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- Why do we resemble our parents? by bella bella on Prezi
Watson, an American 23 year-old biologist, and Crick, an English 35 year-old physicist, worked in the Cavendish Laboratory in Cambridge. Watson and Crick, after present a wrong model of the triple helix, told Maurice Wilkins about what they were trying to do and he showed them a new and better X-ray picture of DNA, which had been taken by Rosalind Franklin, without her permission. This was the picture number 51 to help them solve the mystery Figure 5. This day is called for someone the 8 th day of Creation.
The 25 th April it published their article with words in Nature Figure 6. Three years earlier had published law Chargaff , which was one of the foundations to apply the theory of the double helix of DNA. This law establishes the complementarity of the bases in DNA, i. So the amount of purine A and G is equal to the amount of the pyrimidine T and C. It has been argued that the discovery of DNA as well as our understanding of its structure and function may well be the most important discovery of the last century. The effect of the discovery of DNA on scientific and medical progress has been enormous, whether it involves the identification of the genes that trigger major diseases or the creation and manufacture of drugs to treat these devastating diseases.
In fact, the identification of these genes and their subsequent analysis in terms of therapeutic treatment has ultimately influenced science and will continue to do so in the future.
While the discovery of DNA has been a significant one in the twentieth century, it will continue to revolutionize medicine, agriculture, forensics, paternity and many other important fields in society today. DNA research encompasses an evolving area of progress and continued funding and interest in its relevance will likely fuel new discoveries in the future. Esteu comentant fent servir el compte WordPress.
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Biology, Answering the Big Questions of Life/genetics1
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Apreneu com es processen les dades dels comentaris. Figure 1. Human female karyotype, i. Figure 2. Figure 3. Figure 4. This is true for pretty much all animals. In plants and fungi too, mitochondria come from one parent only, although not necessarily from the mother.
Why do we have two different kinds of inheritance, one for nuclear genomes nDNA that combine parts of the mother and the father, and one for mitochondrial genomes, that excludes one parent completely? The reason behind the evolution of so-called uniparental inheritance has long been a mystery among evolutionary biologists. One thing was clear: it better be for a good reason. Mammalian males go through the bother of actually tagging the mitochondria in their sperm so that it is easier to destroy them after the egg has been fertilised.
In plants too, the mitochondria from one parent are actively destroyed, this time before fertilisation takes place. The idea is that mtDNA replicates independently within the cell, so the number of copies increases over time. And the more copies there are, the more likely some will be transmitted to the daughter cell when that cell divides.
Why do we resemble our parents? by bella bella on Prezi
If all mtDNA comes from one parent only, then mtDNA within a cell are closely related to each other, as they are all clones. Hence, there is not much scope for competition, as copies of the mitochondrial genomes are basically competing with exact copies of themselves. But imagine what could happen if organelles were derived from both parents, the four grandparents, and so on ad infinitum. This would set the scene for a genetically variable population of organelles in every cell. And this could be bad news as now different clonal lineages of mtDNA are competing with each other.
The faster mtDNA replicates, the more copies it produces and the more likely it will spread to the next generation of cells. Ultimately, the slower reproducing organelle lineage will be eliminated from the cell lineage. Thus, competition among organelles within cells selects for smaller genomes.
At some stage genomes will be so small that the function of the organelle is affected. Remember that the mitochondria produce the energy the cell needs, so when their genome size becomes very small, the organelles cease to function properly and the host cell suffers.
Recently a much simpler explanation was proposed: what if the simple mixing of mitochondrial lineages within the same cell is for some reason costly in itself? This very simple assumption actually nicely explains the peculiar inheritance of mitochondria in theoretical models.
But there is more. Mice that were experimentally constructed so that individuals carried two mitochondrial lineages were less active, ate less, were more stressed and were cognitively impaired. It seems carrying mitochondria from both your parents is bad for you. So why is the question of whether you are more like your mum or dad so hard to answer? Because your genetic make-up is only part of the equation. Which genes are expressed is the other part. And apparently your dad has the upper hand when it comes to which genes are expressed. So, you may look more like your dad but are more related to your mum after all.