To understand how characteristics of living things are passed from generation to generation, a family tree, or pedigree is often used to illustrate the movement of the characteristic through each generation. The pedigree may involve single gene inheritance or the inheritance of multifactorial traits (multiple gene and environment interaction). A pedigree is a tool used to describe the relationships within a family; they use
lines, symbols, and shading to indicate family relationships and persons with a specific trait or condition. The table above displays the different components of a pedigree. There are many modes of inheritance for single genes, and each mode of inheritance follows a specific pedigree pattern. Below are links to example pedigrees with different modes of inheritance for single gene traits. Each of these pedigrees is designed to show the patterns for the corresponding inheritance pattern and
may not be typical for rare single gene conditions. However, each page also has some real examples of human traits that typically follow this mode of inheritance. Some also include realistic pedigrees for specific conditions. Autosomal Recessive Multifactorial Traits: Using the Pedigree as a Tool to Collect a Family History of Common Chronic DisordersUnlike single gene disorders that are very rare, common chronic disorders such as heart disease, cancer, and diabetes may, either directly or indirectly, impact all of our lives. These conditions have been found to run in families, and scientists now know that the appearance of these disorders is influenced by our genetics, environment, and behavior. Collecting family history with a pedigree for these chronic disorders is the first step toward prevention. Sometimes, assigning genotypes for family members at risk for multiple chronic disorders is not easy. That is because many common chronic conditions are not controlled by single genes but are multifactorial, meaning they are influenced by multiple genes and the environment. Most of our traits fall into this category. They are traits that vary slightly from individual to individual, such as height and hair color as well as common chronic conditions like heart disease, diabetes, and cancer. Genetic Variation:DNA is only as powerful as the proteins it produces. Proteins are products of gene expression that create our phenotype (traits and characteristics). Some genes work alone producing a protein that results in a phenotype for a single gene trait. Other genes work together along with the environment to create a phenotype for multifactorial conditions. In this situation, a certain combination of proteins (gene products) cause one phenotype while a different combination of proteins from the same genes can cause a different phenotype, resulting in genetic variation or a trait that varies slightly from individual to individual. Genes also have the ability to produce different proteins for a given trait. Each gene has multiple alleles or variations in the DNA sequence at the gene locus, which can result in variants (mutations) for that gene. When a genetic disorder is diagnosed in a family, family members often want to know the likelihood that they or their children will develop the condition. This can be difficult to predict in some cases because many factors influence a person's chances of developing a genetic condition. One important factor is how the condition is inherited. For example:
It is important to note that the chance of passing on a genetic condition applies equally to each pregnancy. For example, if a couple has a child with an autosomal recessive disorder, the chance of having another child with the disorder is still 25 percent (or 1 in 4). Having one child with a disorder does not “protect” future children from inheriting the condition. Conversely, having a child without the condition does not mean that future children will definitely be affected. Although the chances of inheriting a genetic condition appear straightforward, factors such as a person's family history and the results of genetic testing can sometimes modify those chances. In addition, some people with a disease-causing variant never develop any health problems or may experience only mild symptoms of the disorder. If a disease that runs in a family does not have a clear-cut inheritance pattern, predicting the likelihood that a person will develop the condition can be particularly difficult. Estimating the chance of developing or passing on a genetic disorder can be complex. Genetics professionals can help people understand these chances and help them make informed decisions about their health. What does diathesis mean?Definition of diathesis
: a constitutional predisposition toward a particular state or condition and especially one that is abnormal or diseased.
What is a predisposition toward developing a disorder?A genetic predisposition (sometimes also called genetic susceptibility) is an increased likelihood of developing a particular disease based on a person's genetic makeup. A genetic predisposition results from specific genetic variations that are often inherited from a parent.
Which of the following study types must be conducted to identify the location of specific genes associated with psychopathology?the approximate degree of influence of genetics for a specific psychological disorder. Which of the following study types must be conducted to identify the location of specific genes associated with psychopathology? a. genetic linkage analysis.
What describes the concept of validity as it applies to psychological assessment?Validity refers to how well a test actually measures what it was created to measure. Reliability measures the precision of a test, while validity looks at accuracy.
|