Lecture 2 Flashcards by Unknown Unknown

What is LUCA?

Last universal common ancestor

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What is the first eukaryotic life?

Plants

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What is the first animal life form?

Protostomes

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What is protostomes?

Animal where mouth forms before anus.

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What is deuterostomes?

Animal where anus forms before mouth.

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What is analogous structures?

Similar structures with similar functions, but they arise from different ancestors.

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What is homologous structure?

Similar structures that arise from common ancestor but that MAY (as in not necessarily) differ in function.

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What are some approaches to study development? Name 3.

-observation
-manipulation
-model organisms

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Model organisms

Characteristics to consider (6)?

-size
-generation time
-embryo accessibility
-feasibility of genomic interrogation
-organism type in phylogenetic tree
-ease of experimental manipulation

(The best ones are easy to breed and maintain in lab)

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Model organisms

Name 4 seen in class.

-mice
-drosophila
- C. elegans
-sea urchins

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Model organisms

Reason to study mice?

Mice have evolutionary close relationship to humans.

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Model organisms

Advantages of studying mice? (3)

Mice are advantageous in studying complex diseases like cancer or diabetes. They have complex biological systems that resemble those in humans (immune, endocrine, nervous, etc.).

•The protein coding regions of the mouse and human genomes are around 85% identical.

•Genetic manipulation is harder than in other model organisms (creating mutant mice).

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Model organisms

Disadvantages of studying mice? (3)

-Expensive (mice need more supervision and maintenance than worms or flies)

•Ethical concerns

•Long generation time - 10 weeks

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Model organisms

What are some advantages of using drosophila? (5)

-Small

-fast generation time (12 days)

-large brood size

-genetic manipulation is very easy

-easy and cheap to maintain in the lab and grow at room temperature

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Model organisms

What are some disadvantages of studying drosophila? (4)

-Anatomy of the brain and other major organs are very different from humans

-can’t study behaviour

-disease states often can’t be modeled in flies

-only 50% of protein coding genes are shared with humans

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Model organisms

Advantages of studying C. elegans? (7)

-Small (1mm)

-fast generation time (3.5 days)

-large brood size (140 eggs per day)

-they are self-fertilizing hermaphrodites (no need to cross to maintain strains)

-adults and embryos are transparent

-genetic manipulation is very easy

-easy and cheap to maintain in the lab and grow at room temperature

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Model organisms

Disadvantages of C. elegans? (2)

-Simple anatomy compared to flies, mice, and humans

•Lacks a major epigenetic mark present in humans that is important in development (DNA methylation)

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Model organisms

Advantages of sea urchins? (3)

-Easy to propagate in the lab

-easy to get synchronous embryo cultures and induce embryogenesis

-the embryo is transparent and has a simple structure, rapid embryogenesis

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Model organisms

Disadvantages of studying sea urchins?

-Adult animals require a relatively large amount of laboratory space

-the time between generations can be quite long (several months) as the reproductive season is limited

-sea urchins cannot be inbred so the animals studied are genetically polymorphic

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What is a fate map?

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Graphical representation detailing fate of each part of embryo.

-so as to figure out which cell became what in the organism’s body.
-need to be able to label cells

Observation (observing embryos)

5 methods to observe embryos

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-direct observations
-vital dyes
-fluorescent dyes
-genetic labeling and chimera generation
-transgenic DNA chimeras

Observation (observing embryos)

Direct observation: 2 organisms studied in class and why?

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-C. elegans: clear embryos

-styela partita: differently coloured cytoplasms (the blastomeres that form the muscle have a yellow colour)

Observation (observing embryos)

Direct observation: who fate mapped C. elegans, and when?

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Embryonic cell lineages were mapped through light microscopy by John Sulston in 1983

Observation (observing embryos)

Direct observation: who fate mapped styela partita, and when?

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mapped by Edwin Conklin in 1905

Observation (observing embryos) Vital dyes

Dyes agar chips were placed on different parts of the amphibian embryo. The dye diffused into the tissue and the agar was removed.

Observation (observing embryos) Vital dye: disadvantages?

The dye becomes diluted with each division, making it more difficult to detect over time.

