What are genes?
Genes are the unit of heredity in all living organisms. They are long strings of deoxyribonucleic acid (DNAAbbreviation for deoxyribonucleic acid. Composed of very long strings of nucleotides, which are abbreviated as A, C, G and T. DNA is the storage form of our genetic material. All of the instructions for the production of proteins are encoded in our DNA. ). The collection of genes in a person acts as a blueprint for the entire body. Everything from your eye color to your height and even some personality traits can be coded for in your DNA. The collection of genes that an individual has is referred to as their genomeThe full set of genes in an organism. Humans have an estimated 25,000 protein-encoding genes in their genome.. In humans, the genome is located on 46 chromosomes (other animals and plants have different numbers of chromosomes). Chromosomes in an individual are inherited - one set of 23 comes from the mother and the other set of 23 comes from the father. Just as a language is made up of letters and words, genes are made up of a set of 4 building blocks, called nucelotides. The chemical names for the four nucleotides in DNA are abbreviated as A, C, G, and T. Some genes contain the information that guides the production of proteins. In these genes the DNA “letters” are organized into three letter ‘words’. These triplets are precursors to the ‘codons’ found in messenger RNAAlso: ribonucleic acid. RNA is a polymer comprised of the nucleotides A, C, G and U. RNA is the working form of our genetic information. RNA is produced via the process of transcription. Some RNA is used to help build ribosomes (rRNA) and some (mRNA) are used to guide the formation of proteins. Other forms of RNA are used to perform specialized functions in the nucleus.. They guide the formation of proteins; each three-letter codonA string of three adjacent nucleotides along a messenger RNA (mRNA) molecule that encodes a single amino acid. Ribosomes are able to 'read' the encoded message in an mRNA and synthesize proteins from amino acids present in the cell. guides the insertion of a single amino acidA monomer building block used to build proteins. There are many amino acids but only about twenty different kinds are found in most proteins..
Learn about cancer-related genes.
What are genetic mutations?
Damage to DNA can lead to changes in the encoded information. These changes are called mutations. Some mutations can cause diseases, including cancer. Genetic testing technology gives some people the option of finding out which mutations caused their cancer, or whether they have inherited a geneA stretch of DNA that leads to the production of an RNA. The RNA is produced during the process of transcription. This RNA can be used to guide the formation of a protein via translation or can be used directly in the cell. mutation that may cause cancer in the future. Genetic changes that are found in a peson's eggs or sperm can be passed down their children. These changes may to lead to cancer and many of them can be identified by genetic tests.If the human genome were a book, genetic testing would be like looking for typos. These typos can be caused by harmful environmental factors, such as chemicals in cigarette smoke or UV rays from the sun, or they can be inherited and passed down through families. Some mutations almost always cause cancer, while others can just increase the patient’s risk for particular cancers. It is important to remember that we all have the genes that are associated with cancer risk. For example, everyone has the BRCA1 gene. It is mutations in BRCA1 that can increase cancer risk. It is the mutations that genetic tests are designed to find.
There are different types of mutations that alter the DNA sequence of a gene. Mutations can vary in severity – some have no known effects and others can have large health effects.
Learn more about mutations and their effects.
What is genetic testing? Who is it for?
Genetic testing can be done before or after diagnosis. Predictive or preventative tests are sometimes recommended for those who have a family history of cancer, or have been exposed to a harmful agent that could put them at high risk, like cigarette smoke or UV radiationIn cancer biology: A cancer treatment in which high energy beams are used to kill cancer cells. Radiation can also cause genetic damage that can lead to cancer. As an example, skin cancer is believed to be greatly increased by exposure to ultraviolet (UV) radiation from the sun.. Diagnostic tests are recommended for those who have just been diagnosed with a cancer that may be treated with targeted therapies or checkpoint inhibitor immunotherapies. The tests help the patient and physician decide which course of treatment will be most effective. Depending on the condition, tests can be performed on tumor samples, blood samples, or hair and skin samples. These samples are sent to a laboratory, where technicians look for abnormalities in chromosomeA long DNA molecule containing genetic information (genes). Humans have 46 chromosomes. One set of 23 is inherited from each parent. A full set of chromosomes is present in the nucleus of each human cell. structure, proteins, and/or DNA sequences. 1
Learn about genetic testing at the Winship Cancer Institute of Emory University.
Cells from blood or other tissues can be examined to look for genetic changes (mutations) that could be linked to cancer. Testing can be done on patients without cancer or on cancer itself. The results can be used to determine possible prevention or treatment options.
