Concept explainers
CASE STUDY | To test or not to test
Thomas first discovered a potentially devastating piece of family history when he learned the medical diagnosis for his brother's increasing dementia, muscular rigidity, and frequency of seizures. His brother, at age 49, was diagnosed with Huntington disease (HD), a dominantly inherited condition that typically begins with such symptoms around the age of 45 and leads to death in one's early 60s. As depressing as the news was to Thomas, it helped explain his father's suicide. Thomas, 38, now wonders what his chances are of carrying the gene for HD, leading him and his wife to discuss the pros and cons of him undergoing genetic testing. Thomas and his wife have two teenage children, a boy and a girl.
What role might a genetic counselor play in this real-life scenario?
To review:
The role or the job of a genetic counselor.
Introduction:
Genetics is a part of science that deals with the study of the genetic material of an organism. This science also involves studying the genetic variation, mutations, and their inheritance. Genetic studies are not just important in theory but have many practical aspects to it. For example, the study of genes is important in agriculture to develop better varieties of crops, and in medicine to treat diseases.
Explanation of Solution
The term genetic counselor is given to a person who helps to provide information on a genetic condition to any patientwho may be prone to or might be going through. This they do by performing genetic tests, analyzing the data, analyzing the history of the patient’s family for genetic disorders like cancers, other diseases like muscular dystrophy, cystic fibrosis, etcetera, and then educating the patient for the same. Their job is not to tell the patient what decision they should take, but just to make the information available and talk them through difficult decisions.
They usually work in hospitals or clinics or genetic laboratories and help the patients to tackle the results of the diagnosis.
Thus, it can be concluded thata genetic counselor is the one who provides the patient with the important information of the genetic disorder to the patient might be suffering through or be prone to that disease. They also help to deal with the emotional setbackthat the patient goes through after the diagnosis.
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Chapter 3 Solutions
Essentials of Genetics (9th Edition) - Standalone book
- Question:- Based on your selected mode of inheritance, show the genotypes for the following individuals. [Use these symbols for alleles: if it is autosomal, then use the symbols B - dominant, b - recessive (e.g. BB, bb etc.) if it is X-Linked, then X(B) - dominant, X(b) - recessive, and Y for Y-chromosome (e.g. X(B)X(B), X(B)Y etc.) ] I-1 I-2 II-7 II-8 III-10 III-11 III-12 IV-8 IV-9arrow_forwardMike was referred for genetic counseling because he was concerned about his extensive family history of colon cancer. That family history was highly suggestive of hereditary nonpolyposis colon cancer (HNPCC). This predisposition is inherited as an autosomal dominant trait, and those who carry the mutant allele have a 75% chance of developing colon cancer by age 65. Mike was counseled about the inheritance of this condition, the associated cancers, and the possibility of genetic testing (on an affected family member). Mikes aunt elected to be tested for one of the genes that may be altered in this condition and discovered that she did have an altered MSH2 gene. Other family members are in the process of being tested for this mutation. Once a family member is tested for the mutant allele, is it hard for other family members to remain unaware of their own fate, even if they did not want this information? How could family dynamics help or hurt this situation?arrow_forwardMike was referred for genetic counseling because he was concerned about his extensive family history of colon cancer. That family history was highly suggestive of hereditary nonpolyposis colon cancer (HNPCC). This predisposition is inherited as an autosomal dominant trait, and those who carry the mutant allele have a 75% chance of developing colon cancer by age 65. Mike was counseled about the inheritance of this condition, the associated cancers, and the possibility of genetic testing (on an affected family member). Mikes aunt elected to be tested for one of the genes that may be altered in this condition and discovered that she did have an altered MSH2 gene. Other family members are in the process of being tested for this mutation. Seventy-five percent of people who carry the mutant allele will get colon cancer by age 65. This is an example of incomplete penetrance. What could cause this?arrow_forward
