Concept explainers
In certain cases, genetic testing can identify mutant alleles that greatly increase a person’s chance of developing a disease such as breast cancer or colon cancer. Between 50 and 70% of people with these particular mutations will develop cancer, but the rest will not. Imagine you are either a 30-year-old woman with a family history of breast cancer or a 30-year-old man with a family history of colon cancer (choose one). Each person can undergo genetic testing to identify a mutation that greatly increases susceptibility to the disease. Putting yourself in the place of the person you have chosen, provide answers to the following questions.
a. If you have a spouse or partner, are you obligated to tell that person the result of the genetic test? Why or why not?
b. If you have children, are you obligated to tell the children the result of the genetic test? Why or why not?
c. If you were the spouse or partner of the person you have selected, would you encourage or would you discourage the person from having the genetic test? Why?
d. If this person that you have selected were you, do you think you would have the genetic test or not? Can you explain the reasons for your answer?
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Genetic Analysis: An Integrated Approach (3rd Edition)
- A woman has her personal genome analyzed for the BRCA1 mutation after learning that her father is heterozygous and carries one mutant allele. What is her chance of inheriting the mutant allele from her father? 0: men cannot transmit genes affecting breast cancer. 25% 50% 75% 100% Among the progeny of a heterozygous round (Aa) x homozygous wrinkled ( aa) cross, three seeds are chosen at random. What is the probability that all three seeds are round? (1/4)3 1/4 (1/2) 3 1/2 A single gene can produce different proteins. True Falsearrow_forwardMany genetic counselors will not provide presymptomatic genetic testing for Huntington disease to people below the age of 18. Why are there concerns about offering this and many other genetic tests to minors? What types of presymptomatic genetic testing might be appropriate for minors?arrow_forwardSix months pregnant, an expectant mother had a routine ultrasound that showed that the limbs of the fetus were unusually short. Her physician suspected that the baby might have a genetic form of dwarfism called achondroplasia, an autosomal dominant trait occurring with a frequency of about 1 in 27,000 births. The parents were directed to a genetic counselor to discuss this diagnosis. In the conference, they learned that achondroplasia is caused by a mutant allele. Sometimes it is passed from one generation to another, but in 80 percent of all cases it is the result of a spontaneous mutation that arises in a gamete of one of the parents. They also learned that most children with achondroplasia have normal intelligence and a normal life span. 1. What information would be most relevant to concluding which of the two mutation origins, inherited or new, most likely pertains in this case? How does this conclusion impact on this couple’s decision to have more children? 2. It has been…arrow_forward
- A 20-year-old woman comes to your genetic counselling center because she knows that Huntington disease occurs in members of her family. Huntington is an autosomal dominant disease that often becomes apparent around 35–40 years of age. Her paternal grandfather was afflicted, but so far her 41 year old father shows no symptoms. Her two great-great grandmothers on her father's side were healthy well into their 90s, and one of her great-great grandfathers died of unknown causes at 45. Testing for Huntington disease is extremely expensive, but she is concerned that she may fall victim to this disease and wants to plan her life accordingly. After examining her pedigree you advise her to: not get tested because her father is only a carrier and it is very unlikely her mother is a carrier. not get tested because there is no possibility that she is homozygous. get tested because her father could be a carrier. not get tested because only males in her family get the disease. not get tested…arrow_forwardA RFLP is discovered that is linked to the gene for Duchenne’s muscular dystrophy (DMD). DMD is an X-linked, recessive trait. The RFLP is 2 map units from the gene for DMD. Consider the following pedigree and Southern blot using a probe that hybridizes to the RFLP. Which band/s is/are associated with DMD? What is the genotype for individuals 3 and 4? (Remember, this is an X linked disease, so use X’s and Y’s to denote). Individual 9 married a man who does NOT have muscular dystrophy, and she is pregnant. DMD is an X-linked trait. What is the probability for their child to have DMD? An amniocentesis is performed and it is determined that 9’s child in utero has only a 10 kb band that hybridizes to the same probe used above. What can you say about the child now?arrow_forwardA SNP marker is found linked to the cystic fibrosis gene. Cystic fibrosis is an autosomal recessive disease. A couple plans to have children together and both are carriers for the cystic fibrosis gene but do not have the disease themselves. They are both A1/A2 at the SNP and the A2 allele is linked with the allele causing cystic fibrosis. Assuming no crossing over between the SNP and the disease gene, what genotypes in the offspring could result that would cause cystic fibrosis? O A1-cf, A1 - cf O A2-cf, A2 - cf O A1 - CF, A1 - CF O A1 - CF, A2 - cfarrow_forward
- A child with the genes for PKU (a recessive disorder that leads to brain damage because proteins aren't digested properly) is raised to adulthood under a strict low-protein diet that prevents the gene from being activated. He lives a normal life and eventually becomes a father. As a genetic counselor, explain whether the fact that his gene is inactive affects the probability his future children might inherit the PKU allele. Be complete. Explain the reasoning you used to reach your conclusion. Display keyboard shortcuts for Rich Content Editorarrow_forwardBriefly discuss why mutant allele 1 fails to produce functional protein. (include three points in your answer)arrow_forwardDuchenne Muscular Dystrophy (DMD) is a disorder that primarily affects the function of skeletal muscles used for movement and cardiac muscles used for heart beating. Dystrophin is a protein encoded by a single gene, DMD, that is expressed in skeletal and cardiac muscle. Some forms of muscular dystrophy may be caused by different mutations in the DNA sequence of the DMD gene. Because the DMD locus is on the X chromosome, males are affected at higher rates. Two brothers, one of whom has DMD and one of whom does not, worked with their genetic counselor (Links to an external site.) to have their DMD gene sequenced to identify genetic variation that may explain why one brother was affected and the other not. Because DMD is a very long gene, a fictionalized, simplified model of the results is presented here (Figure 1). The actual DMD mRNA is about 16,000 base-pairs!------Consider single nucleotide polymorphism (SNP) #1 (Figure 1). Is this mutation likely to cause Duchenne muscular…arrow_forward
- Cystic fibrosis (CF) is an autosomal recessive trait. A three-generation pedigree is shown below for a family that carries the mutant allele for cystic fibrosis. Note that carriers are not colored in to allow you to figure out their genotypes. Normal allele = F CF mutant allele = f What is the genotype of individual #13? A) ff B) FF C) Ff D) it is impossible to tellarrow_forwardAn experimental assay for the blood-clotting protein called factorIX is available. A blood sample was obtained from each individual in the following pedigree. The amount of factor IX protein, shown within each symbol on the pedigree, is expressed as a percentage of the average amount observed in individuals who do not carry a mutant copy of the gene.arrow_forwardA defective gene on chromosome 15 causes Tay-Sachs disease. It is a central nervous system neurodegenerative disease that most often affects infants, though older children and adults can have late-onset forms of the disease. The defective gene prevents the body from making a protein called hexosaminidase A. Without, hexosaminidase A, chemicals called gangliosides build up in the nerve cells of the brain, destroying brain cells. Pedigree information regarding the incidence of Tay-Sachs within a family is depicted above. The row below that indicates the genotypes of individuals II-1, II-2, and III-1 is Select one: a. II-1 II-2 III-1 Aa Aa aa b. II-1 II-2 III-1 XAY XAXa XAXa c. II-1 II-2 III-1 XAY XAXA XaXa d. II-1 II-2 III-1 AA aa Aaarrow_forward
- Human Heredity: Principles and Issues (MindTap Co...BiologyISBN:9781305251052Author:Michael CummingsPublisher:Cengage Learning