|
Register | Sign In |
|
QuickSearch
Thread ▼ Details |
Member (Idle past 1434 days) Posts: 20714 From: the other end of the sidewalk Joined: |
Thread Info
|
|
|
Author | Topic: "Macro" vs "Micro" genetic "kind" mechanism? | |||||||||||||||||||||||
Rrhain Member Posts: 6351 From: San Diego, CA, USA Joined: |
RAZD writes:
quote: The best example of this are the "double muscled" Belgian Blue cows. They have a genetic mutation in the myostatin gene, disabling it, which results in excessive hypertrophy of skeletal muscle cells. The bulls are so large that they tend to be incapable of breeding naturally: They would break the backs of the cows. Instead, they have to be ejaculated and the cows bred artificially or the bull needs to be put in a harness and lowered onto the cow. There is medical research done into how this can be used for human diseases such as muscular dystrophy...and worry that it would then be used as genetic doping by athletes. Rrhain WWJD? JWRTFM!
|
|||||||||||||||||||||||
pink sasquatch Member (Idle past 6051 days) Posts: 1567 Joined: |
Um, no. XO individuals develop as female. It's called "Turner's Syndrome." You are referring to an entirely different context with Turner's Syndrome, that is, the sudden loss of the Y chromosome from the human genome as it currently stands. We were discussing it in an evolutionary context, and theories that the Y chromosome is gradually shrinking, and that necessary Y genes are jumping to autosomes and gaining new regulatory mechanisms. If the proponents of this theory are correct, in a 100,000 or so human generations there may be "XO" males.
|
|||||||||||||||||||||||
pink sasquatch Member (Idle past 6051 days) Posts: 1567 Joined: |
And then there's birds where the sex chromosomes go the other way: XX individuals are male and XY individuals are female. It's my understanding that nomenclature is different when the female is heterogametic: "ZZ" males and "WZ" females.
|
|||||||||||||||||||||||
Rrhain Member Posts: 6351 From: San Diego, CA, USA Joined: |
pink sasquatch responds to me:
quote:quote: True. As my bio text puts it, birds, moths, and butterflies have this trait of the males being XX and the females being XY and "to avoid confusion, this is usually expressed as ZZ (male) and ZW (female)." And with regard to XO, I understand now what you were talking about with the genes from the Y moving to other chromosomes. Sex determination is a varied and complex thing. Bees have diploid individuals being female and haploid individuals being male. Drosophila, however, it's the ratio of X chromosomes to autosomes. That is, XXN individuals are female (that is, XXO and XXY are female) while XN individuals are male (that is, XO and XY are male). Interestingly, XO males are sterile while XXY females are fertile. And then there's grasshoppers where females are XX and males are XO. Rrhain WWJD? JWRTFM!
|
|||||||||||||||||||||||
RAZD Member (Idle past 1434 days) Posts: 20714 From: the other end of the sidewalk Joined: |
looks like there are lots of ways for 'sex' to work ... how many are independantly evolved and how many derived from other systems? Looks like the world is more wonderous the more you know.
and if you have XXY, XXO, XY and XO types which two get the free pass on the ark (assuming flies are not "clean" ... )? we are limited in our ability to understand by our ability to understand RebelAAmerican.Zen[Deist
{{{Buddha walks off laughing with joy}}}
|
|||||||||||||||||||||||
Rrhain Member Posts: 6351 From: San Diego, CA, USA Joined: |
RAZD responds to me:
quote: Well, the XO males are sterile, so they don't get to come. And if we're going to maintain the current genetic outcome, we'd need the XXY female so that the double-X gametes can be created. Rrhain WWJD? JWRTFM!
|
|||||||||||||||||||||||
pink sasquatch Member (Idle past 6051 days) Posts: 1567 Joined: |
Sex determination is a varied and complex thing... Sure is... and you didn't even get into the hermaphrodites... Rrhain - I think it was you that mentioned "lesbian" lizards in one of the many homosexuality threads - all female but reproducing sexually. Are they really more like hermaphrodites?Is it known if they have the equivalent of sex chromosomes? Would "unisexual" be an apt term for their reproduction? If there's a decent publication out there I'd like to check it out.(If I only imagined you talking about lesbian lizards, ignore me.)
|
|||||||||||||||||||||||
Rrhain Member Posts: 6351 From: San Diego, CA, USA Joined: |
pink sasquatch responds to me:
quote: No, 'twasn't me. Alas, I don't recall who and I don't have the motivation to go looking.
