Concept explainers
To analyze:
The following, based on the given pedigree of congenital cataracts in the humans,
1. Whether the cataracts are inherited as the autosomal recessive or the dominant trait.
2. The chance that the person 5 in the second generation, would produce a girl with cataract.
Given:
The following pedigree chart represents the inheritance of congenital cataracts, which is a rare mutant
Figure 1: A pedigree chart representing the inheritance of cataract in humans.
Introduction:
The chromosomes other than the sex-chromosomes are called as autosomes. They do not participate in the determination of sex. The disorders of autosomes affect the male and female progeny alike. The results of offsprings are not biased between male and female. These autosomal disorders can be recessive or dominant. When the presence of one affected allele results in a diseased condition, the trait is autosomal dominant. The case where both the alleles are required to express a diseased condition, then those alleles are called as autosomal recessive alleles.
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Chapter 12 Solutions
Life: The Science of Biology
- A couple was referred for genetic counseling because they wanted to know the chances of having a child with dwarfism. Both the man and the woman had achondroplasia (MIM 100800), the most common form of short-limbed dwarfism. The couple knew that this condition is inherited as an autosomal dominant trait, but they were unsure what kind of physical manifestations a child would have if it inherited both mutant alleles. They were each heterozygous for the FGFR3 (MIM 134934) allele that causes achondroplasia. Normally, the protein encoded by this gene interacts with growth factors outside the cell and receives signals that control growth and development. In achrodroplasia, a mutation alters the activity of the receptor, resulting in a characteristic form of dwarfism. Because both the normal and mutant forms of the FGFR3 protein act before birth, no treatment for achrondroplasia is available. The parents each carry one normal allele and one mutant allele of FGRF3, and they wanted information on their chances of having a homozygous child. The counsellor briefly reviewed the phenotypic features of individuals with achondroplasia. These include facial features (large head with prominent forehead; small, flat nasal bridge; and prominent jaw), very short stature, and shortening of the arms and legs. Physical examination and skeletal X-ray films are used to diagnose this condition. Final adult height is approximately 4 feet. Because achondroplasia is an autosomal dominant condition, a heterozygote has a 1-in-2, or 50%, chance of passing this trait to his or her offspring. However, about 75% of those with achondroplasia have parents of average size who do not carry the mutant allele. In these cases, achondroplasia is due to a new mutation. In the couple being counseled, each individual is heterozygous, and they are at risk for having a homozygous child with two copies of the mutated gene. Infants with homozygous achondroplasia are either stillborn or die shortly after birth. The counselor recommended prenatal diagnosis via ultrasounds at various stages of development. In addition, a DNA test is available to detect the homozygous condition prenatally. What if the couple wanted prenatal testing so that a normal fetus could be aborted?arrow_forwardA couple was referred for genetic counseling because they wanted to know the chances of having a child with dwarfism. Both the man and the woman had achondroplasia (MIM 100800), the most common form of short-limbed dwarfism. The couple knew that this condition is inherited as an autosomal dominant trait, but they were unsure what kind of physical manifestations a child would have if it inherited both mutant alleles. They were each heterozygous for the FGFR3 (MIM 134934) allele that causes achondroplasia. Normally, the protein encoded by this gene interacts with growth factors outside the cell and receives signals that control growth and development. In achrodroplasia, a mutation alters the activity of the receptor, resulting in a characteristic form of dwarfism. Because both the normal and mutant forms of the FGFR3 protein act before birth, no treatment for achrondroplasia is available. The parents each carry one normal allele and one mutant allele of FGRF3, and they wanted information on their chances of having a homozygous child. The counsellor briefly reviewed the phenotypic features of individuals with achondroplasia. These include facial features (large head with prominent forehead; small, flat nasal bridge; and prominent jaw), very short stature, and shortening of the arms and legs. Physical examination and skeletal X-ray films are used to diagnose this condition. Final adult height is approximately 4 feet. Because achondroplasia is an autosomal dominant condition, a heterozygote has a 1-in-2, or 50%, chance of passing this trait to his or her offspring. However, about 75% of those with achondroplasia have parents of average size who do not carry the mutant allele. In these cases, achondroplasia is due to a new mutation. In the couple being counseled, each individual is heterozygous, and they are at risk for having a homozygous child with two copies of the mutated gene. Infants with homozygous achondroplasia are either stillborn or die shortly after birth. The counselor recommended prenatal diagnosis via