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23

Great question, and one about which there has historically been a lot of speculation, and there is currently a lot of misinformation. I will first address the two answers given by other users, which are both incorrect but have been historically suggested by scientists. Then I will try to explain the current understanding (which is not simple or complete). My ...


7

Take a look at the strategies used to sequence the wheat genome. Wheat is hexaploid. The project is described at http://www.wheatgenome.org/. For early work on the maize genome, we employed methyl filtration in order to reduce genome complexity and size - transposons are filtered out and genes + promoters and such remain. The gene sequences are different ...


4

By definition, polyploidy just means that a cell or organism contains more than 2 pairs of homologous chromosomes (or is more than 2n). This is more common in plants than it is in animals. The plant, as shown below, undergoes failed meiosis, which means that the diploid (2n) cells never become haploid (n). As a result, a plant ends up with more than 2n when ...


4

I can only offer a partial answer on the theoretical aspects. I don't know if you are familiar with the mid-90s papers by Otto et al. (Otto & Goldstein,1992, Otto & Marks, 1996), but these are definately relevant to your question. They deal with the "masking hypothesis" of diploidy, i.e. that deleterious mutations can be masked by "healthy" alleles, ...


4

Plants have a simpler anatomical structure than mammals (is anatomical the right word, or would physiological be more appropriate?). Mammals on average don't have more genes than plants, so my understanding is that this additional complexity is the result of finer and more complex regulatory mechanisms. When you remove or duplicate an individual gene in an ...


4

Yes, D. Attenborough probably refers to ploidy number Ploidy number Humans for example are 2N (except during the spermatozoid and ovule phase of human existence) meaning that they carry two copies of each autosome (=non-sexual chromosomes). Some species are 1N (haploid), some are 3N (triploid), etc… It would actually be more correct to talk about the time ...


3

I haven't seen this particular film, but other documentaries by Dr. Attenborough are very accurate and well done. In contrast to Remi.b, I'm pretty sure Attenborough referred to the ancient whole genome duplication event in land plants recently discovered in angiosperm genomes by the presence of multiple paralogous genes. The scenario is that at a certain ...


2

Ploidy and reproductive isolation in plants Speaking generally, there is simply no question that for flowering plants there can be a sexual pathway between diploid and polyploidy levels. The question is how wide is the bridge and how much flow is there in either direction. In other words the questions become "How much flow?", "How meaningful the flow?", ...


2

First of all I am not sure if your examples are per se correct. But they might also be an additional bonus. Secondly, I would like to refer to two articles: "Polyploidy" and "The advantages and disadvantages of being polyploid". One of the main benefits could be allowing organisms long-term evolutionary flexibility. Often adapted polyploids can undergo a ...


2

This is not on theoretical grounds, but here is an existence proof: a number of bacteria, which reproduce asexually, are polyploid. Here is a blog I really like informally discussing the concept of ploidy in bacteria. The example I am familiar with is cyanobacteria, which can have 3-4 all the way up to 142 copies of its genome, according to this paper (1). ...


2

In animals, polyploidy is not tolerated and very few polyploid species are known to exist. Those that do exist are usually asexual, parthenogenetic, or hermaphroditic. Most of the problems resulting from polyploidy occur during synapsis of homologues during prophase I. As plants do not have a chromosomal mechanism for sex determination, ...


1

In the genus Rhododendron polyploid species are common especially in deciduous azaleas and lepidotes. Yet complete reproductive isolation of the poylpoid species from the closely related diploid species is the exception rather than the rule. Closely related diploid and tetraploid species interact in natural contact zones to create triploids and some ...


1

Actually, that is not what is discussed in the question you linked to. The following is a quote from the very comprehensive accepted answer (emphasis mine): Polyploidy arises easily in both animals and plants, but reproductive strategies might prevent it from propagating in certain circumstances, rather than any reduction in fitness resulting from ...



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