17 - Development

Question 1

Identify the various mechanisms for regulating the activity of mRNA after they are transcribed.

Answer 1

• Variations in pre-mRNA processing can regulate which proteins are made in cells
• some posttranscriptional controls operate by means of masking proteins that bind to mRNAs abd make them unavailable for protein synthesis.
• The rate at which eukaryotic mRNAs break down can also be controlled posttranscriptionally.
• noncoding single-stranded RNAs that can bind to mRNAs and affect their stranslation

Question 2

Identify the various mechanisms for regulating the activity of proteins after they are translated.

Answer 2

• through chemical modification
• processing
• degration

Question 3

typical causes of cell death.

Answer 3

• Juveniles hatch and parental somatic cells die (volvox)
• Causes of (cell Death)
  
  • Maybe the chlamy cell would eat itself (lysosomes)
  • The cell could grow too much and might starve
  • Virus
  • Might commit suicide
  • Environmental issues, protein gets denatured
  • Maybe you get eaten
  • Maybe it is more beneficial to be dead
  • When it reproduces the daughter cells could kill the parent cell

Question 4

• mechanism of plasmid toxin/antitoxin system as a possible origin for cell death genes.
• possible evolutionary origin of programmed cell death genes.

Answer 4

• Some plasmid codes for their on transfer from one cell to another
• Cells might try to get rid of them, when dividing one daughter cell might not have that plasmid
• The plasmid carry a toxin gene, that says if you get rid of me you die
• The half life to the toxin is very long, the anti-toxin is very short
• The cell that doesn’t have the plasmid will quickly die
• You want to get a hold on that anti-toxin gene, and the host gets a hold of it and now it can make an anti-toxin, but the plasmid makes new toxin, which becomes an arms race
• Programmed death could have happened for these reasons
• Cells might have coopted this toxin anti-toxin to commit suicide when the cell might have a virus
• By parasitic plasmids

Question 5

programmed cell death cascade in C. elegans.

Answer 5

• It is an reversible very controlled biochemical pathway that results in cells dying
• It is a result of a signal that comes from outside
• CED-9 inhibits CED-4
• Posttranslational control of protein function
• The death signal is some kind of hormone
• CED-4 activates CED-3 it is a caspase that digests other proteins, which then turns it to an active protease
• It maybe be turned on by providing a code factor, or changing the shape, adding/removing a chemical group, provides enzymes to work properly
• In silico (on computer) methods have identified caspase orthologues in bacteria…

Question 6

characterisitics that make Drosophila an attractive model system.

Answer 6

• is easy to culture. Grows at 25°C in small bottles stopped with a cotton or plastic foam wad and about one-third filled with a fermenting medium that contains water, cornmeal, agar, molasses, and yeast.
• the several hundred eggs hatch rapidly and progress through larval and pupal stages to produe adult flies in about 10 days.
• Many types of mutaions produce morphological differences, such as changes in eye colour, wing shape, or the numbers and shapes of bristles, which can be seen with the unaided eye or under a low-power binocular microscope.
• giant chromosomes in larvae that make it easy to observe differences with a light microscope.

Question 7

main stages in Drosophila embryonic development.

Answer 7

• Eggs has one nucleus, the nucleus divides but the cell does not
• The fruit fly genome make to organism, the larva, and the fly
• How could you discover the genes involved in development
  
  • Through comparison genetics
  • Mutations, barbie and ken
• The are genes involved in helping the embryo know its direction
• The drosophila egg is vey highly ordered

Question 8

main role of maternal effect, segmentation and homeotic genes in Drosophila development.

Answer 8

• When the mother make the egg and packs it full with citoplasm and makes it with mRNA that is not translated, by binding proteins, so it doesn’t get translated until fertilization
• After fertilization the mRNA gets translated. The gradiant is very important in the development.
• Maternal-effect genes determine polarity, the next set of genes divides the embryo into segments
• The next set of genes tells the segments what to do, grow in to legs wings
• Sometime there is a mutation in the genes, homeotic genes, this changes the segment growth

Question 9

structure/function of the “homeobox” in homeotic genes

Answer 9

• They are transcription factors
• The homeobox is a sequence in the proteins that bind in the DNA
• These proteins are transcription factors
• All the coloured genes are the homeotic genes
• There has been duplication of these genes
• They could have evolved to make new different segments
• The homeotic genes appear in the same order as it is expressed in the embryo, this is the same all over the animal kingdom
• Conservation of gene structure, gene expression, gene order over time, Hox (homeobox containing gene) genes are evolutionarily conserved

Question 10

role of programmed cell death in Drosophila development

Answer 10

• In the transition of a worm to a fly, the larval tissue has to die
• Programmed cell death gets rid of this
• A death signal causes the tissue to die
• Comes from a hormone ecdysone
• Inside there are little sac of cells that turn to leg and wings
• When studying it you find a lot of similar motives of death
• When grim and reaper are turned on cells die
• The reaper gene: transcriptional region is very sensitive to ecdysone, if p53 detects damage then the gene is turned on
• Its is under the control of many signals, that control the death of the organism