Any modification that interferes with the number or structure of chromosomes in a cell is called a chromosomal mutation. Chromosomal mutations can be classified into numerical mutations, where there is change in the number of cell chromosomes, and structural mutations, where there is change in the shape or size of one or more cell chromosomes.
Numerical mutations are further subdivided into aneuploidies and euploidies. In aneuploidies, there is an increase or loss of one or more chromosomes; In euploidies, the increase or loss will be in complete chromosomal batches, also known as genomes.
The development and function of an organism is in large part controlled by genes. Mutations can lead to changes in the structure of an encoded protein or to a decrease or complete loss in its expression. Because a change in the DNA sequence affects all copies of the encoded protein, mutations can be particularly damaging to a cell or organism. In contrast, any alterations in the sequences of RNA or protein molecules that occur during their synthesis are less serious because many copies of each RNA and protein are synthesized.
Geneticists often distinguish between the genotype and phenotype of an organism. Strictly speaking, the entire set of genes carried by an individual is its genotype, whereas the function and physical appearance of an individual is referred to as its phenotype. However, the two terms commonly are used in a more restricted sense: genotype usually denotes whether an individual carries mutations in a single gene (or a small number of genes), and phenotype denotes the physical and functional consequences of that genotype.
The kidney is referred to as an excretory organ because it excretes nitrogenous wastes. It is also a major homeostatic organ because it maintains the electrolyte Acid-Base, and fluid balance of the blood.
