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)
- Suppose a geneticist is using a three-point test cross to map three linked rabbit morphology and behavioral mutations called si, It, and Le. The gene si is associated with the silky fur phenotype, and It is associated with the long-tailed phenotype. Both si and It are recessive mutations with respect to wild type. Le is a dominant mutation that confers the lethargic phenotype. The geneticist first crosses true-breeding lethargic rabbits to true-breeding silky fur, long-tailed rabbits. Next, the geneticist backcrosses the Fj progeny to the silky fur, long-tailed parents, and obtains the results reported in the table. Phenotype Number lethargic 815 silky fur, long-tailed 807 long-tailed 177 silky fur, lethargic 179 silky fur 7 long-tailed, lethargic 5 silky fur, long-tailed, lethargic 29 wild type 29 Place the genes in the correct order in the chromosome. Answer Bank si It Learrow_forwardIn the fish Species a, the expression of different combinations of four Hox genes results in structural differences in tissues and organs along the anterior-posterior axis. Figure 3 shows the expression pattern of four genes, i.e. Genes 1 – 4, and the tissue produced along the embryonic anterior - posterior plane of fish Species a wild type. The influence of Hox genes on the formation of specific types of tissue can be determined by introducing gain-of-function and loss-of-function mutations in specific Hox genes. Looking at Figure 3, predict what would happen to each one of the four types of tissues, if the expression of gene 3 was expanded anteriorly by a gain-of-function mutation so that the pattern of gene 3 expression would be the same as that of gene 2.arrow_forwardThere 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_forward
- In 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_forwardSex determination is primarily governed by either the male heterogamety of XX/XY type or female heterogamety of ZW/ZZ type with a seemingly one-to-one sex ratio of males to females. Many breeders of mammals would prefer a bias though towards a greater proportion of females to males due to males being overall less productive to females. What benefit is there is having a relatively equal proportion of male to female offspring when, in production terms, this is less then desirable?arrow_forwardDescribe 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_forward
- At least two pairs of genes control eye color. Both pairs influence the production of the pigment, melanin, but act independently. One pair of alleles is B (Brown color; dominant) and b (blue color); the other pair is A (pigment production; dominant) and a (no pigment production; albino). The gene pair aais epistatic to (masks) B and b and produces the nonpigmented eyes of the albino. What is the typeof gene interaction that exists between the two gene pairs? Give the genotypes and phenotypes of the possible offspring of the mating bbAa x Bbaa andi ndicate the parental phenotypes. (any method)arrow_forwardConsider 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_forward
- Sickle cell anemia is a genetically inherited autosomal recessive trait in which results in a condition that there are not enough healthy red blood cells to carry oxygen throughout the body due to the production of red blood cells that are sickle shaped. The frequency of the sickle cell condition is as high as 10% in Central Africa compared to 0.5% in the United States. Calculate the frequency of the normal and carries of the sickle cell condition.arrow_forwardAssume that a single gene determines coat coloration in cats, with the B allele resulting in orange coloration, and b allele results in black coloration. This gene exists on the X chromosome (recall that cats have XX/XY system of sex determination). My cat Pepper is a female tortoiseshell, and my cat Hobbes is an orange male. (i) What is the probability that Hobbes and Pepper have three kittens, Hopper (male), Pepsi (female), and Hippie (female)? What is the probability that they have three kittens, and that Hopper (male), and Hippie (female) are both orange, and that Pepsi (female) is a tortoiseshell? (ii) Distribution of % of Barr Bodies in each body part 120 100 100 80 100 60 40 50 50 20 Head Body Tail Black Orangearrow_forwardTwo brown bears have cubs in late spring. The mother bear has the phenotype for long front claws. The mother bear has the genotype (Aa), while the father has the same genotype as the mother. A) What percentage of the offspring will have long claws?arrow_forward
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