Genetics & Medical Terminology

Genetics – Chromosomes – Trisomy – Prenatal screening – Diagnosis

Links to Information about Chromosomes and Trisomy
&
Glossary of Genetics and Medical Terms

The  U.S. National Library of Medicine   (NLM), maintained by the  National Institutes of Health is the world’s largest medical library.   It contains a great deal of information regarding chromosomes and chromosome disorders.   This is public domain information and, as such, may be freely distributed and copied, but NLM requests that, in any subsequent use, the NLM be given appropriate acknowledgement.

~ A series of links to NLM information about genetics, chromosomes, trisomy, prenatal screening and diagnosis is provided below: ~

An excellent glossary of genetics and medical terms can be found at the NLM’s “Genetics Home Reference” system.   Click here to access it:   http://ghr.nlm.nih.gov/glossary

A Genetics Home Reference, a guide to understanding genetic conditions, can be found here:   http://ghr.nlm.nih.gov/

What is a chromosome?   Click this link to read an explanation about chromosomes and their functions:  http://ghr.nlm.nih.gov/handbook/basics/chromosome

NLM’s Genetic Home Reference provides information about each of the 23 pairs of chromosomes.   Click here to access this information:  http://ghr.nlm.nih.gov/chromosomes

Information about chromosome 18 and trisomy 18 (Edwards syndrome).  Humans normally have 46 chromosomes in each cell, divided into 23 pairs. Two copies of chromosome 18, one copy inherited from each parent, form one of the pairs. Chromosome 18 spans about 76 million DNA building blocks (base pairs) and represents approximately 2.7 percent of the total DNA in cells.   Trisomy 18 occurs when each cell in the body has three copies of chromosome 18 instead of the usual two copies. (The word “trisomy” comes from “tri,” the Greek word for “three.”) In some cases, the extra copy of chromosome 18 is present in only some of the body’s cells. This condition is known as mosaic trisomy 18.   Tetrasomy is a less common disorder.   More information can be found by clicking on the following two links:

http://ghr.nlm.nih.gov/chromosome/18

http://ghr.nlm.nih.gov/condition/trisomy-18

Information about chromosome 13 and trisomy 13 (Patau syndrome).  Humans normally have 46 chromosomes in each cell, divided into 23 pairs. Two copies of chromosome 13, one copy inherited from each parent, form one of the pairs. Chromosome 13 is made up of about 114 million DNA building blocks (base pairs) and represents between 3.5 percent and 4 percent of the total DNA in cells.   Trisomy 13 occurs when each cell in the body has three copies of chromosome 13 instead of the usual two copies. (The word “trisomy” comes from “tri,” the Greek word for “three.”) In some cases, the extra copy of chromosome 13 is present in only some of the body’s cells. This condition is known as mosaic trisomy 13.   Tetrasomy is a less common disorder.  More information can be found by clicking on these two links:

http://ghr.nlm.nih.gov/chromosome/13

http://ghr.nlm.nih.gov/condition/trisomy-13

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