Concept explainers
To review:
Whether the following examples are description of genetics at the molecular, cellular, organism or population level.
A. The HbS allele encodes a polypeptide that functions slightly differently from the polypeptide encoded by the HbA allele.
B. If an individual has two copies of the Hbs allele, that person’s red blood cells take on a sickle shape.
C. Individuals who have two copies of the HbA allele do not have sickle cell disease, but they are not resistant to malaria. People who have one HbA allele and one HbS allele do not have sickle cell disease and are resistant to malaria. People who have two copies of the HbS allele have sickle cell disease and this disease may significantly shorten their lives.
D. Individuals with sickle cell disease have anemia because their red blood cells are destroyed by the body.
Introduction:
The blood disease called sickle cell anemia is a heritable disease. The affected individuals do not have enough oxygen-carrying hemoglobin in their blood, which causes the red blood cells (RBCs) to shrink and acquire a sickle shape. This happens due to the defective β–globin gene.
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Chapter 1 Solutions
Genetics: Analysis and Principles
- In a study of a muscle disorder, several affected families exhibited vision problems, muscle weakness, and deafness (M. Zeviani et al. 1990. American Journal of Human Genetics 47:904–914). Analysis of the mtDNA from affected members of these families revealed that large numbers of their mtDNA molecules possessed deletions of varying lengths. Different members of the same family and even different mitochondria from the same person possessed deletions of different sizes, so the underlying defect appeared to be a tendency for the mtDNA of affected persons to have deletions. A pedigree of one of the families studied is shown below. The researchers concluded that this disorder is inherited as an autosomal dominant trait, and they mapped the diseasecausing gene to a position on chromosome 10 in the nucleus. Q. What characteristics of the pedigree rule out inheritance of a trait encoded by a gene in the mtDNA as the cause of this disorder?arrow_forwardIn a study of a muscle disorder, several affected families exhibited vision problems, muscle weakness, and deafness (M. Zeviani et al. 1990. American Journal of Human Genetics 47:904–914). Analysis of the mtDNA from affected members of these families revealed that large numbers of their mtDNA molecules possessed deletions of varying lengths. Different members of the same family and even different mitochondria from the same person possessed deletions of different sizes, so the underlying defect appeared to be a tendency for the mtDNA of affected persons to have deletions. A pedigree of one of the families studied is shown below. The researchers concluded that this disorder is inherited as an autosomal dominant trait, and they mapped the diseasecausing gene to a position on chromosome 10 in the nucleus. Q. Explain how a mutation in a nuclear gene might lead to deletions in mtDNA.arrow_forwardThe young woman shown at right has albinismvery pale skin, white hair, and pale blue eyes. This phenotype is due to the absence of melanin, which imparts color to the skin, hair, and eyes. It typically is caused by a recessive allele. In the following situations, what are the probable genotypes of the father, the mother, and their children? a. Both parents have normal phenotypes; some of their children are albino and others are not. b. Both parents and all their children are albino. c. The mother is not albino, the father is albino, and one of their four children is albino.arrow_forward
- Phenylketonuria (PKU) is an inherited disease caused by a recessive allele. Individuals with PKU have two recessive alleles and have very low levels of an enzyme that is needed to properly break down proteins. If a woman and her husband are both carriers and have three children, what is the probability of each of the following? Show your math. (Hint: You can represent your probabilities as fractions or decimals, but probabilities are always between 0 and 1) a. All three children are of normal phenotype. b. One or more of the three children have the disease. c.All three children have the disease.arrow_forwardTay Sachs is a rare autosomal recessive disorder that causes mental and physical disabilities leading to death in infants. Affected individuals are lacking the enzyme hexosaminidase, causing lipids to build up in the brain.The HEXA gene on chromosome 15 codes for hexosaminidase, and a four base pair insertion in the gene results in an altered reading frame and non-functional enzyme being produced. Individuals who are carriers (heterozygotes) of the Tay-Sachs allele are not affected by the disease but appear to have increased protection against tuberculosis.The incidence of Tay-Sachs disease is much higher among Ashkenazi Jews originating from Eastern Europe than the general population of the United States. About 1 in 3 500 babies of Ashkenazi Jewish heritage are born with Tay-Sachs disease