What is the difference between a CNV and a change in one gene?

As you learned from previous sections about genetics and DNA, chromosomes are the structures that contain and organize all of our genes.

The following pictures may help to illustrate two different types of genetic changes that we study: copy number variants and genetic changes in one gene.

  • Imagine that the genome is a library where the DNA sequence is written in all the books.
    • Each chromosome is like a bookshelf.
    • Each book is a segment of the DNA sequence (several genes).
    • Each page in a book is a gene.
  • Each gene provides a specific set of instructions for the body and has a specific location in the DNA sequence so the body knows where to find the instructions it needs.


Example of a copy number variant (CNV):

A copy number variation means that in a person’s genome, one or more whole genes are missing or extra. These are called deletions and duplications of material.

  • If there are extra or missing books (segments of DNA containing multiple genes), the body may not be able to function correctly.


Examples of a change in one gene:

A genetic change in one gene might result in onepage of a book (or gene) to be missing from the shelf (chromosome).

  • If an important page of a book (gene) is missing, the body may not be able to function correctly.

A genetic change in one gene may also be caused by typo, or misspelling, in a sentence on the page of a book (or gene) that might result in the gene having a different function.  Depending on the specific genetic change, the “typo” in the sentence may change the entire story (more severe genetic change) or may just change what happens in the chapter (less severe genetic change).

  • If a typo or misspelling causes a page of a book (gene) to not be read correctly the body may not be able to function correctly.
 

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