What is hybrid DNA
Encounters with nature 8, textbook
The more similar the base sequence, the closer the relationship. The DNA (the genetic code; see page 20) provides clear evidence of the common ancestry of all living things, starting from a single primordial cell. It occurs as a genetic material in all living beings. The more closely related organisms are to one another, the more similar the base sequence of genes that carry the code for the same proteins in each case (eg insulin). However, since genes and the associated proteins are subject to selection, the comparison of DNA regions that do not code anything is more meaningful - mutations occurring here have no effect and are therefore not affected by the selection and are therefore retained. Differences in the number of mutations give an indication of the relationship - the greater the difference, the earlier the species was separated. The DNA from mitochondria is even better suited for such examinations than the DNA from cell nuclei (see page 120). The Hox genes responsible for differentiating between the various parts of the body (see page 30), which can be found in almost all animal species, also provide important clues for evolution. They form groups (clusters) on specific chromosomes in a specific sequence. The more organized an animal group is, the more Hox clusters it has. Hybrid DNA breaks down at lower temperatures than the DNA double helix Another method of determining relationships is to compare the temperature at which hybrid DNA breaks down into single strands. Temperatures of 80 ° C to 90 ° C are required to separate the DNA double helix (releasing the hydrogen bonds). The strands reconnect as they cool down. If you isolate the individual strands beforehand and bring the corresponding individual strands of different organisms together (eg human and chimpanzee), these also connect when they cool down. Since not all bases in this hybrid DNA have a complementary one, there are fewer hydrogen bonds in the double strand. If it is heated again, this can therefore be separated earlier, i.e. at a lower temperature. The more bonds there are between the individual strands, the higher the separation temperature and the more closely related the living beings tested are. Mutations Every different base is the result of a mutation. The more bases that differ, the more mutations have already taken place, which means that the longer the line of development was separated. Hox clusters were created on several chromosomes in the course of evolution through duplication from originally one cluster 56 Who are we more closely related to? Chimpanzee or ... 57 ... gorilla? 58 DNA hybridization Active yourself! A human-chimpanzee hybrid DNA separates into single strands at around 86 ° C. The temperature at which a human-gorilla hybrid DNA is split into single strands is about half a degree Celsius below. What do you conclude from this? Workbook page 35, 38 M 115 Evidence for the evolution of living beings For testing purposes only - property of the publisher öbv
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