Basic Genetics

What is DNA?

DNA is the very extensive instruction manual for creating a human being. Our DNA is found in nearly all the cells in our body. Everyone’s DNA is a little different. These differences are what make us all unique and special. Scientifically, DNA stands for Deoxyribonucleic Acid. All DNA instructions are written in 4 easy letters, A (Adenine), C (Cytosine), G (Guanine), and T (Thymine). These letters make up the language that tells our cells how to work.

http://www.biologycorner.com/bio1/DNA.html http://www2.le.ac.uk/departments/genetics/vgec/highereducation/topics/cellcycle-mitosis-meiosis

What are Chromosomes?

All of our DNA is normally organized into 46 chromosomes. Chromosomes are kind of like books. We get a set of 23 books or chromosomes from our mothers, and a set of 23 from our fathers. Each of these sets of books are labeled with names “1” through “22”, and the last book is our sex chromosome. Sex chromosomes are what tell our bodies to be a boy or a girl. A girl will have two “X” books (one from mom and one from dad), and a boy will have an “X” (from mom) and a “Y” (from dad). Individual chromosomes kind of look like a bow tie. One side of the bow tie is usually shorter and is call the “P” arm – which stands for “Petite”. The other half of the bow tie is usually longer and is called the “Q” arm. The knot in the middle is called the “centromere”. The centromere helps the chromosomes pair together with their partners when the cell wants to grow and make more cells.

http://staff.jccc.net/pdecell/celldivision/chromoterm.html

http://www.treachercollins.co.uk/gene/chrom.htm

What are Genes?

All chromosomes or books have chapters in them, and these are what we call genes. Genes give instructions on how to make the proteins in our body. Without these genes, we are unable to make the proteins properly. What is really cool, is that everyone has about 20,000 to 25,000 genes in their DNA! Although every cell has all our DNA, genes are able to be turned on and off. This is what helps give us all types of different cells, like blood cells, skin cells, brain cells, and hair cells etc. Sometimes genes could be missing or we could have more than two copies of genes. This loss, or extra DNA can lead to changes in the way our bodies develop and grow.

http://www.biologycorner.com/bio1/celldivision-chromosomes.html

What does 2q23.1 deletion/duplication mean?

The number letter combination tells us a description of where the change in our DNA has taken place. A deletion means that there is DNA missing. A duplication means that there are extra copies of DNA. 2q23.1 can be broken down. The first 2, means that the change occurred in chromosome number “2”. The letter “q” means that the change happened on the long arm of the chromosome. The next group of numbers, tells us that the change happened in the 23.1 section of the “q” arm. If you have a specific result that gives a range, for example, 2q23.1-2q23.3, that means that there has either been a loss of that entire area, or that the stretch of DNA has more than two copies. The MBD5 gene is found in the 2q23.1 region of the chromosome.

What does the MBD5 gene mean?

MBD5 is an abbreviation for methyl binding domain 5. MBD5 is a name given to the gene that is either missing or duplicated in children with 2q23.1 deletion/duplication disorders. This is the ONLY gene that is seen in EVERY child that has the disorder. It is said to be the “CAUSAL” gene or the one that causes someone to have the disorder.