Overview of Chromosome Abnormalities

What is a chromosome?

The human body is made up of cells. For example, when you have a sunburn, your skin peels, and you are shedding skin "cells." In the center of each cell is an area called the nucleus. Human chromosomes are located in the nucleus of the cell. A chromosome is a structure in the nucleus that contains your genes. Your genes determine your traits, such as eye color and blood type.

Anatomy of a cell

How are chromosomes inherited?

The usual number of chromosomes in each cell of your body is 46 total chromosomes, or 23 pairs. You inherit half of your chromosomes (one member of each pair) from your biological mother, and the other half (the matching member of each pair) from your biological father.

Scientists have numbered the chromosome pairs from 1 to 22, with the 23rd pair labeled as X's or Y's, depending on the structure. The first 22 pairs of chromosomes are called "autosomes." The 23rd pair of chromosomes are known as the "sex chromosomes," because they determine whether someone will be born male or female. Females have two "X" chromosomes, and males have one "X" and one "Y" chromosome. A picture of all 46 chromosomes, in their pairs, is called a karyotype. A normal female karyotype is written 46, XX, and a normal male karyotype is written 46, XY.

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Raymond Lewandowski, MD
Medical Director, Geneticist

Ofelia Rivera
Office Manager

Deborah Dansby
Sonographer Supervisor

Denise Dominguez
Valley Supervisor

Andrea Ramirez
Senior Genetic Counselor

CPSST - Driscoll Genetics Services
5920 Saratoga Blvd. 540
Corpus Christi, Texas 78414
Phone: (361) 694-1600 or (361) 985-6600
Fax: (361) 985-6603
Hours 8-5 pm

CPSST - Driscoll Genetics Services -Brownsville
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Brownsville, TX 78520
Phone: (956) 544-5663
Fax: (956) 544-7386

CPSST - Driscoll Genetics Services - Harlingen
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Harlingen, TX 78550
Phone: (956) 428-0897
Fax: (956) 428-0899

CPSST - Driscoll Genetics Services - McAllen
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McAllen, TX 78501
Phone: (956) 686-0503
Fax: (956) 668-0503
Hours: 8 – 5 Monday – Friday

Further Reading

Genetics Information Index

Overview of Birth Defects

Chromosome Abnormalities

Single Gene Defects

The Difference Between a Chromosome Abnormality and a Single Gene Defect

Multifactorial Inheritance

Teratogens

Non-Traditional Inheritance

Evaluating a Child for Birth Defects

Testing for Birth Defects

Uses of Genetic Testing

Genetic Services: When, Where, How

Identification, Treatment, and Prevention of Birth Defects

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