Observation (observing embryos) Fluorescent dye

Fluorescent dye can be injected into specific cells in the early embryo.

Observation (observing embryos) Fluorescent dye: why is it better than vital dyes?

Fluorescent dye will also become diluted over time but because it is so much more intense it will be visible for many generations.

Observing embryos Vital and fluorescent dyes: is a permanent or a non-permanent visualization technique?

Non permanent

Observing embryos Genetic labeling and chimera generation

a permanent visualization technique

Observing embryos Genetic labeling and chimera generation: what is a chimera?

Organism containing a mixture of genetically different tissues, formed by experimental manipulation.

Observing embryos Genetic labeling and chimera generation: how does it work?

-cells from different species express different proteins which are detected by different antibodies. -thus, you can graft cells from one organism into another and then monitor the cells from the first organism using antibodies. -(putting antibodies that detect org. 1 protein in org. 2) -after offspring is born, we can see which region of the embryo became what

Observing embryos Genetic labeling and chimera generation: disadvantages?

-most species will reject graft genes from other species -It is difficult to generate chimeras from most species.

Observing embryos transgenic DNA chimeras

Use of 2 of the same organism. Individual 1’s genes are marked with GFP, so we can follow the GFP marked gene in individual 2 when it’s transplanted onto it.

Observing embryos transgenic DNA chimeras: why is it permanent?

Because the plasmid containing GFP will be transcribed by cell. Though, the plasmid is lost after a few division, but it’s more permanent than dye.

Observing embryos transgenic DNA chimeras: what did the fate map of chicks reveal about the neural crest?

Neural crest cells are critical in making the gut neurons: The green neural crest cells migrate from the neural tube to the stomach region. Four days later, the neural crest cells have spread in the gut from the esophagus to the anterior end of the hindgut.

Observing embryos transgenic DNA chimeras: what are transgenes?

-a gene which is artificially introduced into an organism -transgenes are typically introduced into mammalian cells in the form of plasmids -when the plasmid is introduced into the cell in a process called transfection

Manipulating development mutations: how does it help with studying development?

by mutating genes, and then observing phenotypes, we can determine which gene cause/affects which body part

Manipulating development mutations: what is mutagenesis?

Formation of mutations in DNA

Manipulating development mutations: how does it affect homeotic genes?

Mutations in homeotic genes cause displaced body parts. One subset of homeotic genes are the HOX genes.

Manipulating development mutations: we can’t mutate humans, so we study birth defects. What is the difference between malformations and syndromes?

-Malformations: abnormalities caused by genetic events (gene mutations, chromosomal aneuploidy, translocation) -Syndrome: a condition in which 2 or more malformations occurs together

Manipulating development mutations: Homeotic mutations in humans Name two seen in class

-Auriculocondylar syndrome (ACS) -Synpolydactyly (SPD)

Manipulating development mutations: Homeotic mutations in humans What is Auriculocondylar syndrome (ACS)?

-mutation in genes (PLCB4 and GNAI3), that control HOX genes -lower jaw (mandible) becomes an upper jaw (maxilla

Manipulating development mutations: Homeotic mutations in humans What is Synpolydactyly (SPD)?

-mutations in HOXD13 gene - extra fingers (polydactyly) -webbed fingers (syndactyly) -Dom. mutation that affects function of other HOX genes -the same mutation in mice also causes limb defect

Manipulating development mutations: birth defects What are teratogens?

Substance that causes disruption during birth. Developing embryos has different sensitivity to different teratogens (depending on its stage). -Teratogens: chemicals, viruses, radiation -Disruptions: developmental abnormalities caused by external (exogenous) agents, not spontaneous or inherited mutations

Manipulating development mutations: teratogens Give two examples of teratogens seen in class

-thalidomide -cyclopamine

Manipulating development mutations: teratogens What does thalidomide do?

-nausea meds that can cause defect when taken 20-36 days post-conception -causes phocomelia: missing or deficiency of long boned in limbs

Manipulating development mutations: teratogens What does cyclopamine do?

- corn lily - prevents brain from separating into 2 lobes - causes cyclopia (single eye)

Lecture 2 Flashcards

(48 cards)