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9

You might be interested in the INK4A locus (chromosome 9p), encoding both p19 and p16 genes, very close to p15. You can read a description here. All three proteins are known experimentally to exist. Now, whether these are two different genes or the same gene with alternative splicing and start sites leading to different reading frames it's up to ...


8

This is one of the most intriguing questions of eukaryotic evolution. As far as I know and have read, the autogenous theory is not accepted. There are quite some reviews on this topic. Also there is a wonderful book by Nick Lane on mitochondria called Power Sex and Suicide. You would be interested to read it. There are no sufficient evidences for the ...


7

My attempt to find an answer has suggested that no-one knows how the DNA gets into the nucleus. This fairly recent paper reports attempts to track the pathway of DNA entry and transfer to the nucleus. Le Bihan et al. (2010) Probing the in vitro mechanism of action of cationic lipid/DNA lipoplexes at a nanometric scale. Nucl. Acids Res. 39:1595-1609 ...


7

I would say it has to do with the amount of mitochondrial or sequence that has been transferred to the host genome. As a consequence of all this information stored in the host genome, mitochondria cannot reproduce without the host. In this way, they are not their own organisms, but rather organelles. Over evolutionary time, the line between organelle and ...


5

This is actually is an awesome story: both how it happens and how it was discovered. This is one of those stories people get Nobel Prize, and this was Günter Blobel who was awarded this highest possible prize for his discovery, which is according to his Nobel prize certificate: "for the discovery that proteins have intrinsic signals that govern their ...


5

This is the figure the question is about. On the right is the control experiment with GTP-γS, on the left without it: The bands that are visible in both experiments are unspecific binding. If GTP-γS doesn't affect their presence, the mechanism by which they bind to the column can't be specific to the GTPase functionality. The proteins the authors were ...


4

You asked about eukaryotes. The genome of the yeast Saccharomyces cerevisiae is 12.2 Mb. The genome of the smallest free-living eukaryote, Ostreococcus tauri (a unicellular green alga) is 12.6 Mb There are smaller eukaryotic genomes, but these are not free-living organisms they are intracellular parasites.


4

I'm wondering if it is safe to assume that the approximate number of cells per unit mass in a mammal will remain fairly constant throughout its lifespan. Not exactly. When a tissue is put under stress, it can respond in four main ways: Hypertrophy - individual cells get larger. E.g. stressed muscle cells get bigger. Atrophy - invidivual cells get ...


4

My foray into the literature suggests that mature adipocytes do not divide. See, for example: Lefterova, MI et al. (2009) New developments in adipogenesis. Trends in Endocrinology and Metabolism 20:107-114 In the context of looking at the possibility of stimulating the conversion of white adipose tissue to brown adipose tissue, the authors outline the ...


4

For starters, see this thread. My understanding is that the ancient predecessors of mitochondria were free-living unicellular organisms. Supposedly at one point, these mitochondria-like cells developed an endosymbiotic relationship with a larger cell. This relationship was advantageous for both cells: the smaller cell could focus on energy production, ...


3

In general, the compactnes of genomes is a characteristic of prokaryotes, but there are several eykaryotes that have overlapping genes: many parasites and endosymbionts. The best studied of these are the fungal parasites of the phylum microsporidia and the nucleomorphs (remnant nuclei of algal endosymbionts in cryptophytes and chlorarachniophytes). cDNA ...


3

(Reposting my comment as an answer since it seems to be what was required.) A DNA molecule that replicates independently of chromosomal DNA is an episome. By this definition a plasmid is (usually) an episome. If a plasmid integrates into a chromosome by some mechanism (as for example in Hfr strains of E. coli where the F plasmid is integrated) the plasmid ...


2

Short answer: No. Eukaryotes have more ways of maintaining telomere length than via telomerase alone and all organisms with circular genomes do not need to worry about telomere length anyway. Long answer: Firstly, the telomerase system is not the only observed mechanism in Eukaryotes that elongates telomeres. Other mechanisms such as the transposition of ...


2

Here is a study of planarian worms, which are immortal in asexual reproduction and mortal in sexual reproduction. Hydras also become mortal after they reproduce sexually. Relevant to your question: Cells within planarian worm differ in expression of telomerase active subunit depending on body part. Immortal (asexual) worms have more expression in the area ...


2

This is not my field so I am sure there are other examples, but certain neurons will definitely be larger in adulthood than in infancy. There are motor neurons that connect the spine to, for example, the toes. These will grow in length as an animal grows. So, in a human infant they will be a few centimeters long and can reach lengths of over a meter in an ...


1

You can use a bidirectional promoter. The problem that you mentioned about proteins not expressed in same level happens because of competition for polymerase. But there are well optimized parts and also commercially available vectors that work fine. You can clone genes in a serial order. It won't be a problem. Just leave a 100bp linker after the polyA ...



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