Mutations
Mutations are random changes in the DNA code. The DNA code consists of many codons (chemicals separated into groups of three). The two main types of mutations are point mutations and frame shift mutations.
Point mutations are either missense, nonsense, or silent mutations. In each case, one chemical is substituted for another when the DNA is copied. When a missense mutation takes place, the changed chemical produces a codon for a different amino acid than the original. In the event of a nonsense mutation, the chemical changed creates a “stop codon” before the entire protein is fully made. In a silent mutation, the changed chemical does not alter the amino acid produced by the codon, so the mutation is a symptomatic.
Frame shift mutations offset the grouping of the codons. There are two types of frame shift mutations: insertion and deletion. In an insertion mutation a chemical is inserted into the strand of codons. In a deletion mutation, a chemical is deleted from the strand of codons. Both result in a shift in the line of codons, which creates a different set of codons and therefore, different amino acids. Sexual Reproduction:
During sexual reproduction a combination of the genetic material of both parents is passed on to the offspring. Meiosis is the process, which happens in the nucleus, through which new sex cells are made. First, both chromosomes of the pair are duplicated. Then, “crossing over” takes place. This is a process during which pieces of chromosomes switch with each other, making each of the four chromosomes slightly different. Each of these four chromosomes then ends up in a separate sex cell (called a daughter cell). Meiosis is a random process, which leads to millions of possible variations in offspring. (See figures 1 and 2)
Genetic Drift
Genetic drift is when an entire population of a species, with specific characteristics, is wiped out due to a natural disaster such as a volcanic eruption, tsunami, hurricane, earthquake, drought, or flood. Chance plays a huge role in this because natural disaster cannot be controlled and the likelihood that any population will get wiped out is the same (assuming there are natural disasters which usually occur in an area). Both well-adapted and poorly adapted organisms in a population suffer equally from genetic drift.
When a population is completely killed off, there are no more genes available for selection for that species in that location, of course. When this happens populations of that species migrate to that location and all of a sudden there is a great variety of alleles in that particular location. As these organisms with variations mate with one another more variation is produced and natural selection takes place among those individuals.
Gene Flow
Gene Flow is the process of genes moving from one population of a species to another through migration. When a population of a species with a particular gene for a specific characteristic comes in contact with another population of the same species, there are then two possible alleles that can be passed down. When these two variations of the same organism mate, the variation in the offspring will increase. At that point, natural selection will take its course and the organisms with the traits better adapted to their environment will be more successful at living and reproducing. These traits could be the ones originally there, the new ones, or a combination of the two. (See figure 3)
Natural Selection
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