ultrasounds at various stages of development. In addition, a DNA test is available to detect the homozygous condition prenatally. Should the parents be concerned about the heterozygous condition as well as the homozygous mutant condition?arrow_forwardA man is brachydactylous (very short fingers; rare autosomal dominant), and his wife is not. Both can taste thechemical phenylthiocarbamide (autosomal dominant;common allele), but their mothers could not.a. Give the genotypes of the couple.If the genes assort independently and the couple hasfour children, what is the probability ofb. all of them being brachydactylous?c. none being brachydactylous?d. all of them being tasters?e. all of them being nontasters?f. all of them being brachydactylous tasters?g. none being brachydactylous tasters?h. at least one being a brachydactylous taster?arrow_forward
- In 1995, doctors reported a Chinese family in whichretinitis pigmentosa (progressive degeneration of theretina leading to blindness) affected only males. Allsix sons of affected males were affected, but all of thefive daughters of affected males (and all of thechildren of these daughters) were unaffected.a. What is the likelihood that this form of retinitispigmentosa is due to an autosomal mutationshowing complete dominance?b. What other possibilities could explain the inheritance of retinitis pigmentosa in this family? Whichof these possibilities do you think is most likely?arrow_forwardIn the human pedigree shown below, black filled symbols indicate individuals suffering from a rare genetic disease, whereas empty symbols represent people who do not have the disease. Based on the pedigree, what is the most likely mode of inheritance of this rare genetic disease? O Y-linked OX-linked dominant Autosomal recessive O Autosomal dominant OX-linked recessivearrow_forwardHemophilia is a disease inherited as a X-linked recessive trait while pattern baldness is controlled by an autosomal gene that is dominant in males and recessive in females. A hemophilic man who is also homozygous for baldness has children with a woman who carries normal genes for both traits. What is the probability that any of their child will be: a. Hemophilic, normal-haired male b. Hemophilic, bald male c Female with normal blood clotting and bald Note: Show how you derived your answers.arrow_forward
- Duchenne muscular dystrophy is sex linked and usuallyaffects only males. Victims of the disease become progressively weaker, starting early in life.a. What is the probability that a woman whose brotherhas Duchenne’s disease will have an affected child?b. If your mother’s brother (your uncle) had Duchenne’sdisease, what is the probability that you have receivedthe allele?c. If your father’s brother had the disease, what is theprobability that you have received the allele?arrow_forwardRefer to the pedigree below which shows inheritance for achondroplasia (dwarfism), a dominantly inherited trait (denoted as D), which are the darkened circles and squares. Dwarfism (darkened shapes) are dominantly inherited, while normal height is recessively inherited (hh). Based on the pedigree, what is the correct genotype for individual #II-6? Dominant Autosomal Pedigree 2 II 2 3 II 1 2 3 6 9 10 Dd DD DD or Dd ddarrow_forward15. The following pedigree shows inheritance of Huntington's disease, a fatal genetic disorder that causes neurodegeneration. Since signs and symptoms usually do not appear until adulthood, many who are carriers may not realize their risk of passing on the disease-causing allele. The following pedigree represents a family in which some people are affected by Huntington's disease. Reeessive Trit er btmnt be Mec yplicalty Hinheteearrow_forward
- Sickle cell anemia is an inherited red blood cell disorder in which there are not enough healthy red blood cells to carry oxygen throughout the body. The allele that causes sickle-cell anemia is autosomal recessive (s), and the dominant allele can be represented by S. How many offspring will be affected by the disorder if the mother is a carrier, and the father appears to be normal? (Include the gender) a. b. How many will become carriers? (include the gender) A- 三三三 四 四 II !!arrow_forwardHolstein cattle suffers from the condition citrullinemia in which homozygus recessive calves die within a week of birth bc they can not break down ammonia that is produced when amino acids are metabolized. If a cow that is heterozygous for the citrullinemia gene is inseminated by a bull that is homozygous dominant, ehat is the probability that a calf inherits citrullinemia ( autosomal recessive)arrow_forward3) You have sought a job at a human genetic counseling clinic. They gave you an aptitude test shown below. Answer the yes/no questions concerning each of the following pedigrees. Pedigree A: YES or NO Could this trait be inherited as a simple autosomal recessive? Could this trait be inherited as a simple autosomal dominant? Could this trait be inherited as a simple X-linked recessive? Could this trait be inherited as a simple X-linked dominant? Pedigree B: YES or NO Could this trait be inherited as a simple autosomal recessive? Could this trait be inherited as a simple autosomal dominant? Could this trait be inherited as a simple X-linked recessive? Could this trait be inherited as a simple X-linked dominant?arrow_forward
- Human Heredity: Principles and Issues (MindTap Co...BiologyISBN:9781305251052Author:Michael CummingsPublisher:Cengage Learning