Human Heredity: Principles and Issues (MindTap Course List)
11th Edition
ISBN: 9781305251052
Author: Michael Cummings
Publisher: Cengage Learning
expand_more
expand_more
format_list_bulleted
Videos
Textbook Question
Chapter 12, Problem 1CS
Mike 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). Mike’s 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?
Expert Solution & Answer
Summary Introduction
To discuss: The cause of incomplete penetrance in case of colon cancer.
Introduction: Cancer can be defined as a group of diseases, which involve abnormal growth of cells, and these cells have the ability to spread and invade other regions of the body. Colon cancer is defined as the uncontrolled growth of cells of the large intestine specifically colon which is the end region of the large intestine. Most colon cancers are benign but in some cases, it can be malignant as well. The cancer property is shown by adenomatous polyps that are cancerous tumors present in the large intestine.
In the given case, Mr. M has a family history of nonpolyposis colon cancer. About 75% of the population inheriting the mutant allele expresses it and the gene mutation responsible for the colon cancer is present on the MSH2 gene.
Explanation of Solution
Penetrance is the term used for describing the percentage of the population that expresses symptoms of the inherited allele. In the given case study, the penetrance is an example of incomplete penetrance. This is because, 75% of the population expresses the inherited allele for colon cancer. In complete inheritance, 100% of the population expresses the inherited allele. The mutation in the MSH2 requires certain trigger factors to turn normal cells into cancerous cells. Some people do not experience this type of cancer even after the presence of the mutated gene because of the choice of a healthy lifestyle. A healthy lifestyle includes low consumption of preservatives or any other mutagens; as a result, the rate of mutation becomes low.
Want to see more full solutions like this?
Subscribe now to access step-by-step solutions to millions of textbook problems written by subject matter experts!
Students have asked these similar questions
As a genetic counselor, you are asked to assess the risk for a couple with a family history of familial adenomatous polyposis (FAP) who are thinking about having children. Neither the husband nor the wife has colorectal cancer, but the husband has a sister with FAP. What is the probability that this couple will have a child with FAP? Are there any tests that you could recommend to help in this assessment?
Achondroplasia is an autosomal dominant disorder characterized by disproportionate short stature: the legs and arms of people with achondroplasia are short compared with the head and trunk. The disorder is due to a base substitution in the gene, located on the short arm of chromosome 4, that encodes fibroblast growth factor receptor 3 (FGFR3). Although achondroplasia is clearly inherited as an autosomal dominant trait, more than 80% of the people who have achondroplasia are born to parents with normal stature. This high percentage indicates that most cases are caused by newly arising mutations; these cases (not inherited from an affected parent) are referred to as sporadic. Studies have demonstrated that sporadic cases of achondroplasia are almost always caused by mutations inherited from the father (paternal mutations). In addition, the occurrence of achondroplasia is higher among the children of older fathers; approximately 50% of children with achondroplasia are born to fathers…
A young lady requested pre-marital genetic counselling because her sister had died in infancy of gangliosidosis, an autosomal recessive disease. What is the risk that this young lady has similarly affected offspring? What advice should be given?
Chapter 12 Solutions
Human Heredity: Principles and Issues (MindTap Course List)
Ch. 12.10 - If improved diagnostic tests are developed from...Ch. 12.10 - If you had cancer, would you donate tissue samples...Ch. 12.10 - Prob. 1GRCh. 12.10 - Another model, the random model, proposes that any...Ch. 12 - Mike was referred for genetic counseling because...Ch. 12 - Mike was referred for genetic counseling because...Ch. 12 - Mike was referred for genetic counseling because...Ch. 12 - Theodor Boveri predicted that malignancies would...Ch. 12 - Distinguish between a familial and a sporadic...Ch. 12 - Benign tumors: a. are noncancerous growths that do...
Ch. 12 - Prob. 4QPCh. 12 - Prob. 5QPCh. 12 - Prob. 6QPCh. 12 - Prob. 7QPCh. 12 - Prob. 8QPCh. 12 - What is the difference between a proto-oncogene...Ch. 12 - Distinguish between dominant inheritance and...Ch. 12 - Describe the likelihood of developing bilateral...Ch. 12 - Prob. 12QPCh. 12 - The search for the BRCA1 breast cancer gene...Ch. 12 - What are the roles of cellular proto-oncogenes,...Ch. 12 - Which of the following mutations will result in...Ch. 12 - Prob. 16QPCh. 12 - The following family has a history of inherited...Ch. 12 - You are in charge of a new gene therapy clinic....Ch. 12 - Prob. 19QPCh. 12 - Can you postulate a reason or reasons why children...Ch. 12 - Prob. 21QPCh. 12 - In Section 12-1, Julie is concerned that she may...Ch. 12 - Prob. 23QPCh. 12 - What are some factors that epidemiologists have...Ch. 12 - Smoking cigarettes has been shown to be associated...Ch. 12 - Prob. 26QPCh. 12 - Studies have shown that there are significant...
