Heredity, Genetics and Protein Synthesis Essay Example | Topics and Well Written Essays - 3500 words

Heredity, Genetics and Protein Synthesis - Essay Example In ancient times, people wondered how babies were born and why they share many characteristics of their parents. For long it was a mystery, until Gregor Mandel, an Austrian monk introduced some principles that formed the basis of modern genetics. He explained that these characteristics or heritable properties are transferred as units called genes. (Sharma 2005, p.2). With the development in science and availability of modern research techniques, it was soon confirmed that these genes are nucleotide sequence in a DNA molecule. This sequence is like an instruction manual of how characteristics will be developed in an individual. As Mandel had explained earlier, one characteristic or gene is inherited from each parent. But where are these genes located and how they are transferred from parents to offspring? This was the question that was soon answered following a year after Mandel’s death. It was initially proposed that genetic material is located in nucleus. Walter Sutton and Th eodore Boveri proposed in 1903, that genes are carried in special structures called chromosomes. (Sharma 2005, p.14). Genes are set of instruction carried by special molecules called Deoxyribonucleac Acid or DNA. It is this molecule that winds around histone proteins to form a chromosome. DNA has a unique structure that enables it to preserve and transfer genetic material. DNA is a double stranded, anti parallel helical structure with a deoxyribose sugar and a phosphate backbone. Each nucleotide has either a purine or pyramidine nitrogenous base attached to it. Guacine pairs with cytosine and thymine pairs with adenine on complementary strands. This variable sequence of base pair is actually the genetic code. A specific gene is present at fixed location on a chromosome called locus. There are 23 pairs of chromosome present in a somatic cell of a human being and each parent contributes one chromosome to form that pair. How these chromosomes are transferred from parents to offspring? The answer is simple; gametes of each parent contain 23 chromosomes and when two gametes fuse these chromosomes are added together in one cell called zygote. All the subsequent cells that are formed from zygote by the process of mitosis contain identical genetic material. So any somatic cell has a pair of same chromosome, one from mother and one from father. As mentioned earlier, genes are present at fixed locations on a chromosome. If there is a pair of chromosome it means there will be two sets of same gene, one from each parent present at the same loci. The base sequence of these two sets of genes may not be same and this variation in gene is called an allele. (Kail & Cavanaugh 2007, p.44). Now important question is which of these two genes will be expressed in the offspring? Remember that genetic makeup of an individual is called genotype and its physical expression is a phenotype. In most cases, both alleles are expressed to produce a phenotype. Sickle cell disease is caused by mutation in the beta haemoglobin gene. When this gene is expressed it forms an abnormal protein which causes alteration in the shape of red blood cell from biconcave disk to sickle shaped (Bloom, 1995). As part of previous discussion, this gene also has two alleles inherited from each parent. An individual with only one mutated gene will not get this disease because the other normal gene will also be expressed and compensate for abnormal gene. This is a very good example of how genes are key determinants of human characteristics. Not all sequences in a DNA represent a gene. All the genetic material in nucleus and in mitochondria together is called a genome. Only 1% f this genome is actually genes. Thousand of these genes guide species in growth and development of other characteristics. One gene