Biology 1002B Study Guide - Midterm Guide: Insertional Mutagenesis, Chlamydomonas, Genome Size
16 Jun 2018
School
Department
Course
Professor
CLASS 1
Single celled Eukaryotes with a nucleus and a mitochondria that move around and are classified as Green
Algae. They are distantly related to plants b/c it has a huge chloroplast.
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Its considered a model system because it performs metabolic reactions via photosynthesis and can grown in
both liquid and water.
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A "planimal" has attributes of both plants and animals in its genetic sequence.
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What is Chlamydomonas, its major features?
An organelle found in the flagella of unicellular photosynthetic organisms (i.e. chlamydomonas) that plays
the role of a photoreceptor. It also control phototaxis, which is the bodily movement of an organism to light.
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What is the eyespot?
Uses light energy to perform photosynthesis and perform metabolism. The eyespot allows for positive
phototaxis.
1.
Uses light to get a sense of the environment around it
2.
What two ways does Chlamy use light energy?
A genome is a haploid set of chromosomes. The complete set of genes or genetic material present in a cell
or organism. We compare genome size by comparing haploid sets. Chlamydomonas have 3 genomes.
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Mitochondrial Genome
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Nuclear Genome
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Chloroplast Genome
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There are 3 sets:
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What is a genome, how many does Chlamy have, where are they found?
Open Reading Frame is a sequence of DNA that is predicted by reading a protein coding gene. They start
with a certain sequence of DNA nucleotides and end with one of the termination sequences.
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What is an ORF (open reading frame).
Photosynthesis takes place in chloroplasts, so possessing a chloroplast allows an organism to be
photosynthetic.
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Relationship between photosynthesis and possessing a chloroplast.
Phototaxis is the movement of an organism in response to light. Positive phototaxis is moving towards the
light source and negative phototaxis is moving away from the light source.
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Define phototaxis...negative versus positive
Relationship between ORF and Genome Size
A change in the double stranded sequence of DNA.
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Define mutation
Mutagenesis: the process by which the genetic sequence of DNA is changed causing mutation.
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Insertional Mutagenesis: is when a giant hunk of foreign DNA sequence is inserted in the original DNA
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Define mutagenesis, insertional mutagenesis
Cycle 1 outcomes
January 11, 2018
2:25 PM
Bio 1002B Page 1
Insertional Mutagenesis: is when a giant hunk of foreign DNA sequence is inserted in the original DNA
sequence, disrupting the function of the original sequence.
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Producing a mutagenized population of Chlamy cells allows to see the evolution of Chlamy over time. Study
antibiotic resistance, the evolution from single to multicellularity, phototaxis etc.
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Why would one want to produce a mutagenized population of Chlamy cells?
To study the function of the gene and then aid in developing antibiotics against the bacteria
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Advantages to using an antibiotic resistance gene as the insertional mutagen.
Mix a sample of cells with a foreign gene and electrocute them
1.
Mix them on an agar plate containing antibiotic
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Observe! The ones that survive have been successfully implemented with the antibiotic resistance gene.
3.
Wild type cells + antibiotic resistance gene ---> electroporation ---> membrane opens up, in two weeks put
on plate with mix of agar containing antibiotic
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Basic steps in electroporation-mediated mutagenesis.
It is not very efficient
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The insertion of antibiotic resistant gene occurs randomly
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Ideally 1 insertion per cell
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With electroporation....how efficient is it, how random is it, and how many inserts per
nuclear genome would one expect?
The goal of screening is to see the function of a mutant gene by observing and identifying the odd one out of
a population (a difference in phenotype) and comparing it to the majority of the population.
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After mutagenesis comes screening...What is screening....what is its goal? How would
one screen for phototactic mutants.
MENTAL FLOSS
Simply life cycle, genome
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Easy isolation of mutations
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Single celled, 2 flagella, eukaryotic (more closely related to animals)
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Uses light for 2 different things (photosynthesis, movement)
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Shares genes with eukaryotes/ prokaryotes
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Comes off branch which leads to land plants…
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What characteristics does Chlamy have that makes it a "model system" for
experimentation?
Means only 1 copy of gene therefore if it is malfunctioning you would clearly see the difference it makes in
the phenotype
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However, if the organism was diploid, there would still be the possibility of having another copy of the gene
to rely on/ the gene may not be knocked out completely.
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More work in knocking out all 4 alleles rather than just 2 alleles of specific gene
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Because the mutant allele will always be expressed. There's no dominant (or wild type) allele to
suppress the effect of the mutant allele, since the haploid organism would have only one set of
chromosomes and thus only one allele per gene locus.
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What are the advantages/disadvantages of being haploid for our mutagenesis
approach.
