Study with the several resources on Docsity
Earn points by helping other students or get them with a premium plan
Prepare for your exams
Study with the several resources on Docsity
Earn points to download
Earn points by helping other students or get them with a premium plan
Community
Ask the community for help and clear up your study doubts
Discover the best universities in your country according to Docsity users
Free resources
Download our free guides on studying techniques, anxiety management strategies, and thesis advice from Docsity tutors
Essential information on inheriting genetic conditions, including degrees of relationship, ways of inheritance, and common examples. Learn about X-linked, codominant, mitochondrial, and other inheritance patterns. Understand concepts like reduced penetrance, variable expressivity, and anticipation.
Typology: Lecture notes
1 / 30
This page cannot be seen from the preview
Don't miss anything!
Inheriting Genetic Conditions Inheriting Genetic Conditions Table of Contents Section Page What does it mean if a disorder seems to run in my family? 3 Why is it important to know my family medical history? 6 What are the different ways in which a genetic condition can be inherited? 8 If a genetic disorder runs in my family, what are the chances that my children will have the condition?
What are reduced penetrance and variable expressivity? 23 What do geneticists mean by anticipation? 25 What are genomic imprinting and uniparental disomy? 26 Are chromosomal disorders inherited? 28 Why are some genetic conditions more common in particular ethnic groups?
Inheriting Genetic Conditions This condition affects members in each generation of a family. For general information about disorders that run in families: Genetics Home Reference provides consumer-friendly summaries of genetic conditions (https://ghr.nlm.nih.gov/condition). Each summary includes a brief description of the condition, an explanation of its genetic cause, and information about the condition's frequency and pattern of inheritance. The Coriell Personalized Medicine Collaborative provides a brief introduction to heritable diseases in the article Heredity: It Runs in the Family (https:// cpmc.coriell.org/genetic-education/it-runs-in-the-family).
Inheriting Genetic Conditions The Genetic Science Learning Center at the University of Utah offers interactive tools about disorders that run in families (http://learn.genetics.utah.edu/content/ history). The National Human Genome Research Institute offers a brief fact sheet called Frequently Asked Questions About Genetic Disorders (https:// www.genome.gov/19016930). The Centre for Genetics Education provides an overview of genetic conditions (http://www.genetics.edu.au/publications-and-resources/facts-sheets/fact- sheet-5-genetic-conditions).
Inheriting Genetic Conditions For more information about family medical history: Educational resources related to family health history (https:// geneed.nlm.nih.gov/topic_subtopic.php?tid=5&sid=13) are available from GeneEd. Additional information about family history (https://medlineplus.gov/ familyhistory.html) is available from MedlinePlus. The Centers for Disease Control and Prevention's (CDC) Office of Public Health Genomics provides information about the importance of family medical history (https://www.cdc.gov/genomics/famhistory/). This resource also includes links to publications, reports, and tools for recording family health information. The Office of the Surgeon General offers a tool called My Family Health Portrait (https://familyhistory.hhs.gov/) that allows you to enter, print, and update your family health history. The American Medical Association provides family history tools (https:// www.ama-assn.org/delivering-care/collecting-family-history), including questionnaires and forms for collecting medical information. The National Institute on Aging provides suggestions on how to obtain a health history form older individuals (https://www.nia.nih.gov/health/obtaining-older-patients-medical- history). The Genetic Alliance also offers a list of links to family history resources (http:// www.geneticalliance.org/programs/genesinlife/fhh).
Inheriting Genetic Conditions What are the different ways in which a genetic condition can be inherited? Some genetic conditions are caused by mutations in a single gene. These conditions are usually inherited in one of several patterns, depending on the gene involved: Patterns of inheritance Inheritance pattern Description Examples Autosomal dominant One mutated copy of the gene in each cell is sufficient for a person to be affected by an autosomal dominant disorder. In some cases, an affected person inherits the condition from an affected parent (image on page 12 ). In others, the condition may result from a new mutation (image on page 13 ) in the gene and occur in people with no history of the disorder in their family. Huntington disease, Marfan syndrome Autosomal recessive In autosomal recessive inheritance (image on page 14 ), both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition. Autosomal recessive disorders are typically not seen in every generation of an affected family. cystic fibrosis, sickle cell disease
Inheriting Genetic Conditions Inheritance pattern Description Examples Codominant In codominant inheritance (image on page 18 ), two different versions (alleles) of a gene are expressed, and each version makes a slightly different protein. Both alleles influence the genetic trait or determine the characteristics of the genetic condition. ABO blood group, alpha-1 antitrypsin deficiency Mitochondrial Mitochondrial inheritance (image on page 19 ), also known as maternal inheritance, applies to genes in mitochondrial DNA. Mitochondria, which are structures in each cell that convert molecules into energy, each contain a small amount of DNA. Because only egg cells contribute mitochondria to the developing embryo, only females can pass on mitochondrial mutations to their children. Conditions resulting from mutations in mitochondrial DNA can appear in every generation of a family and can affect both males and females, but fathers do not pass these disorders to their daughters or sons. Leber hereditary optic neuropathy (LHON) Many health conditions are caused by the combined effects of multiple genes or by interactions between genes and the environment. Such disorders usually do not follow the patterns of inheritance described above. Examples of conditions caused by multiple genes or gene/environment interactions include heart disease, diabetes, schizophrenia, and certain types of cancer. For more information, please see What are complex or multifactorial disorders? (https:// ghr.nlm.nih.gov/primer/mutationsanddisorders/complexdisorders) Disorders caused by changes in the number or structure of chromosomes also do not follow the straightforward patterns of inheritance listed above. To read about how chromosomal conditions occur, please see Are chromosomal disorders inherited? on page 28 Other genetic factors sometimes influence how a disorder is inherited. For an example, please see What are genomic imprinting and uniparental disomy? on page 26
Inheriting Genetic Conditions For more information about inheritance patterns: Resources related to heredity/inheritance patterns (https://geneed.nlm.nih.gov/ topic_subtopic.php?tid=5) and Mendelian inheritance (https:// geneed.nlm.nih.gov/topic_subtopic.php?tid=5&sid=6) are available from GeneEd. The Centre for Genetics Education provides information about many of the inheritance patterns outlined above:
Inheriting Genetic Conditions In this example, a child with an autosomal dominant condition has the disorder as a result of a new (de novo) mutation that occurred during the formation of an egg or sperm cell or early in embryonic development.
Inheriting Genetic Conditions In this example, two unaffected parents each carry one copy of a gene mutation for an autosomal recessive disorder. They have one affected child and three unaffected children, two of which carry one copy of the gene mutation.
Inheriting Genetic Conditions In the example on the left, a father with an X-linked recessive condition has two daughters that are carriers of the causative mutation. On the right, a mother who is a carrier of an X-linked recessive disorder has one affected son and one daughter who is also a carrier.
Inheriting Genetic Conditions In this example, a father with a Y-linked condition has two affected sons. His daughters are unaffected.
Inheriting Genetic Conditions In the family on the left, a woman with a disorder caused by a mutation in mitochondrial DNA and her unaffected husband have children who are all affected by the condition. In the family on the right, a man with a condition resulting from a mutation in mitochondrial DNA and his unaffected wife have no affected children.
Inheriting Genetic Conditions If a genetic disorder runs in my family, what are the chances that my children will have the condition? 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:
