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 (3rd Edition)
- There are two genes that determine the coat colour expression in some dogs: eumelanin and merle. These genes are located on two separate chromosomes. For the eumelanin gene, black coat colour (E) is dominant over red coat colour (e). The merle gene controls the degree to which these coat colours are expressed through incomplete dominance. The following table describes the merle gene expression. Genotype Phenotype MM White Mm Half colour (Grey or light red) mm Full colour (Black or Red) A grey dog that is heterozygous for the eumelanin gene mates with a light red dog. 1. What is the probability they would have a grey puppy? 2. What is the probability they would have a grey or light red puppy?arrow_forwardAPOE gene has been found to be a major contributor to sporadic Alzheimer's disease (AD), by acting as an age-of-onset modifier for the common relatively late-onset forms of the disease. Among four alleles causing early onset of AD, the epsilon4 allele (APOE4) disrupts this function. If you generate transgenic monkeys in which the normal allele of APOE gene is knocked out, what phenotype will you expect for those knockout monkeys? A. The APE mRNA expression will be completely suppressed. B. They slow down the development of AD. C. They develop AD early. D. They don't show any AD symptom.arrow_forwardIn squirrels, individuals that are heterozygous for the mutant LDL receptor gene( Fa) begin to experience heart attacks at the squirrel equivalent of the 30’s and 40’s in humans, while individuals that are homozygous for the mutant LDL receptor allele experience heart attacks much earlier. Closer examination reveals that the hepatocytes of the homozygous normal squirrels contain ONLY normal receptors. In the hepatocytes of the heterozygous squirrels, 50% of the receptors are of the mutant type, and fail to bind the LDL cholesterol, while the other 50% are normal. In individuals homozygous for the mutant LDL receptor allele, only mutant receptors are present. NAME and DEFINE the genetic phenomenon observed here.arrow_forward
- The drug tamoxifen has been used to treat some types of breast cancer. Suppose even among female patients with the same tumor grade there is variation in responsiveness to tamoxifen. It is also found that this variation is at least partly genetic; his variation is at least partly genetic; women with a relative who had a low responsiveness to the drug are at higher risk of low responsiveness to the drug The target of tamoxifen is a protein called the estrogen receptor. A. Outline how a “candidate gene approach” could be conducted to investigate whether variation in the gene for estrogen receptor affects tamoxifen responsivenessarrow_forwardThe genotype of a dwarf mouse is Igf2 Igf2–. What is the genotype of its father who has normal body size? Indicate which allele is on the maternal chromosome and which allele is on the paternal chromosome for both dwarf mouse and its father.arrow_forwardHuman females who are heterozygous for an X-linked recessive allele sometimes exhibit mild expression of the trait. However, such mild expression of X-linked traits in females who are heterozygous for Xlinked alleles is not seen in Drosophila. What might cause this difference in the expression of X-linked genes between human females and female Drosophila? (Hint: In Drosophila, dosage compensation is accomplished by doubling the activity of genes on the X chromosome of males.)arrow_forward
- Describe modifying epistasis. Modifying epistasis can be observed in the coat color of Dobermans. The doberman has two color genes: a black(B) and a color-dilution(D) gene. These two genes can create four different colors combinations in coat. Among the two color genes in the Doberman dogs, which one is the epistatic gene, and which one is the hypostatic gene. Why?arrow_forwardAlbinism is characterized by the lack of a dark pigment called melanin in the hair, skin and eyes. Albinism is caused by the absence of an functioning enzyme called thyrosinase, which is necessary for the synthesis of melanin. Given this bit of information, what can you assume about the heredity pattern of this trait? A) It is caused by a recessive allele of the gene coding for thyrosinase. B) It is caused by a dominant allele of the gene coding for melanin. C) It is caused by a dominant allele of the gene coding for thyrosinase. D) It is caused by a recessive allele of the gene coding for melanin. E) There is not enough information here to tellarrow_forwardSandhoff disease is due to a mutation in a gene that encodes a proteincalled hexosaminidase B. This disease has symptoms that aresimilar to those of Tay-Sachs disease. Weakness begins in the first 6 months of life. Individuals exhibit early blindness and progressive mental and motor deterioration. The family in the pedigree shown below has three members with Sandhoff disease, indicated with black symbols.arrow_forward
- Consider an autosomal recessive disease in which an individual must inherit two recessive alleles to display the disease phenotype. What is the probability that a woman who is a heterozygous for the trait and a man who is homozygous for the dominant allele will produce an offspring with the autosomal recessive phenotype? Assume no new mutations occur. Select one 1.) 100% 2.)25% 3.) 0% 4.)50% 5.) More information is neededarrow_forwardGenetic maternal effect is often seen in mammals. For example, research shows that the maternal genotype influences adult body size in mice. Why might these types of genetic effects be more common in mammals than in other organisms such as fishes, amphibians, or reptiles?arrow_forwardIn man, muscular dystrophy is a condition in which the muscles waste away during early life and may result in a shorter life expectancy. It is due to a sex-linked, recessive gene. A certain couple has five children – three boys (ages 1yr, 3yrs, and 10yrs old) and two girls (ages 5yrs and 7yrs old). The oldest boy shows the symptoms of this disease. You are their family physician and they come to you for advice. What would you tell them about the chances of their other children developing the disease?arrow_forward
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