Chromosome how many

For instance, some proteins such as keratin, which is found in hair and nails, are structural. Other proteins may serve as enzymes — molecules that help certain chemical reactions in the body.

Yet others can play a role in passing messages from one cell to another cell signalling molecules or in protecting humans against disease e.

In scientists around the world announced the results of an immense collaborative scientific effort, the final sequencing of the entire human genome — a sequence of around 3 billion base pairs.

This was a scientific breakthrough of immense importance. Thanks to these volunteers, scientists now understand more about human genetic information, genes — a field of study called genomics. Eventually, further genomic studies should help scientists to develop better diagnostic tools and treatments.

Studying the genetic sequence of different individuals allows scientists to work out which genes are responsible for how our cells work or which genes are associated with particular human features — such as some medical conditions and how people might respond to medicines. For instance, some individuals may have an abnormality in their genetic sequence resulting in a particular medical condition. Such conditions are called genetic disorders, examples of which are the blood disorders sickle cell disease and thalassemia.

Other medical conditions, such as type II diabetes, might be associated with particular genes or genetic sequences. Click Image to Enlarge. The usual number of chromosomes inside every cell of your body is 46 total chromosomes, or 23 pairs. You inherit half of your chromosomes from your biological mother, and the other half from your biological father. Scientists have numbered the chromosome pairs from 1 to 22, with the 23rd pair labeled as X or Y, depending on the structure.

The first 22 pairs of chromosomes are called autosomes. Chromosomes are thread-like molecules that carry hereditary information for everything from height to eye color.

They are made of protein and one molecule of DNA, which contains an organism's genetic instructions, passed down from parents. In humans, animals, and plants, most chromosomes are arranged in pairs within the nucleus of a cell. Humans have 22 of these chromosome pairs, called autosomes. Humans have an additional pair of sex chromosomes for a total of 46 chromosomes. The sex chromosomes are referred to as X and Y, and their combination determines a person's sex. Typically, human females have two X chromosomes while males possess an XY pairing.

This XY sex-determination system is found in most mammals as well as some reptiles and plants. Whether a person has XX or XY chromosomes is determined when a sperm fertilizes an egg. Unlike the body's other cells, the cells in the egg and sperm — called gametes or sex cells — possess only one chromosome. Gametes are produced by meiosis cell division, which results in the divided cells having half the number of chromosomes as the parent, or progenitor, cells. In the case of humans, this means that parent cells have two chromosomes and gametes have one.

All of the gametes in the mother's eggs possess X chromosomes. The father's sperm contains about half X and half Y chromosomes. The sperm are the variable factor in determining the sex of the baby. If the sperm carries an X chromosome, it will combine with the egg's X chromosome to form a female zygote. If the sperm carries a Y chromosome , it will result in a male.