chromosomes the haridity carrier
When a cell is not divided, there is not much detailed structure to be seen in nucleus, even if it is treated with special dyes called stains’ But just after one cell division, a number of log thread-like structures appear in nucleus and show up very clearly when the nucleus is stained The thread-like structure is called chromosomes Why can these chromosomes not be seen well in the cell which is not divided? It is because they become long and thin like fine pieces of thread The scientists’ observations show that each chromosome has another chromosome Scientists have also found that in all cells, both animal and plant, the chromosomes are in pars Two chromosomes belonging to a pair look exactly alike and we call them homologous chromosomes Homologous in Greek means “agreeing” Each chromosome is seen to be made up of two parallel strands called ‘chromatides’. When the nucleus is divided into one chromatid, from each chromosome goes into each daughter nucleus The chromatid each nucleus now becomes chromosome and then they make themselves ready for the next cell division The process of duplicate copying is called ‘replication as each chromosome makes a replica, an exact copy of itself Function of Chromosomes Along the length of chromosomes, is a series of chemical structures called ‘Genes’ The chemical which forms genes is called DNA (Deoxyribonucleic Acid). Each gene controls some parts of chemistry of a cell There will be a gene on one chromosome, which causes the cells of stomach to make the enzyme “Pepsin We know chromosome replicates (make gene by gene) When chromatids separate at mitosis then in that case each cell will receive a full set of genes. In this way, chemical Instructions in zygote are passed to all cells of body Therefore, all chromosomes, genes and instructions are reproduced by mitosis and are passed on to complete the entire cell gene, because brown eye does not affect in stomach and making pepsin gene which does nol function the cell of eye There is a fixed number of chromosomes in each species, man’s body cell contains 46 chromosomes, mouse cell contains 40and garden pear cell contains 14 chromosomes The number of chromosomes in species is same in all its body cells The chromosomes have different shapes and sizes and can be recognized by a Lrained observer Il is always in pau, two long, two short and two medium one This is because when zygote is formed, one of each pair comes from the male’s gamete (sex cell) and one from female gamete Our 46 chromosomes contain 23 from mother’s side and 23 from father’s side The number of chromosomes in each body cell, plant or animal is called “Diploid number” Because, we know that they are in pair and in an even number always The genes on chromosomes carry the instructions, which turn a single cell zygote into a bird or a rabbit. The zygote is formed at fertilization when a male gamete fuses with female gamete Each gamete bnngs a set chromosomes to the zygote The gamete contains only half diplod numbers of chromosomes, otherwise, their number would double each time, an organism reproduced sexually Each human female ovum has 23 chromosomes When sperm and ovum fuse at fertilization, the diploid number 46 (23 +23), chromosomes are produced.