Smith for Midterm Flashcards
Which domain represents the most ubiquitous form of life?
archaea
If one organism is eaten by another, not digested and loses a gene allowing it to be free-living, what is this called?
endosymbiotic gene loss
What is endosymbiotic gene transfer?
endosymbiont genes are transferred to the host
host gains more control, endosymbiont loses autonomy
What was eukaryotic life the result of?
an endosymbiotic event between bacteria and archaea 1.8bya
resulted in mitochondria
What is believed to be the endosymbiont that was the start of eukaryotic life?
alpha-proteobacterium
How much of the nuclear genome of eukaryotic cells came from the endosymbiont? What is this called? Is this still going on?
35-75%, called the “endosymbiotic footprint”
still ongoing
What was involved in the genetic merger that gave rise to chloroplasts?
cyanobacteria and a eukaryotic host
List the 6 steps for a genetic merger
1) Feeding (engulfs it)
2) Endosymbiosis (stays, isn’t digested)
3) Sharing (i.e. benefit)
4) Entrapment (gene loss)
5) Transfer of control (gene transfer)
6) Genetic integration
What are genetic mosaics? What are 2 examples?
the result of genetic mergers between 3 things
plants and algae are examples
Who is Lynn Margulis?
the endosymbiosis to make mitochondria and chloroplasts was her idea
When did the endosymbiosis event occur between a cyanobacterium and a eukaryotic host?
1.5 bya
Give examples of eukaryotic organisms with 2 genomes. What genomes are they?
nuclear and mitochondrial
humans, jellyfish, dogs, mushrooms etc
How many genomes do RBCs have?
only have one (mitochondrial) because they don’t have a nucleus
Give examples of eukaryotic organisms that have 3 genomes. What genomes are they?
nuclear, mitochondrial and chloroplast
i.e. plants and algae
What is an example of a eukaryote with only one genome? Describe it
Microsporidian parasites
intracellular parasites that infect fish, humans, rodents etc
they are closely related to mushrooms and yeast, are actually fungi
They have lost their mitochondrial genome and have a reduced nuclear genome
What organism has one of the smallest genomes we’ve ever seen?
microsporidian parasites
What is a mitosome?
a mitochondria that has lost all of its DNA through gene loss or transfer
it still has electron transport but does not perform oxidative phosphorylation
What is unique about Polytomella?
it is a unicellular alga that has lost its chloroplast genome
has chloroplasts still but does not perform photosynthesis
(i.e. it only has 2 genomes)
What is unique about Rafflesia?
it is a parasitic flower that has lost its chloroplast genome and therefore only has 2 genomes
it doesn’t perform photosynthesis, it sucks nutrients and water out of Tetrastigma
Give an example of a eukaryotic organism that has 4 genomes. How is this possible?
Chlorarachniophyte algae, Bigelowiella
(are actually as far from algae as us)
the 4 genomes come from a non-photosynthetic eukaryote engulfing a photosynthetic eukaryote
nuclear, mitochondrial, chloroplast and nucleomorph genomes
What is a nucleomorph?
it is what is left of the nuclear genome that was from the endosymbiont (when a eukaryotic organism is engulfed by another)
How many genomes can each domain of life have? Viruses?
bacteria, archaea and viruses - 1
eukaryotes - 1-4
What is horizontal gene transfer?
bacteria and archaeans swap genes even between VERY different species
results in a mosaic and genomes that are always changing
Does horizontal gene transfer occur in eukaryotes? Viruses?
there is probably actually a lot go HGT in eukaryotes (except for land plants and animals) and viruses
What is 1pg of DNA equal to?
1pg = 1 000 000 000bp (1Gb)
How big is the haploid human genome?
3Gb (3 billion base pairs), 3pg
How do you measure genomes? Why is this not good for large genomes?
sequence it (make contigs and assemble) not good for large genomes because repeats confuse the computer, there can be gaps, too much data, not enough reads, not enough computer power or low coverage
What is Feulgen Image Analysis Denstometry? What is it good for?
Stain the DNA using Sciff Reagent
Use a high-powered microscope hooked up to a computer to look at the pixel intensity which the computer can use (stain intensity) to estimate the genome size
good for larger genomes, usually used for nuclear genomes
Give 2 other techniques for measuring the amount of DNA in a genome and what they are good for
Gel electrophoresis, good for small pieces of DNA
DNA flow cytometry, good for larger pieces of DNA
What is DNA flow cytometry?
Use a molecule that binds to DNA that emits fluorescence and measure the amount of fluorescence
Better for larger pieces of DNA
What is the C-value paradox?
that increasing genome size does not mean increasing complexity
What organism has the smallest nuclear genome? How big is it?
Microsporidia
2Mb