Concept explainers
Alleles of the IGF-1 gene in dogs, encoding insulin-like growth factor, largely determine whether a domestic dog will be large or small. Dogs with an ancestral domi-nant allele are large, whereas dogs homozygous for the mutant recessive allele are small. Chondrodysplasia, a short-legged phenotype (as in dachshunds and basset hounds), is caused by a dominant gain-of-function allele of the FGF4 gene. The MSTN gene encodes myostatin, a regulator of muscle development. Dogs with a dominant ancestral allele of the MTSN gene have normal muscle development, while dogs homozygous for recessive mutants in the MTSN gene are “double muscled” and have trouble running quickly. However, dogs heterozy-gous for the mutant allele run faster than either of the homozygotes. You breed a pure-breeding small basset hound ofnormal musculature with a pure-breeding “bully” whip-pet, a double-muscled large dog with normal legs.
a. What are the genotypes and
b. If the
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Genetic Analysis: An Integrated Approach (2nd Edition)
- List and describe at least two potential consequences to human health due to the paternal-age effect.arrow_forwarda. The ABO blood groups are controlled by the alleles of a single gene. A very rare example of epistasis is called the Bombay phenotype. If many couples with the genotypes IAIBHh x IAiHh have children, what ABO phenotypic ratio would you expect in their offspring? b. What genetic term (excluding epistasis) can be used to describe the expression of the ABO alleles in the presence of the hh genotype?arrow_forwardIn mice, the A allele causes agouti fur, the AY allele causes yellow fur and is dominant to the A allele. The homozygous AY AY genotype is lethal. Why is the AYAY homozygous condition lethal? The AY allele lacks an upstream merc gene which is required for normal embryonic development. The AY allele contains a null mutation in the A gene, which is required for normal embryonic development. The yellow pigment produced by A allele is required for survival. The AY allele highly transcribes the merc gene which is lethal in a homozygous AYAY individual. None of the other answers are correct.arrow_forward
- The following system models the exchange of nutrients between mother and fetus in the placenta: dC1/dx=−α1(C1−C2) dC2dx=−α2(C1−C2) where C1(x) is the concentration of nutrients in the maternal bloodstream at a distance x along the placental membrane and C2(x) is the concentration of nutrients in the fetal bloodstream at a distance x. Here, α1and α2 are constants and α1 ≠α2. If C1(0)=c0 and C2(0)=C0, use eigenvalues and eigenvectors to solve the system for C1(x) and C2(x). Please, answer all the steps and be careful with uppercase and lowercase C.arrow_forwardThe ABO blood groups in humans are expressed as the IA, IB, and i alleles. The IA allele encodes the A blood group antigen, IB encodes B, and i encodes O. Both A and B are dominant to O. If a heterozygous blood type A parent (IAi) and a heterozygous blood type B parent (IBi) mate, one quarter of their offspring will have AB blood type (IAIB) in which both antigens are expressed equally. Therefore, ABO blood groups are an example of: a. multiple alleles and incomplete dominance b. codominance and incomplete dominance c. incomplete dominance only d. multiple alleles and codominancearrow_forwardSix 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_forward
- A couple who are both heterozygous for an autosomal recessive mutation that is narrowly expressed and fully penetrant are planning on having three children. What is the probability that one their children will be normal (unaffected) and two children will have the recessive mutant phenotype? Show your work. Please answer this question using the Bayes’ Theoremarrow_forwardPropose a hypotheses for this observation: In a study conducted by an undergraduate student, he obtained data showing that approximately 75% of the European Northern human population demonstrate the expression of a phenotype directly associated with the homozygous dominant genotype, while 25% display the mutant phenotype despite their genotypes being homozygous dominant.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_forward
- One particularly useful feature of the Hardy-Weinberg equation is that it allows us to estimate the frequency of heterozygotes for recessive genetic diseases, assuming that Hardy-Weinberg equilibrium exists. As an example, let’s consider cystic fibrosis, which is a human genetic disease involving a gene that encodes a chloride transporter. Persons with this disorder have an irregularity in salt and water balance. One of the symptoms is thick mucus in the lungs that can contribute to repeated lung infections. In populations of Northern European descent, the frequency of affected individuals is approximately 1 in 2500. Because this is a recessive disorder, affected individuals are homozygotes. Assuming that the population is in Hardy-Weinberg equilibrium, what is the frequency of individuals who are heterozygous carriers?arrow_forwardThe dosage of X chromosome expression is equalized between male and female mammals. Think about the example of calico cats to answer the following questions. Use Xb to represent the allele for black fur, XB to represent the allele for orange fur. What genotype(s) of female cats is/are expected to have a calico coat? Is it possible to have a calico cat that is male? Explain.arrow_forwardWhich of the following findings supports the fact that the presence of the Y-chromosome rather than the lack of a second X-chromosome determines the development of maleness in mammals? a. A human with an X0 genotype (Turner syndrome) is phenotypically female. b. A human with an XXY genotype (Klinefelter syndrome) is phenotypically male. c. A transgenic mouse with two X-chromosomes and the SRY gene from the Y-chromosome develops male sex organs. d. b and c, but not a e. a, b, and carrow_forward
- Human Biology (MindTap Course List)BiologyISBN:9781305112100Author:Cecie Starr, Beverly McMillanPublisher:Cengage Learning