Among the great discoveries of the 20th century was that of the role of DNA in heritability and the maintenance of life. Each of our cells contains almost two meters (6.5 ft) of DNA coiled within it. The study of DNA is still ongoing, but some of the discoveries so far have been a bit weird.
Hybrid Vigor
We all know the dangers of inbreeding and that it is probably not best to marry a close relative. Charles II, the king of Spain in the late 1600s, was so inbred that instead of the usual eight great-grandparents, he only had four. A glance at his portrait and biography will show that this was not a good idea.But something interesting happens when you breed two inbred individuals from different families together. The offspring of such a match will often show a level of physical fitness well above either parent, and sometimes greater than the general population. This effect is called heterosis, or hybrid vigor. What seems to happen is that, for an inbred individual to survive, they must have some valuable traits to offset the detrimental ones. An individual who has been inbred from a different family will have different sets of genes. The cross will benefit from the good dominant traits and hide the negative recessive traits. This also explains the current trend of crossbreeding purebred dogs.
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Epigenetics
Just when you think you have genetics figured out, a new set of complications arises. You inherit one copy of a gene from your mother and one from your father, and you would think they would interact in a nice, equal style. Alas, the inequality between the genders is more than skin-deep.Epigenetics is the study of the changes which can be made to DNA without changing the actual sequence of the DNA itself. Chemical modifications to the DNA can make a gene more or less active. This imprinting, as it is called, can have large effects on offspring health. Two disorders—Angelman syndrome and Prader-Willi syndrome—are caused by the inheritance of the same genetic information, but they have widely differing symptoms. The same DNA sequence causes different effects, and it all depends on whom you inherit that piece of DNA from. If the DNA is from your mother, you will develop Prader-Willi syndrome. If the DNA is from your father, you will develop Angelman syndrome.
Mosaicism
It is often said that the DNA in all of our cells is the same. This is broadly true, except in the case of mutations. If a mutation happens when an embryo is young, say eight or 16 cells, then all of the descendants of the mutated cell will inherit the mutation. This will lead to patches of the adult organism having the mutation while others don’t. This can lead to visible changes, such as patches of colored skin or hair, or localized diseases. In humans it can be possible to see stripes (called Blaschko’s lines) that occur when two colored cell types develop together.Occasionally it happens that two embryos in a womb will fuse at an early stage of development. The cells of the two embryos mingle and develop as a single individual. That one organism will then have two sets of DNA. Due to cell migration in embryo development, the resulting organism will end up with patches of each type of cell. In this case of mosaicism, the organism is referred to as a chimera.
Repeats
Proteins are coded for in DNA in sections of three base pairs in length (codons). When DNA is copied there is a proofreading process which makes sure that the copy is the same as the original. Mutations occur when a mistake slips through the proofreading, an event which only happens about once every several million base pairs. But certain sites are more likely to accumulate mutations than others. Sometimes there are repeated runs of the same codon, called trinucleotide repeats. These make it harder for the proofreading mechanism.In Huntington’s disease, the gene involved has a number of runs of CAG in its code. If during copying an extra set of CAG base pairs is slipped in, the proofreading mechanism might miss it, as there are CAG repeats on either side. As a result, when the protein is produced, it has an extra amino acid in it. Luckily there is some flexibility in the protein which allows for some additions. Only when the length of the mutation reaches a critical length does the disease show. And because mistakes accumulate with each generation, Huntington’s disease appears to get worse from parent to child.
Hybrid Vigor
We all know the dangers of inbreeding and that it is probably not best to marry a close relative. Charles II, the king of Spain in the late 1600s, was so inbred that instead of the usual eight great-grandparents, he only had four. A glance at his portrait and biography will show that this was not a good idea.But something interesting happens when you breed two inbred individuals from different families together. The offspring of such a match will often show a level of physical fitness well above either parent, and sometimes greater than the general population. This effect is called heterosis, or hybrid vigor. What seems to happen is that, for an inbred individual to survive, they must have some valuable traits to offset the detrimental ones. An individual who has been inbred from a different family will have different sets of genes. The cross will benefit from the good dominant traits and hide the negative recessive traits. This also explains the current trend of crossbreeding purebred dogs.
Lenovo uk Support
Epigenetics
Just when you think you have genetics figured out, a new set of complications arises. You inherit one copy of a gene from your mother and one from your father, and you would think they would interact in a nice, equal style. Alas, the inequality between the genders is more than skin-deep.Epigenetics is the study of the changes which can be made to DNA without changing the actual sequence of the DNA itself. Chemical modifications to the DNA can make a gene more or less active. This imprinting, as it is called, can have large effects on offspring health. Two disorders—Angelman syndrome and Prader-Willi syndrome—are caused by the inheritance of the same genetic information, but they have widely differing symptoms. The same DNA sequence causes different effects, and it all depends on whom you inherit that piece of DNA from. If the DNA is from your mother, you will develop Prader-Willi syndrome. If the DNA is from your father, you will develop Angelman syndrome.
Mosaicism
It is often said that the DNA in all of our cells is the same. This is broadly true, except in the case of mutations. If a mutation happens when an embryo is young, say eight or 16 cells, then all of the descendants of the mutated cell will inherit the mutation. This will lead to patches of the adult organism having the mutation while others don’t. This can lead to visible changes, such as patches of colored skin or hair, or localized diseases. In humans it can be possible to see stripes (called Blaschko’s lines) that occur when two colored cell types develop together.Occasionally it happens that two embryos in a womb will fuse at an early stage of development. The cells of the two embryos mingle and develop as a single individual. That one organism will then have two sets of DNA. Due to cell migration in embryo development, the resulting organism will end up with patches of each type of cell. In this case of mosaicism, the organism is referred to as a chimera.
Repeats
Proteins are coded for in DNA in sections of three base pairs in length (codons). When DNA is copied there is a proofreading process which makes sure that the copy is the same as the original. Mutations occur when a mistake slips through the proofreading, an event which only happens about once every several million base pairs. But certain sites are more likely to accumulate mutations than others. Sometimes there are repeated runs of the same codon, called trinucleotide repeats. These make it harder for the proofreading mechanism.In Huntington’s disease, the gene involved has a number of runs of CAG in its code. If during copying an extra set of CAG base pairs is slipped in, the proofreading mechanism might miss it, as there are CAG repeats on either side. As a result, when the protein is produced, it has an extra amino acid in it. Luckily there is some flexibility in the protein which allows for some additions. Only when the length of the mutation reaches a critical length does the disease show. And because mistakes accumulate with each generation, Huntington’s disease appears to get worse from parent to child.
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