Just as genes come in pairs, chromosomes also come in pairs. Each cell in our body has 23 pairs of chromosomes (for a total of 46); one member of each pair is inherited from the mother and the other is inherited from the father. The first 22 pairs (numbered 1 through 22) are called autosomes and they determine most of our features. The last pair is called the sex chromosomes and they determine if we are male or female. Females have two X chromosomes and males have one X chromosome and one Y chromosome.

It is possible to tell the chromosomes apart by their size and their "banding pattern." The banding pattern is a result of a chemical staining process used in the laboratory to help researchers see the chromosomes more easily. Each chromosome is divided into two sections or "arms." The short arm is called the "p" arm and the long arm is called the "q" arm. The bands on each arm are numbered. When researchers study the chromosomes (a process called chromosome analysis) they try to determine if there are any missing or extra pieces of the chromosomes.

• Candidate Genes
• Exploring Chromosome 2
• Exploring Chromosome 3
• Exploring Chromosome 7
• Exploring Chromosome 15
• Searching Chromosome X

HOW GENES ARE NAMED
You may wonder how genes are named. As you may have guessed, some names are abbreviations for the full gene names. Other genes are named after similar genes in other organisms. More ...

HOW CHROMOSOME ABNORMALITIES HELP US FIND GENES
Genetic researchers use many different tools and strategies to look at the genetic material (DNA) inside our cells to find the exact gene(s) that cause a genetic disorder such as autism. More ...

HOW GENOME SCREENS HELP US FIND GENES
In order to determine the genes that may be involved, scientists also perform what are referred to as "genome screens." To do this they use maps of the chromosomes in order to look for genes. More ...