Knowledge Booster
Learn more about
Need a deep-dive on the concept behind this application? Look no further. Learn more about this topic, biology and related others by exploring similar questions and additional content below.Similar questions
- Mike 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. Is colon cancer treatable? What are the common treatments, and how effective are they?arrow_forwardY-linked Amelogenesis imperfecta (A), a congenital disorder that affects the formation of the teeth enamel making affected individuals at higher risk for dental cavities and related problems. X-linked dominant hypophosphatemia (H), a form of rickets or vitamin D deficiency that affects the bones which causes pain, osteoarthritis, and abnormal shapeabnormal shape. X-linked recessive progressive Duchenne muscular dystrophy (m), a muscular disorder, leading to an irreversible gradual wasting of skeletal muscles. Hannah, the same as her mom, is heterozygous for both X-linked traits. While her dad is suffering from both muscular dystrophy and hypophosphatemia. Hannah's husband, Joey has a mom suffering from musculardystrophy regardless of having normal bone conditions. His dad has been blessed with strong muscles and bones, however, he is suffering from amelogenesis imperfecta. What are the complete genotypes of each person?a. Joey's momb. Joey's dadc. Joeyd. Hannah's mome. Hannah's dad f.…arrow_forwardAs a genetic counselor, you inform Susan and John that a blood test for cystic fibrosis is available. would you recommend generic testing for Susan and John?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. What if the couple wanted prenatal testing so that a normal fetus could be aborted?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. Should the parents be concerned about the heterozygous condition as well as the homozygous mutant condition?arrow_forward
- In Section 12-1, Julie is concerned that she may develop breast cancer, but testing shows that she does not carry the rare high-risk BRCA1 and BRCA2 alleles. What if further testing showed that some of her aunts, her mother, and she carried a common low-risk allele for breast cancer. What would you recommend to Julie if you were her genetic counselor?arrow_forwardFamilial retinoblastoma, a rare autosomal dominant defect, arose in a large family that had no prior history of the disease. Consider the following pedigree (the darkly colored symbols represent affected individuals): a. Circle the individual(s) in which the mutation most likely occurred. b. Is the person who is the source of the mutation affected by retinoblastoma? Justify your answer. c. Assuming that the mutant allele is fully penetrant, what is the chance that an affected individual will have an affected child?arrow_forwardExplain why familial breast cancer shows a dominant pattern of inheritance in a pedigree even though it is recessive at the cellular level.arrow_forward
- A woman knows that her mother is a carrier of Kartagener’s syndrome (an autosomal recessive disorder). The woman does not know if either she or her husband are carriers. The couple wants to have a child, but is worried about whether or not they could have a child with Kartagener’s syndrome. Should the couple seek the advice of a genetic counselor? In other words, is there a chance they could have an affected child? If there is a chance, please make sure your answer includes the specific parental genotypes necessary to make this possible.arrow_forwardFigure 1-15 shows the family tree, or pedigree, for LouiseBenge (Individual VI-1) who suffers from the diseaseACDC because she has two mutant copies of the CD73gene. She has four siblings (VI-2, VI-3, VI-4, and VI-5)who have this disease for the same reason. Do all of the10 children of Louise and her siblings have the samenumber of mutant copies of the CD73 gene, or mightthis number be different for some of the 10 children?arrow_forwardPrader-Willi Syndrome (PWS) is caused by a mutation in an autosomal gene that is maternally imprinted. If a male is affected with PWS, each of his sons has a ["100%", "75%", "50%", "25%", "0%"] chance of being affected with PWS, and each of his daughters has a ["50%", "75%", "25%", "0%", "100%"] chance of being affected with PWS. Pick answers within quotation marks to fill in blanks.arrow_forward
arrow_back_ios
SEE MORE QUESTIONS
arrow_forward_ios
Recommended textbooks for you
Human Heredity: Principles and Issues (MindTap Co...BiologyISBN:9781305251052Author:Michael CummingsPublisher:Cengage Learning
Biology Today and Tomorrow without Physiology (Mi...BiologyISBN:9781305117396Author:Cecie Starr, Christine Evers, Lisa StarrPublisher:Cengage Learning
Human Heredity: Principles and Issues (MindTap Co...
Biology
ISBN:9781305251052
Author:Michael Cummings
Publisher:Cengage Learning
Biology Today and Tomorrow without Physiology (Mi...
Biology
ISBN:9781305117396
Author:Cecie Starr, Christine Evers, Lisa Starr
Publisher:Cengage Learning
What are Mutations and what are the different types of Mutations?; Author: Science ABC;https://www.youtube.com/watch?v=I16YlE8qTBU;License: Standard youtube license