The Meaning of Genotype and Phenotype and the Effect of the Coursework

The Meaning of Genotype and Phenotype and the Effect of the Environment on the Phenotype of an Organism - Coursework Example    The CFTR gene which for encodes a protein that transports chloride ions across cell membranes has two genes. The dominant gene (A), which is the normal version of the gene. The recessive gene (a), which is the mutated version of the gene. Those with cystic fibrosis receive both the recessive alleles. The genotype of individuals is then (a, a). While the phenotype of the recessive genotype, is the absence of protein that transports chloride ions, and so, cystic fibrosis. The phenotype is not only expressed by the effects of the phenotype alone. The environmental condition also affects the expression of phenotype. The effect of the environment on the phenotype of an organism is best understood through an experiment. Taking two samples of the colors plant, both samples originate from the same plant. The samples are grown in two separate chambers. The environmental condition varied is the amount of light delivered. All other factors are kept constant in both samples. Though both sam ples have similar genotypes, the growth of both samples varies. The sample that receives higher proportion of light compared to the other grows faster and thrives. While the sample that receives lesser light compared to the other, has stunted growth and is weak. The environmental condition has affected the phenotype irrespective of the genotype being common to both samples. Explain how DNA replicates itself. (200 words) DNA replication is based on the model presented by Watson and Crick. The model suggests semi-conservative replication of DNA strands. This replication is called so, because a half of the strand is conserved while the other half is newly formed. DNA replication occurs in the nucleolus of the nucleolus.DNA replication takes place in the interphase of the cell cycle. In order for DNA replication to take place, the DNA strands must first be separated. The DNA strands are separated by the enzymatic action of an enzyme. The enzyme breaks the hydrogen bonds present between the complementary base pairs. The two DNA strands are separated. The four bases involved in DNA replication are adenine, thymine, cytosine and guanine. Nucleotides when paired with an additional phosphate become activated nucleotides. The activated nucleotides are capable of pairing up with their complementary base pairs with the help of enzyme DNA polymerase. The activated nucleotides form bonds with their complementary base pairs. DNA polymerase links the sugar and innermost phosphate groups of adjacent nucleotides together. The extra phosphate ions are released. This marks the replication of DNA from a single DNA molecule; both new DNA molecules conserve a single strand of the old DNA molecule. Explain the type of mutation that resulted in the sickle cell anaemia. (200 words) Mutation is the change in genetic material of an organism as results of base deletion, base substitution or base addition. The change in genetic material causes a different allele of a gene to be expressed, which in turn causes different phenotypic characteristic. Sickle cell anaemia is an inherited blood disorder that causes a change in haemoglobin characteristic. Haemoglobin is composed of four polypeptide chains. That is two alpha chains and two beta chains. The normal coding for haemoglobin in the beta chains is; Val-His-Leu-Thr-Pro-Glu-Glu-Lys-. These coding codes for normal hemoglobin. However, a base substitution, causes the normal base sequence CTT to be expressed as CAT.