Photosynthesis (can possibly become damaged from too much light exposure with the creation of free
radicals, or not get enough light for conducting photosynthesis)
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Movement (eyespot would have difficulty or it would be unable to conduct proper movement because of
insensitivity to light
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Come up with a list of specific genes/processes that could be disrupted in cells that are
unable to display phototaxis.
CLASS 2- pre lecture reading, CLASS 2
Earth is 4.6 billion years old
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How old is the Earth, and when do we think life developed.
Bio 1002B Page 2
Earth is 4.6 billion years old
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Life originated 4 billion years ago
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There is fossil evidence to show that life originated 3.5 billion years ago
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Sediments of the ocean floor have lower levels of carbon-13 than expected meaning this may be due
to deposits of dead plants that take in and are made of mostly carbon-12
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Early photosynthetic take CO2 from atmosphere and synthesize organic compounds
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There is chemical evidence that shows life may have originated 3.9 billion years ago
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A type of layered rock that is formed when microorganisms bind particles of sediment together, forming thin
sheets.
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They are the earliest conclusive evidence of life found in the fossilized remains of structures
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Modern day stromatolites are formed by layered growth of cyanobacteria
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It provides evidence of microbial activity during primitive earth
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What are stromatolites
Banded iron and stromatolites are "biosignatures" what do we know about how life is
linked to their formation?
Cyanobacteria is what left these biosignatures and proves that primitive earth was anaerobic and lacked oxygen
and then O2 levels increased due to microbial activity, and that life originated about 4 billion years ago
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Stromatolites provide the evidence of life originating about 4 bya based on geological evidence and dating of
fossilized remains of stromatolites
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The banded iron on sedimentary rocks gave the evidence of primitive life once being heterotrophic and anaerobic,
where fermented pathways were used to extract energy from organic molecules such as water. When
cyanobacteria used H2O to get electrons for photosynthesis, the released Oxygen reacted with Iron in water
forming a red-coloured precipitate and overtime the excess oxygen accumulated in the environment and gave
evidence of increased O2 levels.
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Abiotic synthesis
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Heritable information
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Metabolism
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Formation of cells
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What are the four major developments that need to take place to make a living cell.
Geological stage - Earth/ atmosphere comp.
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Chemical - life’s building blocks
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Biological - organization into living cells
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Three stages of prebiotic evolution, how much is known about each.
It contained a lot of water vapour, hydrogen gas, methane, carbon dioxide and ammonia allowing for a
lot of reduction (using the electrons from these molecules for other reactions) to occur. This in the end
allowed for the development of complex molecules
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The primordial atmosphere was a reducing atmosphere
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The current atmosphere is oxidizing because there is a much higher level of oxygen present in the
atmosphere, therefore, the formation of new complex molecules is not suited because Oxygen is an
oxidizing agent and takes electrons, instead of providing electrons, therefore making it difficult to form
complex molecules without sufficient electrons.
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Conditions in the primordial atmosphere, why were they conducive to the development
of complex molecules
Laboratory simulation of primordial earth's reducing atmosphere, put in place to prove how certain organic
molecules( amino acids, Urea etc.) were created under these early earth conditions.
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Conditions created several abiotic molecules that are necessary for life today. It did not, however, show that
primordial atmosphere actually contained all these gases (Hydrogen, Methane, Ammonia etc.) needed to
form such complex molecules.
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Volcanic analysis suggests that Earth was probably less reactive, containing gases such as Nitrogen, Carbon
monoxide, and Carbon dioxide. Regardless, laboratory experiments have shown that even with an
atmosphere such as the one suggested by the geologists, crucial building blocks of life can still form
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COULD NOT EXPLAIN: how polymerization occurred, homochirality (L amino acids, D sugars) because it only
produced monomers and a racemic mixture (50% of each chiral molecule).
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What was the Miller-Urey experiments. What did it show, didn't show.
What is chirality, why is it important. Homochirality
Bio 1002B Page 3
Document Summary
Single celled eukaryotes with a nucleus and a mitochondria that move around and are classified as green. They are distantly related to plants b/c it has a huge chloroplast. Its considered a model system because it performs metabolic reactions via photosynthesis and can grown in both liquid and water. A planimal has attributes of both plants and animals in its genetic sequence. An organelle found in the flagella of unicellular photosynthetic organisms (i. e. chlamydomonas) that plays the role of a photoreceptor. It also control phototaxis, which is the bodily movement of an organism to light. Uses light energy to perform photosynthesis and perform metabolism. Uses light to get a sense of the environment around it. A genome is a haploid set of chromosomes. The complete set of genes or genetic material present in a cell or organism. We compare genome size by comparing haploid sets.
