Gamete – A vehicle of inheritance: Your life has started as a single cell _ the zygote. All the cells of your body arose from it through mitosis. It was not just an ordinary cell; rather it was the pioneer representative of your identity. Its nucleus had a complete programmer of coded genetics information for your developing into a unique individual.
Each cell of your body descended from it, has received the same set of genes. The development of your entire personality at all stages of your life; from embryo through baby, child hood, youth to old age is under the direction and control of this complete set of genes _ our very personal genome.
How was your zygote formed? Yes! It was formed by the fertilization of your paternal and maternal gametes. Those two tiny cells _ a sperm and an egg provided the only possible physical link between you and your parents. Anything to be transmitted between generations must pass through this genetic bridge. But how? Nucleus is the master _ organelle of every cell. It controls all activities of cell. The most significant structures in the nucleus are chromosomes. They were discovered by waldeyer in 1876.
Organisms have number of chromosomes specific to their species
Each kind of organism has a specific number of chromosomes. This number remains constant in all individuals of a species generation after generation. The nucleus of your zygote and each somatic cell of your body that arose from it contain 46 chromosomes. It is the diploid (2n) no. of our species homo sapiens. Similarly frog’s species constant number is 26; and for garden pea it is 14.
These chromosomes are in the form of pairs. Two chromosomes, which are similar in their shape, size and position of centromere, make one homologus pair. So your 46 chromosomes are actually 23 pairs of homologous chromosomes. Each member of a homologus pair is called a homologue.
One homologue of each pair comes from father’ the other homologue comes from mother. Thus every cell of your body contains two sets of 23 chromosomes each. One haploid set (n=23) is paternal is origin, which has been contributed by the sperm nucleus, while the other haploid se (n=23) is maternal which has come from the egg nucleus. These two sets of chromosomes have provided the physical basis of your heredity.