All About Chromosomes

Every human being has tiny structures inside their cells called chromosomes. The chromosomes are made from DNA and protein, and the information inside the chromosomes are like a recipe that tell the cells of the body how to function and replicate. All forms of life have unique sets of instructions with the 'recipes' for their life. The chromosomes of a human describe their eye color, height, type of nose, and much more, including whether a person will be a male or female. The word 'chromosome' comes from the Greek words 'chroma', meaning color, and 'soma', meaning body.

The chromosomes are found in the nucleus of every cell and the different organisms of the world have different numbers of chromosomes. Humans have 23 pairs of chromosomes for a total of 46 chromosomes in each cell. Twenty-three of the chromosomes come from the father and the other twenty-three come from the mother. The cells of a goldfish have 100, and a dog has 78, a horse has 64, a rabbit has 44, and a fruit fly has 8. Even a garden pea cell has 14 chromosomes.

The chromosomes cannot be seen with the naked eye or a microscope. They are small and thin, but when a cell gets ready to divide, the chromosomes become densely packed and wound together, and it is at this time a scientist can see the chromosomes. They can be found in pairs and appear as short little worms. Some chromosomes may be longer because they contain more DNA.

The interphase of the cell cycle occurs when the cell is not dividing, and the chromosome is in its chromatin form. In this form, the chromosome is a long and very thin strand. When the cell begins to divide, that strand replicates itself and winds up into shorter tubes. Before the split, the two tubes are pinched together at a point called the centromere. The shorter arms of the tubes are called the 'p arms' and the longer arms are called the 'q arms.'

All the chromosomes carry different types of information. One chromosome may contain information about eye color and height. There is another chromosome that determines the sex of a person. Another chromosome may determine blood type, hair color, skin color, and other characteristics of a human. A plant chromosome may contain information about the shape of a leaf.

Inside each chromosome, there are specific sections of DNA called genes. Each gene contains the special code or recipe to make a specific protein. The proteins determine how a human grows and what traits will be inherited from parents. Not all traits will be inherited from a parent. For example, the specific sequence of a gene is called an allele. One person may have an allele for brown hair and another person may have one for blonde hair. The gene is sometimes called a unit of heredity. Humans have about 30,000 genes in their 46 chromosomes.

Some organisms have many more chromosomes than humans but often they include blank DNA which is called junk DNA. Nearly every cell in the human body carries a complete set of chromosomes which means a single cell in a body contains all the information and instructions for a human.

In summary, chromosomes include the 'recipe' for life. They are the unique instructions for all living things from humans to plants to a single-celled organism. The chromosomes of a human include 46 pairs, 23 received from the father and the other 23 from the mother.