Concept explainers
To describe: One observation in the human pedigree that rules out a recessive pattern of inheritance.
Introduction: Genetic disorder are caused due to abnormalities in the genome of a person and these disorders are inheritable from the parents to the offspring. Genetic disorders are of different types depending on the location of the infected genes and the type of allele on the chromosome such as autosomal dominant, autosomal recessive, X-linked dominant, X-linked recessive, Y-linked and mitochondrial disorders. For understanding the inheritance of human genetic diseases “pedigree analysis” is considered the most effective tool and it follows simple Mendelian pattern.
To describe: One observation in the human pedigree that rules out a dominant pattern of inheritance.
Introduction: The dominant and recessive pattern of inheritance is observed using the pedigree analysis. For a dominant pattern to be inherited only one of the dominant alleles need to be transferred but the recessive pattern of inheritance requires both the alleles that are transferred to be recessive.
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- For a recessive condition, two normal heterozygous individuals have children. What is the likelihood of their children being affected by this condition? What is the likelihood of their children being carriers without the condition? What is the likelihood of their asymptomatic children being carriers? Suppose that an individual with the condition has children with a heterozygous individual, what is the likelihood of their children being carriers?arrow_forwardIn humans, having extra fingers or toes is caused by a dominant allele (E). People with two recessive alleles have 5 fingers and toes on each hand or foot. What is the genotype of someone who has 5 fingers and toes on each hand or foot? What are the two different genotypes that someone with extra fingers or toes could have? If two people both had the normal number of fingers and toes, is there any chance that their children could inherit the allele for extra fingers and toes? Do a Punnett square and show your work. If a man who was heterozygous for this gene married someone who was homozygous for the recessive allele, what fraction of their children would you expect to have extra fingers or toes? Do a Punnett square and show your work.arrow_forwardA maternal effect can cause the offspring phenotype ratio to depart from that of classic Mendelian inheritance. In a species of snail, the dominant allele N codes for right-handed shell coiling and recessive allele n codes for left-handed shell coiling. If an Nn female with right-handed shell coiling mates with an Nn male, what is the shell coiling phenotypic ratio of their offspring? O 3, bidirectional coil : 1, left-handed coil 4, right-handed coil : 0, left-handed coil 3, right-handed coil: 1, left-handed coil 0, right-handed coil : 4, left-handed coilarrow_forward
- The following pedigree shows the 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. Using just the information on this pedigree, is Huntington’s disease caused by a dominant allele or recessive alleles? What are the genotypes of the grandparents (I-1 and I-2)? What are the genotypes of the parents (II-6 and II-7)? If the parents above have another child, what is the chance that they will be affected by the Hungtington’s disease allele? What are the genotypes of the unaffected children (III-8, 9, 10)? What is the chance that the unaffected children above will pass on a Huntington’s disease allele to their children? What is the genotype of the affected child (III-11)? What is the chance…arrow_forwardIn humans, brown eyes are dominant to blue eyes, and the ability to roll your tongue is dominant to not being able to roll your tongue. If a mother who was heterozygous for eye colour and homozygous recessive for tongue rolling had a baby with a father that was heterozygous for both traits, what is the probability that their child would have blue eyes and could roll their tongue?arrow_forwardDetermine the type of inheritance pattern shown in the pedigree below: Autosomal dominant Autosomal recessive Sex linked Mitochondrial A type of pattern we haven't learned (multiple alleles, polygenetic, etc.)arrow_forward
- Mendel's second postulate states: When two different unit factors responsible for a characteristic are found in the same organism, one will dominate and determine the characteristic type. Explain this postulate using modern genetic terms. Be sure to include the following terms in your explanation: dominant, recessive, allele, phenotype, genotype.arrow_forwardFor some traits, one allele is not completely dominant to another. Incomplete dominance occurs when neither allele dominates over the other. The resulting phenotype of heterozygotes is an intermediate of the two extremes. Incomplete dominant genes control snapdragon flower color. Red flower plants crossed with white flower plants produce offspring with pink flowers. One human trait that is thought to be inherited in this fashion is hair structure. Curly hair and straight hair are due to homozygous genotypes and wavy hair is produced by the heterozygous genotype. An incompletely dominant gene also controls the plumage of chickens. Black plumage and white plumage are due to homozygous genotypes and a blue-grey color results from a heterozygous genotype. Using Punnett squares and variations of the letter “B”, answer questions 1-3 and use variations of the letter “R” to answer questions 4-5. What type of offspring and in what ratio would you expect from a cross between a black…arrow_forwardAlbinism is the absence of pigment throughout the body. Animals with albinism have white fur and reddish eyes. Albinism is inherited as a recessive trait, so animals with two a alleles have albinism, whereas animals with at least one dominant A allele have normal coloring. Using the Punnett square below, determine the probability of two albino parents (with aa genotypes) producing a child with albinism.arrow_forward
- In Alaskan Malamute dogs, an autosomal recessive allele causes a condition in which the cartilage in the front legs fails to develop properly. This results in a type of dwarfism. Dogs with the dominant wild-type allele are of normal height. In the same breed of dogs, there is an autosomal dominant allele that codes for a curled tail and a recessive allele that codes for an uncurled tail. Show the possible genotypes for the offspring of a dog heterozygous for height and tail curl crossed with a dog recessive for both traits. Your answer must include the use of a Punnett square and a legend indicating the allele symbols used.arrow_forwardMendel's concept of dominance states that in a genotype where two different alleles of a locus are present, only the trait encoded by the dominant allele is observed. Give a molecular explanation for dominance, i.e. explain intracellular molecular events that can result in what we observe as dominance on a phenotypic level. Use the gene that encodes seed shape in peas as an example, where roun(R) is dominant over wrinkled(r), to explain how RR and Rr plants can have the same phenotype.arrow_forwardRed-green color blindness is inherited as an X-linked recessive (Xc). If a color-blind man marries a woman who is heterozygous for normal vision, what would be the expected phenotypes of their children with reference to this character? In your answer, specify in your phenotype descriptions the gender of the children. (For example, don’t just say 75% of the children would be colorblind – you would instead say 100 % of the daughters would be colorblind and 50% of the sons would be colorblind. Note that this is not a correct answer; it is just to give you an idea of how to explain the correct phenotypes of the cross.)___arrow_forward
- Human Biology (MindTap Course List)BiologyISBN:9781305112100Author:Cecie Starr, Beverly McMillanPublisher:Cengage Learning