Basic Genetics for Adults

[INTRO SLIDE]

INTRO TO GENETICS. Helping you understand the science behind your child's care. Mikayla Jennings, MS, CGC. Presented by [Shriners Children's logo, Greenwood Genetic Center logo]

Mikayla Jennings, Genetic Counselor: Hi, my name is Mikayla Jennings and I’m a clinical genetic counselor at the Greenwood Genetic Center. I’m here to talk to you today about genetics and how genetic testing can give us important information about your health.

So, what do we mean when we talk about genetics?

[SLIDE 1]

Chromosome to Gene to Protein
A simplified scientific diagram showing how biological information flows from a cell → chromosomes → genes → DNA → proteins.

• On the left is a yellow illustration of a cell, with a nucleus shown as a circular structure containing scribble‑like blue lines representing DNA.
• Next to the cell is a pair of blue chromosomes, each drawn as an X‑shaped structure with banding patterns. A label states that each chromosome is a long, continuous DNA molecule.
• Moving right, a zoom‑in of a DNA double helix shows its twisting structure with colored nucleotide pairs that encode a protein product.
• Beneath the DNA are labels for the four nucleotides:
  • Adenine
  • Thymine
  • Guanine
  • Cytosine
• Further to the right, a chain of blue spheres represents a protein molecule.
• Text explains that genes are DNA segments that encode proteins, and proteins are organic compounds made of amino acids.

Mikayla: Every cell in your body has genetic information called DNA. We refer to the collection of all of our DNA as our genome. You can think about the genome as a recipe book that tells the body how to grow, develop and function. That recipe book contains everything that makes you who you are: from your eye color, to your hair color, to even what health problems you might be at risk for.

This genomic recipe book is split up into chapters, which we call chromosomes.

[SLIDE 2]

Idiogram Karyotype

A grid‑like arrangement of chromosome pairs numbered 1–22 plus X and Y, shown in black‑and‑white banding typical of a karyotype.

• Chromosomes are arranged in 23 pairs, each pair having two vertically oriented, striped chromosomes.
• Pairs 1–22 appear in rows from left to right, largest to smallest.
• The final pair is labeled X and Y.
• Footer references “Cytogenetics.”

Mikayla: Typically, individuals have 46 chromosomes, which come in pairs. Our chromosomes are in pairs because we typically get one copy of each chromosome from the egg cell, and one copy of each chromosome from the sperm cell.

Within each of these chromosomes, or chapters of our genomic recipe book, you will find what we call genes.

[SLIDE 3]

Types of Gene Mutations
A visual metaphor comparing chromosomes and genes to chapters and sentences in a book, followed by examples of different mutation types using simple sentences.

• A closed blue book represents chromosomes.
• An open book represents genes.
• To the right, the word "RED" becomes sample sentences such as “THE CAR WAS RED,” demonstrating how mutations can change meaning.
• Below are four categories:
  • Missense mutations: “THE CAR WAS RED.” → “THE CAR WAS HAT.” or “THE CAR WAS RDD.”
  • Nonsense mutations: “THE CAR WAS RED.” → “THE CAR...” (sentence cuts short).
  • Insertion mutations: Adding a letter or word, e.g., “THE CAR WAS RED.” → “THE CAR WAS RED RED.”
  • Deletion mutations: Removing letters, e.g., “THE CAR WAS RED.” → “THE ___ WAS RED” or “THE _AR WAS RED.”

Mikayla: We can think of genes as the sentences of this book, or the actual recipes that tell our body how to function. There are over 20,000 genes in the human genome, each code for proteins with a specific job. Many of these genes play important roles in keeping us healthy. Like a sentence, our genes are made up of a string of letters – in this case, those are letters of DNA. DNA uses only 4 letters: As, Ts, Cs, and Gs.

Genetic testing looks for specific types of genetic changes that can give us important information about your health.

[SLIDE 4]

Sequencing Methodologies
A comparison of four genetic sequencing approaches, using a book metaphor to show scope.