- A couple was referred for genetic counseling because they wanted to know the chances of having a child with dwarfism. Both the man and the woman had achondroplasia (MIM 100800), the most common form of short-limbed dwarfism. The couple knew that this condition is inherited as an autosomal dominant trait, but they were unsure what kind of physical manifestations a child would have if it inherited both mutant alleles. They were each heterozygous for the FGFR3 (MIM 134934) allele that causes achondroplasia. Normally, the protein encoded by this gene interacts with growth factors outside the cell and receives signals that control growth and development. In achrodroplasia, a mutation alters the activity of the receptor, resulting in a characteristic form of dwarfism. Because both the normal and mutant forms of the FGFR3 protein act before birth, no treatment for achrondroplasia is available. The parents each carry one normal allele and one mutant allele of FGRF3, and they wanted information on their chances of having a homozygous child. The counsellor briefly reviewed the phenotypic features of individuals with achondroplasia. These include facial features (large head with prominent forehead; small, flat nasal bridge; and prominent jaw), very short stature, and shortening of the arms and legs. Physical examination and skeletal X-ray films are used to diagnose this condition. Final adult height is approximately 4 feet. Because achondroplasia is an autosomal dominant condition, a heterozygote has a 1-in-2, or 50%, chance of passing this trait to his or her offspring. However, about 75% of those with achondroplasia have parents of average size who do not carry the mutant allele. In these cases, achondroplasia is due to a new mutation. In the couple being counseled, each individual is heterozygous, and they are at risk for having a homozygous child with two copies of the mutated gene. Infants with homozygous achondroplasia are either stillborn or die shortly after birth. The counselor recommended prenatal diagnosis via ultrasounds at various stages of development. In addition, a DNA test is available to detect the homozygous condition prenatally. Should the parents be concerned about the heterozygous condition as well as the homozygous mutant condition?arrow_forwardA couple was referred for genetic counseling because they wanted to know the chances of having a child with dwarfism. Both the man and the woman had achondroplasia (MIM 100800), the most common form of short-limbed dwarfism. The couple knew that this condition is inherited as an autosomal dominant trait, but they were unsure what kind of physical manifestations a child would have if it inherited both mutant alleles. They were each heterozygous for the FGFR3 (MIM 134934) allele that causes achondroplasia. Normally, the protein encoded by this gene interacts with growth factors outside the cell and receives signals that control growth and development. In achrodroplasia, a mutation alters the activity of the receptor, resulting in a characteristic form of dwarfism. Because both the normal and mutant forms of the FGFR3 protein act before birth, no treatment for achrondroplasia is available. The parents each carry one normal allele and one mutant allele of FGRF3, and they wanted information on their chances of having a homozygous child. The counsellor briefly reviewed the phenotypic features of individuals with achondroplasia. These include facial features (large head with prominent forehead; small, flat nasal bridge; and prominent jaw), very short stature, and shortening of the arms and legs. Physical examination and skeletal X-ray films are used to diagnose this condition. Final adult height is approximately 4 feet. Because achondroplasia is an autosomal dominant condition, a heterozygote has a 1-in-2, or 50%, chance of passing this trait to his or her offspring. However, about 75% of those with achondroplasia have parents of average size who do not carry the mutant allele. In these cases, achondroplasia is due to a new mutation. In the couple being counseled, each individual is heterozygous, and they are at risk for having a homozygous child with two copies of the mutated gene. Infants with homozygous achondroplasia are either stillborn or die shortly after birth. The counselor recommended prenatal diagnosis via ultrasounds at various stages of development. In addition, a DNA test is available to detect the homozygous condition prenatally. What is the chance that this couple will have a child with two copies of the dominant mutant gene? What is the chance that the child will have normal height?arrow_forwardA couple was referred for genetic counseling because they wanted to know the chances of having a child with dwarfism. Both the man and the woman had achondroplasia (MIM 100800), the most common form of short-limbed dwarfism. The couple knew that this condition is inherited as an autosomal dominant trait, but they were unsure what kind of physical manifestations a child would have if it inherited both mutant alleles. They were each heterozygous for the FGFR3 (MIM 134934) allele that causes achondroplasia. Normally, the protein encoded by this gene interacts with growth factors outside the cell and receives signals that control growth and development. In achrodroplasia, a mutation alters the activity of the receptor, resulting in a characteristic form of dwarfism. Because both the normal and mutant forms of the FGFR3 protein act before birth, no treatment for achrondroplasia is available. The parents each carry one normal allele and one mutant allele of FGRF3, and they wanted information on their chances of having a homozygous child. The counsellor briefly