Mendel's Law of Heredity
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In simpler terms Genetics is the study of inheritance. This principle of inheritance was put forward by Gregor Mendel in the early 1800s. Mendel studied the traits of several plants from the church compound he used to work as a monk. By being a monk gave him much time to handle and deal with the plants that were growing in the church compound especially in the flower gardens. These experiments included the study of several traits from these plants which included the peas and the flowers in the farm or the flower garden nearby. The traits that Mendel studied included issues like the color of the flower, shape and color of the pods of the peas, length of the stem of the plant, the color and shape of the seeds and the location of the flowers onto the plant itself.
Gregor Mendel was crowned father of genetics after carrying out experiments on garden peas in the garden of monastery where he was a monk between the years 1822-1884. He used pure breeds organisms (garden peas) that when allowed to self pollinate several times produce young ones that look similar to their parents. (Bateson, 1909). Living organisms transmit genes in a process known as heredity. Genetics studies the genes that are made up of the DNA that is embedded in threadlike structures in the nucleus of each cell called chromosomes. Genes are packages in which traits are carried on from one generation to another. Traits are characteristics of an organism. When physically expressed traits are known as the phenotype of the organism. (Edelson, 1999). Each individual has a unique combination of alleles called a genotype. These are internal genetic traits.
The issues underlying the whole issue of Heredity circulates around a number of definitions of terms. The terms related to the Mendelian law of heredity are as follows: Allele which is the form in which one or more forms of a gene may for example short and tall. A living organism like Man can either be tall or short. Dominant Allele is an allele that overpowers a second form of the same gene. If tall empowers short then the organism would turn out to be tall in real life and vice versa. Gamete is basically a reproductive cell. These could be either from the female or the male organism in the fertilization process.
Genes are packages in which traits are passed on from one generation to another. Each trait is contained in a specific gene. Genes always occur in pairs, called allelic pairs, which provide alternative forms of the same gene, for example, dwarf and tall alleles for the height gene. Genes are located in threadlike structures in the nucleus of each cell called chromosomes. During reproduction cell division takes place producing gamete (egg cells and sperm cells) in a process known as meiosis (Griffiths et al., 2000). During meiosis chromosomes divide where a single chromosome of each pair goes to each of the two gametes resulting to each gamete having half the number of chromosomes. During fertilization, the gametes come together, that is, the egg cell joins with the sperm cell producing a full complement of the chromosomes. For example, human being’s gametes add to twenty three chromosomes after fertilization. Each parent donates one of their genes for every trait.
Heterozygous is a condition whereby two alleles express themselves together in equal frequency and power. The allele for tall may exist together with that of shortness creating an individual with an average height. Homozygous is the exact opposite of heterozygosis. In this case, the two alleles are the same as opposed to heterozygous where the alleles are very different. When two alleles of tallness exist together then the individual will be extremely tall and the same to the case when short co exists with another short allele in the same individual. This person will be very short as compared to the rest.Recessive refers to an allele that is concealed in offspring by an allele that is dominant in this pair. Genes are the basic units in which characteristics of individuals are passed from one generation to another. For instance, a plant with white flowers must carry the gene for the same characteristic and the same to a plant with white flowers. This gene is expressed in two forms called the alleles (Chial, 2008).
Sex cells simply divide into two equal halves called gametes. The gamete from the male fertilizes that of the female to produce a very fertile egg. This fertilized egg is simply called a zygote. The zygote in most cases will contain the genetic information from both the parents. A zygote may contain two different alleles for example the allele for white flower and that for red flower and this is called heterozygous. On the contrary, a zygote may contain alleles of the same characteristic and thus will automatically bear that same trait (Bizzo & El-Hani, 2009).