Concept explainers
Marcia saw an ad on television for ancestry DNA testing and thought, “Why not?” She ordered a kit, swabbed her inner cheek, and returned the kit for analysis. Several weeks later, she was surprised to learn that she was 17 percent Native American. An elderly great aunt confirmed that her mother’s family intermarried with members of Native American tribes in the Pacific Northwest in the early twentieth century. To investigate her maternal heritage, Marcia ordered a mitochondrial DNA (mtDNA) test, which confirmed her Native American ancestry. Based on these genetic results, she applied to several Native American tribes for enrollment as a tribal member. She was shocked when she was turned down. In discussions, tribal officials told her that DNA alone is not sufficient to define who is Native American. Tribal standards for enrollment vary, but usually cultural attributes such as knowledge of the language, customs, and history of the tribe are important considerations for enrollment decisions. Marcia was not satisfied and felt that she had a strong case based on biology alone. This series of events raises several questions:
How many great-grandmothers does any individual (such as Marcia) have? How many of them contribute to the mitochondrial DNA that an individual (Marcia) carries?
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Concepts of Genetics (12th Edition)
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- PKU is a recessive disorder based on a single mutant gene. Consider that Noor is a carrier, but her partner Hamza has never had an incidence of PKU show up in his family history, which dates back to four generations. What is the likelihood their first child might develop PKU according to their genetics counselor? a) 100%! b) 50% c) 25% d) 0%arrow_forwardCystic 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_forwardPhenylketonuria (PKU) is a human hereditary disease resulting from the inability of the body to process the chemical phenylalanine, which is contained in the protein we eat. PKU is manifest in early infancy and, if it remains untreated, generally leads to cognitive impairment. PKU is caused by a recessive allele with simple Mendelian inheritance. A couple intends to have children but consults a genetic counselor because the man has a sister with PKU and the woman has a brother with PKU. There are no other known cases in their families. They ask the genetic counselor to determine the probability that their first child will have PKU. What is this probability?arrow_forward
- The attached image is a pedigree of a family with a history of sickle cell anemia (the individuals with the filled-in symbols have the disease and no new mutations are occurring in any individual). Sickle cell anemia is inherited in an autosomal recessive manner. What is the probability that the individual with the question mark (?) will get the disease? a) 1/4 b) 1/2 c) 2/3 d) 1arrow_forwardBelow is a pedigree of a human genetic disease in which solid color indicates affected individuals. Assume that the disease is caused by a gene that can have the alleles A or a. a) Based on this pedigree, what is the most likely mode of inheritance? b) What is/are the possible genotype/s of person 1? c) What is/are the possible genotype (s) of person 4 ? Explain your answers.arrow_forwardPedigree analysis is often used to determine mode of inheritance (dominant or recessive, for example). Be sure to read the "Tips for Pedigree Analysis" in Figure 14.15 in 34. your text. Consider the following pedigree for the trait albinism (lack of skin pigmentation) in three generations of a family. (Solid symbols represent individuals with albinism.) Complete the unlabeled pedigree by indicating the genotypes for all involved. From your knowledge of Mendelian inheritance, answer the questions that follow. a. Is this trait caused by a dominant or recessive allele? What is the evidence for your response?arrow_forward
- If a Mother's genotype is IAi and her Daughter's genotype is ii and the mother claims a man who is type B as the father... a) Is that possible? Explain. b) The accused man can prove that both of his parents are type AB. Is it possible for him to be type B? If so, what is his genotype? Explain. d) Does the answer in part c change the answer in part b? Explain.arrow_forwardAlbinism is caused by an autosomal recessive allele that interferes with skin pigmentation in mammals. Two normally pigmented human parents already have an albino boy. They plan to continue to have children until they get a girl. Some or all of this information is important for each of the questions below. a) What is the probability that their next child (currently unborn) will be a girl with albinism? Explain your reasoning. b) What is the probability their first female child will be albino? Explain your reasoning. c) The answer to part (b) is different (and, yes, the answer is different) from the answer to part (a). Explain why. (Hint: it has something to do with the underlined words.)arrow_forwardAs a genetic counselor, you inform Susan and John that a blood test for cystic fibrosis is available. Would you recommend genetic testing for Susan and John? Explain.arrow_forward
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