• Four side‑by‑side panels, each with a title, sample sentences, and a book illustration.
• Single gene sequencing:
  • Sample text: “The car was red. The car was rdd.”
  • Description: Looks for errors in one sentence in the book (one gene).
• Targeted gene panel sequencing:
  • Sample text includes multiple short sentences (car, boat, train).
  • Description: Looks for errors in a specific group of sentences in the book.
• Exome sequencing:
  • Illustration of an open book.
  • Description: Looks for errors in the most important chapters in the book (all protein‑coding regions).
• Whole genome sequencing:
  • Illustration of a closed book.
  • Description: Look for errors in every single word in the book (entire genome).

Mikayla: Different types of genetic tests look for different types of genetic changes. Whole Genome Sequencing is a specific type of test that looks for spelling changes – not only in the pieces of genes that code for proteins called exons – but also in the closely surrounding information called introns. These types of changes are known as sequence variants. This test also looks for small, missing or extra pieces of DNA known as deletions and duplications. These types of changes are known as copy number variants. This test looks for these types of variants, so we can understand how your genetics might be impacting how your body functions.

We all have changes in our DNA that make us who we are.

[SLIDE 5]

Secondary Findings
A DNA double helix illustration showing positions of “primary” and “secondary” genetic findings.

• A long DNA double helix stretches across the image in multicolored base‑pair segments.
• A square box on the left section highlights a Primary finding, described as:
  • “Genetic change related to patient’s current condition.”
• Two square boxes on the right section highlight secondary findings, described as:
  • “Medically important genetic changes, but not related to the patient’s current condition.”
• Below this are examples:
  • Cancer Predisposition
  • Heart Condition
• Bold text reading: It is up to you whether you would like our lab to report secondary findings.

Mikayla: However, whole genome sequencing is specifically looking for any changes that might impact your health. This could give us information about the cause of a symptom we already know about, or it could tell us about other health concerns to look out for in the future. This test can also report what we call secondary findings, which are changes in genes that increase the risk for things like cancer or heart disease. If you decide to do whole genome sequencing, you can decide if you want to learn about changes in these specific genes. For more information on the option to report secondary findings, please see the video on secondary findings.

There are three types of results that we can get back from genetic testing.

[SLIDE 6]

Potential Results of Genetic Testing
A Venn diagram with three overlapping circles describing possible outcomes of genetic testing.

• The left circle is blue, labeled “Normal.”
  • Text: “No clinically significant changes identified.”
• The right circle is red, labeled “Abnormal.”
  • Text: “Disease‑causing change identified.”
• The overlapping center area is purple, labeled “Variant of Uncertain Significance (VUS).”
  • Text: “Change identified but significance is unknown.”
• Title at the top: “Potential Results of Genetic Testing.”

Mikayla: The first is a positive result, which means that we found a genetic change that either explains existing symptoms or is likely to impact your health in another way. It’s important to keep in mind that whole genome sequencing can sometimes find results that we weren’t expecting, meaning you could learn about a health problem you didn’t realize you were at risk for.

We can also get a negative result from whole genome sequencing. A negative result from this test is reassuring, but doesn’t rule out all possible genetic causes for symptoms. If your testing is normal but your doctor suspects there is something more to be learned, additional genetic testing may be recommended.

Finally, our testing can identify uncertain results, which we call variants of uncertain significance. This means that whole genome sequencing found a variant in a gene, but we don’t know if this is changing how the gene functions or not. Over time, especially as this testing is done for more people, we learn more about uncertain results and can better understand if these changes are harmful or not.

We hope this helped you learn a little more about genetics and genetic testing with whole genome sequencing. Ultimately, our goal with this testing is to better understand you and your health and to help others understand how genetics may be impacting their health as well. We appreciate you taking the time to learn more and encourage you to reach out to your provider at Shriners Children’s Hospital if you have any questions. 

Brought to you in partnership by [Shriners Children's logo] [Greenwood Genetic Center logo]