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The human genome is often referred to as a "blueprint" and contains all
of the information and instructions necessary for defining a human being.
The term genome refers collectively to the DNA and associated protein
molecules contained in an organism or a cell. The human genome consists
of 23 pairs of chromosomes threadlike packages of genes and other
DNA with each parent contributing one chromosome to each pair. A gene is a specific sequence of DNA and is actually the functional
unit of inheritance. Most genes contain the information needed to make
a protein, or molecules that carry out all of a cell's vital activities.
Therefore, slight variations in genes lead to slight changes in a protein.
Although some human diseases are explained by alterations in a single
gene or of a single chromosome, most are complex and may involve
multiple genes and protein pathways. A myriad of genes, as well as environmental factors, are believed
to control the complex and integrated processes necessary for fetal
development. When one or more of these processes goes awry, it can
result in the birth of an individual with a genetic alteration.
Scientific studies, often those that use other organisms as a model, will provide information about biological and
regulatory processes involved in human development and will identify
critical pathways in which genetic changes result in disease. This
information will come not only from human studies, but also from other
model organisms such as mouse or yeast that can provide insights into
how key genes operate in complex systems.![top link](https://webarchive.library.unt.edu/eot2008/20090831021041im_/http://www.ncbi.nlm.nih.gov/books/bookres.fcgi/system_default/top.gif)
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The number of babies that die in the first 28 days of life (neonates) and during the first year of life (infants) has fallen dramatically over the last 50 years. |
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