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Questions for Bio Sci Fi

September 19, 2012

Teaching full time again, I don’t get to update as often. I thought you might enjoy some of the questions my students are working on for Biology in Science Fiction.

1. Pandora isn’t the only place where people are blue. There is a real genetic condition of “blue people,” who lead normal lives. Here is their pedigree (above).

A. Is the blue condition dominant or recessive?

B. In the pedigree, who do you think carries two different alleles? (one dominant, one recessive) Name three individuals.

2. Suppose you are a genetic counselor. A couple comes to ask you about cystic fibrosis, an inherited recessive disorder with lifelong complications of breathing and digestion.

A. Both members test positive that they carry a recessive allele.  What do you tell them is the likelihood that their child will have the disease?  Explain.

B. Suppose the couple have two children. What is the chance that both will have cystic fibrosis? Explain.

C. Suppose the couple already have two children with the disease. The parents then come to you and ask: What is the chance that our next child will also have the disease?  Explain.

3. Dr. Augustine is studying the prolemuris population of Pandora. She compares the DNA of a large number of prolemuris offspring with that of their parents. Offspring of a 7-year old prolemuris have 20 mutations compared to the parent, whereas offspring of a 12-year old prolemuris have 30 mutations compared to the parent.  Assuming the mutation rate increases exponentially, what is the doubling rate of mutations in Prolemuris?

4.  Suppose some people evolved the ability to absorb solar energy through photosynthesis, besides eating food.

a. What kind of evolution would generate people who resemble plants?

b. Would these people be able to interbreed with plants?

c. Do you think they would be human?

12 Comments
  1. September 19, 2012 5:49 pm

    We feel sympathy for humans in a vegetative state, so plants would probably feel sorry for their comrades in a ‘human’ state. Human is a word as complex to define as ‘soul’, but my opinion is that any organism that can pass a Turing test will be considered human for most purposes.

    • September 20, 2012 8:45 pm

      True, although as I recall even the infamous Eliza shrink program passed the Turing test for some people. I’ve always thought the Turing test might be too easy.

  2. paws4thot permalink
    September 20, 2012 5:39 am

    4B) I’d be dubious, unless their biology was sufficiently plantlike that they could breed by grafting parts of a plant to themselves ot parts of themselves to plants, rather than solely by fertilisation. After all, a human can’t breed by coitus with, say, a dog, or a rose be fertilised with tomato pollen.

    4C) First, give your definition of the term “human” surely?

    • September 20, 2012 8:46 pm

      Part of the point of the question is to get students started thinking how THEY define the term human. It gets a lot harder from here on (chimp hybrids, cyborgs and androids, Oh My.)

      • paws4thot permalink
        September 21, 2012 4:25 am

        Yes, I got that. My point was that, in order to answer the the question you first have to state your definition, or student and tutor have to have a shared definition.

  3. SFreader permalink
    September 20, 2012 8:00 pm

    Q4- A planet where the CO2/O2 balance has large, quick swings would favor a human-plant respiratory. Humans still use their skin for some of their respiration but still – like lungs- the input is O2, so you’d need to make the pores specialize in CO2 while the lungs would continue to specialize in capturing/using O2 as their. This would probably require a whole mess of similar changes at the cellular level throughout the body.

    I think that ‘breeding’ would mostly require compatibility of the reproductive systems, hormones, antibodies, etc. as even genetically very similar mammals (humans included) can be reproductively incompatible. Whether you’re breeding for fertile or sterile progeny would also impact how much/what tweaking would be needed.

  4. SFreader permalink
    September 20, 2012 8:05 pm

    Hi there:

    Every once in a while – like today – this Web page goes crazy on me,i.e. starts scrolling up and refuses to go and stay at the bottom of the page … makes it really difficult to see/type anything.

  5. September 20, 2012 8:49 pm

    Question 3 is the one that fascinates me. If most primates (like humans) experience exponential rise of mutations in the male, then maybe that explains why most primate females (such as chimps and baboons) actually prefer younger males (not the alpha male) to sire their offspring.