reviewed the phenotypic features of individuals with achondroplasia. These include facial features (large head with prominent forehead; small, flat nasal bridge; and prominent jaw), very short stature, and shortening of the arms and legs. Physical examination and skeletal X-ray films are used to diagnose this condition. Final adult height is approximately 4 feet. Because achondroplasia is an autosomal dominant condition, a heterozygote has a 1-in-2, or 50%, chance of passing this trait to his or her offspring. However, about 75% of those with achondroplasia have parents of average size who do not carry the mutant allele. In these cases, achondroplasia is due to a new mutation. In the couple being counseled, each individual is heterozygous, and they are at risk for having a homozygous child with two copies of the mutated gene. Infants with homozygous achondroplasia are either stillborn or die shortly after birth. The counselor recommended prenatal diagnosis via ultrasounds at various stages of development. In addition, a DNA test is available to detect the homozygous condition prenatally. What if the couple wanted prenatal testing so that a normal fetus could be aborted?arrow_forward
- 2) Indicate the pattern of inheritance for the human genetic disorders. Use letter symbols for your answers (AR, AD, XR,XD, M) where appropriate. Table 2. HUMAN GENETIC DISORDER PATTERN OF INHERITANCE Marfan Syndrome Sickle Cell Anemia Classical Hemophilia Hypophosphatemia Cystic Fibrosis Phenylketonuria Huntington’s Disease Tay Sachs Disease Neurofibromatosis Alkaptonuria Xeroderma pigmentosum Kearns-Sayre Syndrome Achondroplasia Beta thalassemia Duchene Muscular Dystrophyarrow_forwardAav AaBbCc Normal No Spacing Heading 1 Paragraph Styles In man, two abnormal conditions, cataracts (C) in the eyes and excessive fragility (F) in the bones, seem to depend on separate dominant genes located on different chromosomes. Normal vision and normal bones are recessive traits. A man with cataracts and nomal bones, whose father had normal eyes, married a woman free from cataracts but with fragile bones. Her father had normal bones. 11. What is the genotype of the man with cataracts and nomal bones? What is the genotype of the woman with normal vision and fragile bones? What type of offspring might this couple expect? Genotypes Phenotypes What is the probability that their first child will, (a) be free from both abnormalities (b) have cataracts but not fragile bones (c) have fragile bones but not cataracts (d) have both cataracts and fragile bones? liliarrow_forwardLet us practice it again! Analyze the pedigree below to answer the questions that follow. Huntington's disease a disorder in which nerve cells waste away, or disintegrate, is passed down through families. certain parts of the brain Huntington's diseate llustration ereated in htps://pregenygenetion.com/ 1. What members of the family above are affected with the Huntington's disease? 2. Tnere are no carriers ior Huntungton's disease you either have it or you do not. Is Huntington's disease caused-by a dominant or recessive trait? 3. Identify the genotypes of the following individuals using the pedigree above. (homozygous dominant, homozygous recessive, heterozygous). I- 1 II -1: II -3: III - 4 : 4. How many children did individuals I-1 and I-2 have? 5. How many girls did II-1 and II-2 have? How many have Huntington's Disease? 6. How are individuals III-2 and II-4 related? I-2 and III-5?arrow_forward
- Question:- 8. Describe how Morgan’s experiment with the white-eyed mutant fly provided evidence for the chromosomal basis for inheritance. Be sure to include the significance of the x-linked gene.arrow_forwardTOPIC: Sex-linked inheritance Glucose-6-phosphate dehydrogenase deficiency/G6PDD (g) is an X-linked recessive condition wherein the red blood cells of affected individuals undergo premature hemolysis. Fragile X syndrome (F), on the other hand, is an X-linked dominant mutation characterized by a mild to moderate intellectual disability. Amelogenesis imperfecta (AMELY) (A) is a sex-linked congenital disorder affecting the formation of the teeth enamel making affected individuals at higher risk for dental cavities and related problems. Only male offspring inherit this condition. Jane is heterozygous for both X-linked traits like her mother. Her father is normal for both X-linked traits. James has a mother who suffers from G6PDD but not from fragile X-syndrome. His father does not exhibit any X-linked disorder but has amelogenesis imperfecta. What are the genotypes of the following: Jane: ________ James: _________ Jane’s mother: __________…arrow_forwardMelanoma, 45 Colon cancer, 40 Sarcoma, 45 Breast Lung cancer, 53 cancer, 32 Stomach cancer, 50 Brain cancer, 18 Osteosarcoma, 3 Leukemia, 19 Rhabdomyosarcoma, 14 Answer the following subparts :- A. What do you notice in this pedigree as compared to Rb or BRCA1/2? B. Why do you think that so many cancer types are associated with inherited defects in p53? Please need detailed answer I want to learn please please I will upvote god promise|arrow_forward
- Human Heredity: Principles and Issues (MindTap Co...BiologyISBN:9781305251052Author:Michael CummingsPublisher:Cengage Learning