DHREAMS - Diaphragmatic Hernia Research & Exploration Advancing Molecular Science
About CDH
CDH

Genetic Overview


What are Chromosomes?
What are Genes?
What is DNA?
What are Biological Samples?
What is a Genetic Analysis?
Genetic Analogy


What are Chromosomes?

Our bodies are composed of millions of cells.  Within the center of each cell are rod-like structures known as chromosomes.  Typically, there are 46 chromosomes in each cell.  They are grouped into 23 pairs, one member of each pair coming from our mother and the other from our father at the time of conception.  The first 22 pairs of chromsomes are the same in both men and women and are number 1 through 22. The last two determine our sex and are call X and Y.  Women have two X chromosomes and men have one X chromosome and one Y chromosome.


What are Genes?

Our chromosomes carry our genes, the basic units of heredity. Our genes are made up of DNA. There are approximately 30,000 genes that influence our growth and development.  Each gene occupies a specific location on a chromosome.  With the exception of the X and Y chromosomes, there are two copies of each chromosome and therefore two copies of each gene. When a mistake or an alteration occurs in one or more of our genes our body does not develop properly, and this can lead to a genetic disease.


What is DNA?

Our genes are composed of DNA and DNA is made up of four chemical bases which are represented by letters: adenine (A), guanine (G), cytosine (C), and thymine (T). These base are strung together in pairs (base pairs) in specific combinations and lengths to spell our genes.  When the base pair sequence is altered, our DNA code is altered, and this can lead to a genetic disease. 

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What are Biological Samples?

The complete set of our genes are present in nearly every cell of our body.  A blood sample is the most common type of biological sample that is used for a genetic analysis, but saliva samples, amniotic fluid, skin samples, and other tissue samples can also be used for a genetic analysis.  Sometimes it is important to study multiple tissue types from one individual as the genetic information in one tissue type may be different from the genetic information in another tissue type.


What is a Genetic Analysis?

A chromosome analysis or karyotype is the most basic genetic analysis.  A chromosome analysis is able to detect missing or extra chromosomes or other large chromosome abnormalities but cannot detect small chromosome abnormalities or single gene abnormalities.  The genetic analysis performed as part of our research study is a DNA microarray.  A DNA microarray is  anextremely sensitive and sophisticated analyses that is able to detect small deletions or duplications of DNA that cannot be detected by a chromosome analysis.  Analysis of specific genes or gene sequencing will also be performed. 


Genetic Analogy

 

Sometimes it is helpful to use an analogy to better understand information about our genes and how we use genetic analyses to examine our genes.

 


46, XY; Male karyotype

Our chromosomes are like a set of 46 encyclopedia books. A chromosome analysis or karytype is able to determine if there are any missing or extra books (chromosomes).


Computerized results of a DNA Microarray

Our genes are like the sentences on each page of the set of encyclopedia books (chromosomes). Each page of each book contains a unique set of sentences (genes).  Each page contains the sentences for approximately 10 to 30 genes.   A DNA microarray analysis is able to open up each of the 46 encyclopedia books to determine if there are any missing or extra pages. Click here to learn more about DNA microarray analysis. 


Computerized results of genetic sequencing

Our DNA are like the letters that make up each sentence (gene) on each page of the books (chromosomes). Each sentence is made up of a very specific sequence of letters (DNA). Genetic sequencing is able read a specific sentence to determine if there are any spelling mistakes (genetic mutations) in the sentence (gene). Click here to learn more about genetic sequencing.


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