Three domains of life:
- Bacteria
- Archaea
- Eukarya
These are identified by rRNA sequencing for molecular evidence (e.g. sequence information).
While bacteria and archaea are simple life forms, they can be chemically complex.
What was LUCA….common characteristics that are found across all domains.
LUCA is the last universal common ancestor between the three domains of life and while there’s no physical evidence for existence, but they share DNA, RNA, proteins, etc.
Could have been many “origins of Life” not all led to LUCA.
Basics of evolution of life…anaerobic….to aerobic…
Earliest life forms were anaerobic. Then, cyanobacteria evolved oxygenic photosynthesis during the Great Oxygenation Event (GOE) - they are the first life froms to use oxygen as proton donors for photosystem II. Subsequently, there was a rise in the prevalence of aerobic bacteria, which consume oxygen and perform OxPhos.
Idea behind why eukaryotes are more complex: role of O2 and mitochondria
Aerobic bacteria tend to be simple, because unlike eukaryotic cells, which are much bigger and so have MANY mitochondria, they are unable to generate the large amounts of ATP required for complexity. Oxygen is required for complexity! (higher ATP yield)
Link between Great Oxygenation Event and increase in organism complexity (cell types, genes, genome size).
During the GOE, there was a significant rise in eukaryotic complexity in terms of three main metrics:
1) # cell types
2) # genes
3) genome size
see figure on slides?
Why don’t prokaryotes have bigger genomes…more complex?
Prokaryotes don’t have bigger genomes and aren’t more complex because there’s an energetic cost associated with maintaining a giant genome. elaborate
Origin of endomembrane system, nuclear membrane.
An anaerobic ancestral prokaryotic cell is the origin of an infolding of the plasma membrane and the formation of the nucleus and ER (also nuclear membrane).
What is endosymbiosis and what the 6 lines of evidence (Section 1.6b)
Endosymbiosis is where one organism (e.g. mitochondria and chloroplasts) lives within another (i.e. eukaryotic cells).
Six lines of evidence for endosymbiosis:
1. Morphology
2. Reproduction
3. Genetic Info
4. Transcription and Translation
5. Electron Transport (has its own electron transport chain, since it was once free living)
6. Sequence Analysis
elaborate!!!!!!!!
Relative sizes of typical mitochondrial, chloroplast (compared to bacterial ancestor)
Why have the genomes shrunk compared to ancestors (redundancy and horizontal gene transfer).
There’s a huge reduction in genome size from prokaryotic ancestors to its current form as organelles. This is because the many tasks required for a free-living cell are redundant/obsolete since the cell that engulfed it already has those genes (e.g. protein transportation). Otherwise, many genes moved to the nucleus via horizontal gene transfer (HGT), with no change to gene function.
What is horizontal gene transfer (HGT) and why do we think it occurs between mitos/chloros and the nucleus.
Horizontal gene transfer refers to the relocation of genes from one genome to another.
Detecting horizontal gene transfer using DNA hybridization…Can you interpret the pattern of the result?
Role of the signal peptide in trafficking nuclear-encoded proteins that end up in the mitochondria or chloroplasts.
Basics of protein targeting to organelles via a signal peptide.