Hereditary (familial) Cancers
Inherited cancers are usually caused by a mutation in a tumor suppressorA gene that functions in the control of cell division. Tumor suppressors normally work to limit cell division and may be contrasted with oncogenes. gene. A tumor suppressor is a proteinOne of the four basic types of biomolecule. Proteins are polymers made up of strings of amino acids. Proteins serve many functions in organisms including transport of molecules, structure, cell adhesion and as signaling molecules such as hormones. Many transcription factors, including p53 and Rb are proteins. that regulates cell division and other related processes. Tumor suppressors are responsible for DNA damage repair, and to make sure that cells with damage do not continue dividing. When a person inherits a genetic mutation in any gene, the mutation is present in every cell in their body, since each cell is equipped with the same genetic code. However, in order for cancer to actually form, a second mutation must occur in a cell. This concept is known as the “Two Hit Hypothesis”. Those with an inherited genetic mutation already have one hit in every cell. These individuals are more susceptible to cancer because it is very likely that another mutation will occur in a cell at some time, causing that particular cell to have 2 hits, and potentially divide out of control.
Genetic testing can use used to detect mutations associated with several types of cancer, including some forms of breast cancer, colon cancer, eye cancer, kidney cancer, and endocrine cancers.
Learn more about hereditary cancers and their gene mutations.
Do genetic mutations occur throughout life?
The short answer is 'Yes'. Genetic mutations that occur randomly are known as spontaneous mutations. Spontaneous mutations can occur in tumor suppressor genes, and can also occur in proto-oncogenes. Proto-oncogenes drive cell division forward and are often transcription factors or growth factors, meaning they are responsible for telling a cell to start copying (replicating) its DNA. When a proto-oncogeneA gene that normally functions to promote cell division. When these genes are mutated they may produce products that promote cell division in an abnormal fashion. Examples of oncogenes include HER2/neu, ras, and src. See Tumor Suppressors and Oncogenes for more details. gets mutated and becomes abnormal, it is referred to as an oncogeneA defective gene that is involved in triggering cancer cell growth. Oncogenes are altered forms of genes that normally are involved stimulating cell division. These normal genes are mutated and function in an inappropriate manner in cancer cells. An analogy would be that a mutated oncogene is like a car's gas pedal stuck in the on position. All forms of cancer have one or more mutant oncogenes. Examples of oncogenes that are altered in many cancers are myc, ras and Her-2/neu. Contrast with 'tumor suppressor'.. A big difference between oncogenes and tumor suppressors is that mutations in oncogenes are usually ‘dominant’, meaning only one copy of the gene needs to be defective to cause damage. Mutations in oncogenes are rarely inherited because they often result in embryonic lethality. However, two known exceptions to this are oncogenes RET and CDK4. Both RET and CDK4 encode for protein kinases. RET is implicated in familial thyroid carcinomas, and CDK4 is implicated in familial melanoma.2 On the otherhand, mutations in tumor suppressors are typically recessive, meaning that in most cases, both copies must be defective to cause damage (note that humans have two copies of most of their genes - one copy from each parent).
There are many different oncogenes, and it is safe to say that at least one oncogene will be active in any given case of cancer. Genetic testing for specific oncogenic mutations can be very important for designing treatment plans. By finding out the mutation(s) that caused the cancer, physicians are better able to determine a patient's course of treatment, such as whether or not to use immunotherapies, targeted therapies, or chemotherapies. Immunotherapies work by boosting a patient's immune system, so that it is better able to kill cancer cells. Current targets of immunotherapies are CTLA-4 and PD-1 receptors. 3 Examples of immunotherapies include: Yervoy® (ipilimumab), Opdivo® (nivolumab), and Keytruda® (pembrolizumab). Targeted therapies work by binding specific oncoproteins. For example, the drug Herceptin® (trastuzumab) targets the HER2/neuAlso: erbB-2. A transmembrane growth factor receptor protein, found at very high levels on some breast and ovarian cancers and may be a prognostic factor in these types of cancer. The cancer treatment Herceptin is a monoclonal antibody selected to attack cells that express high levels of this protein on their surface. oncogene product present in some breast cancers. Bcr/Abl, a mutant protein that drives chronic myeloid leukemiaA cancer affecting the cells that develop into white or red blood cells. Both of these cell types originate from stem cells in bone marrow. Red blood cells function to carry oxygen to our tissues and the white cells (leukocytes) are part of our immune system. The cancerous cells often accumulate in the blood., is blocked by the drug Gleevec® (imatinib) and other drugs. Tarceva® (erlotinib) and Gilotrif® (afatinib) target EGFR, a cell surface receptor protein that is mutated in some patients with non-small cell lung cancer (NSCLC). Other cancers caused by mutations for which there are tests include acute lymphocytic leukemia, gastrointestinal stromal tumors (GIST), non-Hodgkin lymphomaA cancer arising in the lymphatic system. The white blood cells affected are part of the body's immune system. The lymphatic system is a large network of vessels that carry fluid and cells of the immune system around the body. Lymph nodes are regional collection centers in the lymphatic system. See also, 'lymphatic system'., and melanoma.
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