and about 1 in 30 Ashkenazi Jews are carriers compared to about 1 in 320 000 babies born with the disease and about 1 in 300 carriers in the general United States population. Ashkenazi Jews living in…arrow_forwardTake the example of B-thalassemia, an autosomal recessive genetic disease that particularly affects people from around the Mediterranean. This disease is associated with an anomaly of hemoglobin, a protein essential for the transport of oxygen, which is composed of four chains: two alpha (a) and two beta (B). In case of B-thalassemia, the ẞ chains are produced in insufficient or no quantity in an individual homozygous recessive resulting in insufficient production of overall hemoglobin leading to anemia and other physiological challenges. The gene that controls the synthesis of the ẞ chains is located on chromosome 11. Here is part of the coding portion of this gene (which controls a total of 146 amino acids and of which you only see the portion 36 to 41) and one of the targeted mutations: 1. Give the sequence of amino acids from the template and mutated strands. 2. What type of point mutation is it? 3. Using the principles of the theory of evolution, explain briefly and generally why…arrow_forward
- The use of nucleotide sequence data to measure genetic variability is complicated by the fact that the genes of higher eukaryotes are complex in organization and contain 5′ and 3′ flanking regions as well as introns. Researchers have compared the nucleotide sequence of two cloned alleles of the g-globin gene from a single individual and found a variation of 1 percent. Those differences include 13 substitutions of one nucleotide for another and 3 short DNA segments that have been inserted in one allele or deleted in the other. None of the changes takes place in the gene’s exons (coding regions). Why do you think this is so, and should it change our concept of genetic variation?arrow_forwardIn a particular country in sub-Saharan Africa, a medical study revealed that 0.075% of the country's population are suffering from sickle-cell anemia. Sickle cell disease is caused by a mutation in the haemoglobin-Beta gene found on chromosome 11. Sickle cell anemia is controlled by a pair of alleles, H and h, where the individuals with the illness have the homozygous recessive genotype; those with normal red blood cells have the alternative genotype. Using the Hardy-Weinberg's equation, calculate the percentage of the population of the two genotypes for normal blood cells. In a few remote areas in that country, the percentage of sickle cell anemia reaches as high as 5%. Calculate the percentage of homozygous and heterozygous individuals with the normal blood cells and find the ratio for both phenotypes.arrow_forwardSickle cell anemia is a genetic disease most common in those of African ancestry that results from the mutation of a single basepair. This mutation results in a change to the hemoglobin protein. In this experiment, “S” will represent the normal allele and “s” thesickle allele. They are codominant alleles. Therefore, SS is normal, Ss is not fatal but mildly symptomatic, and ss is debilitating,painful, and often fatal. After hundreds or even thousands of generations, both alleles are still common in those of African ancestry. How would you explain this?arrow_forward
- Six single-nucleotide polymorphism (SNP) loci are known to contribute to the development of type 2 diabetes. Diabetes is certain if eight or more of the alleles at these six loci are of the “contributing” variety. An uppercase letter indicates an allele that contributes to diabetes and a lowercase symbol indicates a noncontributing allele. A married couple wants to know the probability of producing a child who is at severe risk of type 2 diabetes. Their genotypes were determined by microarray analysis and are as follows: AaBbccDDEEFf × AaBbCCDdEeFfarrow_forwardDNA sequencing of your own two β-globin genes (one from each of your two Chromosome 11s) reveals a mutation in one of the genes. given this information alone, should you worry about being a carrier of an inherited disease that could be passed on to your children? What other information would you like to have to assess your risk?arrow_forwardIn humans the allele coding for normal metabolism of the amino acid phenylalanine (P) is dominant over the recessive autosomal allele (p) that causes the disease phenylketonuria, or PKU. Without treatment, this disease is characterized by brain damage due to the failure of the gene to code correctly for the enzyme phenylalanine hydroxylase. If a man marries a woman and both are heterozygous for hemophilia and heterozygous for PKU, what is the chance that they will have a child afflicted by both diseases? Your response MUST include:(a): list the traits involved (example: Color: Blue- B (dominate) Green - b (recessive) -Do not use this example as this is not part of the problem(b): identify if its a monohybrid or dihybrid cross and why (use prompt above) (c): create a punnet square that represents the problem abovearrow_forward
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