Chromosomes and Heredity essays

Chromosomes and Heredity essays The theory of the genetic basis of heredity was quite unheard of until the time of Gregor Mendel who proved with his experiments on pea plants that organisms inherited their traits from their parents. It was Mendel who first proposed that genes were the basic units of all living organisms. Children receive half their chromosomes from their father and half from their mother and hence they share the character traits of their parents. Each human being has two complete sets of 23 chromosomes, which are responsible for controlling all the bodily functions. Each parent in effect contributes one complete set of the 23 chromosomes to the child. Genetic information is stored inside the chromosomes in the forms of DNA strands and there are around 40,000 genes, which are responsible for instructing the ribosomes to synthesis specific proteins. (for specific functions). A particular gene is responsible for a particular character trait and parents pass on genes to their children, which is the fundamental principle behind inheritance. Furthermore every gene may have two or more different forms known as alleles. The genetic makeup of a person called the genotype is actually the combination of these inherited alleles. A person may either have homozygous alleles or heterozygous alleles. Alleles for a particular trait may either be dominant or recessive. The phenotype (physical appearance) of the person is determined by the expression of the dominant alleles. There are some cases where neither of the alleles are totally dominant in which case the phenotype is a combination of the phenotypes of both the alleles. So we see that the phenotype or the ultimate physical trait of a person is directly dependent upon the genetic information received from the parents. ...