quote: No, they are all female. This form of reproduction is called "parthenogenesis." In the particular lizards being discussed, they cannot reproduce unless they engage in sexual activity...but this activity doesn't actually result in any genetic material being exchanged. And since all the individuals are female, they're lesbian. The sex act triggers the reproductive cycle. There is another kind of lizard that switches between sexual and parthenogenetic reproduction, depending upon the conditions the population finds itself in. When variation is needed, males start being born to allow recombination and then they go back to all female. Rrhain WWJD? JWRTFM!
|
|||||||||||||||||||||||
RAZD Member (Idle past 1434 days) Posts: 20714 From: the other end of the sidewalk Joined: |
would that make them vary sexual?
|
|||||||||||||||||||||||
Mammuthus Member (Idle past 6504 days) Posts: 3085 From: Munich, Germany Joined: |
Like cows like people...there was a kid in Germany born with a homozygous mutation in the myostatin gene..he is 5 now, built like a bodybuilder and very strong. It remains to be seen what the long term physiological effects will be on this child, but given his phenotype, there is talk of applications for muscular dystrophy i.e. compensating for the dystrophic effects by blocking myostatin production.
|
|||||||||||||||||||||||
arachnophilia Member (Idle past 1372 days) Posts: 9069 From: god's waiting room Joined: |
Rrhain - I think it was you that mentioned "lesbian" lizards in one of the many homosexuality threads - all female but reproducing sexually. nope, that was me. the lizards are the desert grassland whiptail, cnemidophorus uniparens.
Are they really more like hermaphrodites? nope. they contain only female genitalia. the process used to trigger reproduction is sexual, lizard to lizard genital contact, but the actual reproduction is technically asexual. they're cloners. all of the lizards in the population share exactly the same genes, apparently.
Is it known if they have the equivalent of sex chromosomes? yes. they're all female.
Would "unisexual" be an apt term for their reproduction? yup. "parthenogenetic unisexual pseudocopulators" is what they're called. basically, in english, it means they're virgin-birthing one-sexed mutual-masturbators. here's a link: nerve.com® as a side note, what bugs me about them isn't the lesbian sex, but asexual reproduction it triggers. these lizards don't exactly have a gene pool, per se. they're all clones, exactly alike genetically. basically, evolution has stopped for these lizards. if something were to come along that would endanger them, they'd all be gone, because natural selection for them is all or nothing. they have no way to adapt. This message has been edited by Arachnophilia, 07-12-2004 09:53 AM
|
|||||||||||||||||||||||
RAZD Member (Idle past 1434 days) Posts: 20714 From: the other end of the sidewalk Joined: |
but
each {one \ clone lineage} should be accumulating mutations and adapting in much the same way the "usual suspects" of asexual organisms adapt, and natural selection would pick the individuals to survive to breed in the same way. and population size and genetic diversity would be critical determining factors in species success. we are limited in our ability to understand by our ability to understand RebelAAmerican.Zen[Deist
{{{Buddha walks off laughing with joy}}}
|
|||||||||||||||||||||||
Mammuthus Member (Idle past 6504 days) Posts: 3085 From: Munich, Germany Joined: |
Actually, I don't think it is such a problem. Just like bacteria and other asexual reproducing organisms, the lizards will still sustain mutations subject to selection. If asexual reproduction procluded evolution we would not see as much adaptation among bacteria as we do. However, they will be much slower to respond to change as sexual reproduction is much better at spreading variation than mistakes during clonal propagation...still strange stuff in any event.
|
|||||||||||||||||||||||
arachnophilia Member (Idle past 1372 days) Posts: 9069 From: god's waiting room Joined: |
i knew i was missing something. i suppose random mutation and genetic drift through transcription errors are still in play. i should stop posting on no sleep, i must sound like an idiot lol.
although, i would imagine it still does leave them especially susceptable to extinction.
|
|||||||||||||||||||||||
Loudmouth Inactive Member |
quote: As Mammuthus pointed out above, sexual reproduction aids in the dispersal of genotypes. Bacteria, also cloners, have the advantage of multiplying quickly (eg generation time of 20 minutes) as compared to lizards which only reproduce once a year. If the population were brought to 1% of current size the whiptails would be in serious danger.
|
|
|
Do Nothing Button
Copyright 2001-2023 by EvC Forum, All Rights Reserved
Version 4.2
Innovative software from Qwixotic © 2024