The Science of Genetics
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Genetics is the study of heredity or the study of how traits are passed from parents to offspring. This study is largely based on genes. Genes are structures found in every single cell that contain information about traits that an organism has or carries. Genes are a blueprint of what an organism will look like, how it survives, and how it reacts to its environment. Genes give organisms of a species a means for variation. Genes are chained together in a double helix called DNA. DNA in turn forms chromosomes. Chromosomes come in pairs and different species have a different number of these pairs. This is one of the things that make organisms from one species look different from other species. Humans have 23 pairs of chromosomes. Each gene contains a sequence of nucleotides. Although there are only four different nucleotides, the combination and amount present are endless. This endless combination of nucleotides is what gives genes their variability. As previously mentioned, each chromosome or gene comes in pairs. Organisms receive one gene from their mother and the other from their father. Because each gene has two pair coming from two parents, there are basically four outcomes that could surface for any one trait. There is no known way to pinpoint exactly what traits an offspring will have, but there are ways to determine the probability of an offspring having a certain trait. A Punnett square is used to determine this probability. A square is used to cross certain genes to determine the probability of an offspring having the traits associated with those genes. In a Punnett square, genes are represented by alphabets. A capital letter means the trait is dominant (shows up in some way no matter what) and a lower case letter means the trait is recessive (will show diminished signs if it shows up at all, there must be two recessive genes present in order to completely see the recessive trait). |
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