Hello!
Thank you for watching our video discussing basic genetic concepts.
I am a member of the GenomeConnect and ClinGen Patient Data Sharing Program team.
Each of us have millions and millions of cells that make up our bodies.
We have different types of cells such as skin cells, brain cells, and heart cells that are
our body s building blocks.
Our cells contain structures called chromosomes.
Chromosomes hold our genetic information or our DNA.
Our DNA is our body s instruction manual, telling our bodies how to develop and function.
Chromosomes keep all of our genetic information packaged into our cells.
Typically, people have 46 chromosomes that come in 23 pairs.
Our chromosomes come in pairs because we get one set from each biological parent.
The first 22 pairs of chromosomes are typically the same in individuals and are organized
based on size with chromosome 1 being the largest and chromosome 22 being the smallest.
The 23rd pair of chromosomes are called our sex chromosomes.
Most people have two sex chromosomes.
Some individuals have one X and one Y and some have two X s.
Individuals assigned male at birth most often have an X and a Y and individuals assigned
female at birth most often have two X.
As previously mentioned, our chromosomes are made up of tightly wound DNA.
Our DNA is our body s instruction manual, and each instruction is called a gene.
Each gene provides instructions for how our body makes proteins.
Our genes and proteins determine things such as eye color, heart development, brain development
and many other functions and development of our bodies.
Our DNA and each gene is made up of letters.
Those letters are A, T, G, and C. These letters are called nucleotides.
Our body reads these letters to make proteins.
When our body reads these letters to make proteins, the letters are read in sets of
three.
This is called the triplet code or codons.
The triplet code, codes for one part in the protein and the protein is made up of many
parts called amnio acids.
In this example, our body would read ATG and make one amnio acid for that group of letters.
Then, CAC to make a second, and so on.
Once all the letters are read and amnio acids are made, the protein is built and ready to
help our bodies function and develop.
There are twenty different amnio acids that make up our proteins all coded by sets of
three letters.
Some letter combinations tell the protein when it s complete and no additional letters
are added.
These are called stop codons.
Most of our DNA sequence is the same person to person, however we all have many changes
in our DNA.
These changes are called variants.
There can be many different types of variants.
Some may not have an effect on our health, whereas others may cause health concerns or
developmental differences.
There are two main categories of genetic variants copy number variants and sequence variants.
Copy number variants are genetic changes where a person has, often thousands of extra or
missing letters within their DNA.
These are large missing or extra pieces of genetic material.
If a person is missing genetic material this is called a deletion.
If they have an extra piece of genetic material, this is called a duplication.
So, if we think about our genetic material being like a shelf of instruction manuals,
a copy number variant means that a person is missing books or has extra books.
Copy number variants are typically named for their location.
As an example, you might see a report that says 19p13.3 deletion.
This indicates that the person has a missing piece of genetic material on one of their
number 19 chromosomes.
When we talk about chromosomes, we divide them into two parts the p and q arms.
The p arm is the short arm and q is the long arm.
So 19p tells us this deletion is on the short arm of chromosome 19.
You can see that the chromosomes have a banding or striped pattern.
This is actually what they look like under the microscope.
The 13.3 of 19p13.3 tells us exactly what band or stripe of the chromosome has the deletion.
The other type of genetic variants we will briefly mention are sequence variants.
Sequence variants mean there is a change to the letters within a gene.
Sometimes this is a single letter that is different other times it is a few letters.
If we think of our genetic material as a shelf of instruction manuals again, a sequence variant
is like there being a spelling change in a sentence of one of the books.
For more information about variants, watch our other videos!
Thank you for watching our types of genetic testing video.
If you have general questions about splice variants or other genetics-related topics
you can reach out to us at info@genomeconnect.org, or calling 570-214-1721 toll free 1-855-322-7683.
If you have questions about your genetic test results, we encourage you to reach out to
your doctor or genetic counselor.