Chromosomes' Function

Genetics is the branch of biology that studies heredity and the variations in organisms. Chromosomes, the threadlike structures made of a combination of DNA and protein, found in the nuclei of cells, form one of the most integral units of study under genetics. In humans, each cell contains 23 pairs of chromosomes, one of each pair taken from each parent. Of these 23 pairs, 22 pairs, or 44 chromosomes, are non-sex chromosomes, also known as autosomes, and a single pair makes up a sex chromosome. In females, the sex chromosome is made up of a double X sequence, whereas male sex chromosomes are made up of an XY sequence. This forms the most basic difference between males and females at the cellular level. Chromosomes in humans function as units that contain genes, the controllers of heredity. To understand the various ways in which chromosomes function, read on.

Basic Function of Chromosomes
In the broadest sense, chromosomes function is to control all the activities of a living cell. Chromosomes are essential for the process of cell division and are responsible for the replication, division and creation of daughter cells, that contain correct sequences of DNA and proteins. Proteins make up one of the most important components of the human body, they are responsible for building muscles and tissues, growth and repair, as well as the synthesis of the thousands of enzymes like DNA replication enzymes, produced by the body. Protein synthesis steps, and their successful completion is the responsibility of genes, that are contained in chromosomes. Chromosome functions include holding genes, the units of heredity.

Genes are located at a particular point on a chromosome, known as its locus. Each chromosome contains DNA in a double helix structure, which houses thousands of genes along the strand, each with their own loci. Genes are the units that hold codes that control the building and maintenance of cells; they also control the characteristic traits that are passed on from parents to offspring.

Chromosomes are often referred to as the 'packaging material' that hold DNA and proteins together in eukaryotic cells (cells that have a nucleus). Cell division is a continuous process that must occur for an organism to function, whether for growth, repair or reproduction. During cell division stages, it is the chromosome that is responsible for the replication and distribution of DNA amongst new cells. Strangely enough, the function of chromosomes in plant cells are the same as the function of chromosomes in animal cells. In fact, chromosomes differ structurally more between prokaryotes and eukaryotes, as opposed to different species.

Structure of Chromosomes
In prokaryotes, or cells that do not contain a nucleus, like bacteria, the chromosome is generally circular in structure. In place of a nucleus, prokaryotes contain what is referred to as a nucleoid which contains the DNA. In eukaryotes, or cells that contain a nucleus, the chromosome is linear in structure. Chromosomes can exist in duplicated or unduplicated stages. When unduplicated, the chromosome appears as a single strand, whereas duplicated chromosomes consist of two strands, which are linked by a centomere. Each of the two strands make up sister chromatids. Duplicated chromosomes have a typical structure, likened to an asymmetrical version of the letter X, with the two chromatids intersecting at the centomere. Typically, one arm is longer than the other.

Chromosomal Abnormalities and Gene Mutation
Although DNA replications are mostly accurate, there are times when errors in replication occur, owing to alterations in the base gene sequence. These errors give rise to what is known as mutations. Changes in the chromosomal content of a cell, including errors in replication, DNA and gene mutations can give rise to a number of medical conditions, like Down Syndrome. This does not mean however, that all chromosomal abnormalities will give rise to a disease, though a parent with chromosomal abnormalities has higher chances of a giving birth to a child with genetic disorders. There is hope though, with advances in genetic engineering, for people with such conditions.

Chromosomes function as the very basis of life and its continuity. Chromosomes and genes are just the tip of the iceberg under the fascinating subject of genetics. The leaps and bounds made by advances in technology will, I hope, help genetic research find cures for the diseases that plague the world.