  6. heteromeles permalink
    September 26, 2012 2:09 pm

    I like question 4, but I don’t know if you’ve been covering life cycles that much.

    4. Suppose some people evolved the ability to absorb solar energy through photosynthesis, besides eating food.
    –Fundamental problem here is that photosynthesis as we know it comes from cyanobacteria, so it’s not evolution so much as endosymbiosis. I don’t think that can happen artificially, but perhaps a parasitic cyanobacteria somehow evolves (unlikely) and then fails to kills its host.

    a. What kind of evolution would generate people who resemble plants?
    –Presumably you’re looking for convergent evolution, but the basic issue is that a photosynthetic organism needs to maximize surface area if that’s how they are going to fix enough sugars to live on. Plants have probably the best set of terrestrial designs for that particular application

    b. Would these people be able to interbreed with plants? Um, no. You could have some real fun (a la James Tiptree) pointing out the sporic life cycle of plants. If humans had a sporic life cycle (multicellular haplohumans and diplohumans in alternating isomorphic generations) would you rather be a haplohuman or a diplohuman? I used to ask that question in general botany, because it was a great way to see if students understood the concept of alternation of generations. Those who didn’t understand would look at me blankly, while those who got it would have this interesting look on their faces. Personally, I’d be happier as a haplohuman, but I’ll leave that to the audience to figure out why.

    c. Do you think they would be human? Sure. Why not? If the plastids are acquired by infection, we don’t necessarily consider infected people to be non-human, zombies and werewolves aside. If the plastids were acquired by choice, I’m pretty sure that most people wouldn’t become photosynthetic unless they could maintain their previous rights as humans. It’s not a cool enough mod to have to make up for a lack of basic human rights.

    • September 26, 2012 3:40 pm

      Cyanobacteria: Actually, cyanobacterial (and algal) endosymbiosis has evolved many times in protists and invertebrates such as hydras and marine worms. So it’s not a bad stretch for human phagocytes.

      Surface area: There are mutations that cause extra folds of skin, so maybe surface area could increase. In any case, in this problem the photosynthesis is supplementary to the diet.

      Interbreed: I wouldn’t want to be a haplohuman; too little genetic diversity, weakened immune system.

      Human: Sure hope so. It’s chilling, though, to realize how little difference is enough to make people doubt someone’s human.

  7. heteromeles permalink
    September 27, 2012 3:57 pm

    Hi Joan, far be it from me to correct you, but just a wee bit about that alternation of generations thing that plants do? They go from haploid to diploid to haploid to diploid etc.

    The diploid generation produces haploid spores through meiosis, which grow up to be haploid plants. Haploid plants produce eggs and sperm through mitosis, and these fuse through syngamy to form a diploid offspring.

    Now, if humans had this form of life, diplohumans would all be female, producing haplomale and haplofemale offspring pretty much automatically, although nursing might delay the next pregnancy. Since we’re talking about humans, I’m assuming that when the four haploid zygotes form through syngamy, three of them typically abort, so that the diplo-woman doesn’t have to carry quadruplets with every pregnancy.

    Haplomales and haplofemales, of course, get to breed. Their diploid children will be clones of each other and all female. Since I’m not to fond of the idea of being continually pregnant throughout my adult life, I’d rather be haploid.

    For this scheme to work, of course, humans would have to ditch the XY sex scheme for some other method, perhaps something akin to the ZW system seen in Komodo dragons with the exception that having a single Z or a single W isn’t fatal.

    One final note: almost all fungi and all mosses are haploid, and they’ve been around for a very long time. The idea that haploids are weak is kind of…what’s the polite word? There isn’t one, really. Anyone who thinks diploids are inherently better really is being human chauvinist, sorry to say. In humans, one copy of each gene is typically silenced in any case, so it’s highly unlikely that a haplohuman would be at a significant disadvantage compared to a diplohuman, in this system anyway.

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