Penile hypospadias, a birth defect in male humans in which the urethra opens on the shaft instead of at the tip of the penis, results from a dominant allele at an autosomal gene in some families. Females who carry the dominant allele show no effects. What type of trait is this birth defect an example of? a y linked trait because the defect occurs only in males a sex limited trait because the defect occurs only in males and the gene involved is autosomal a genetic maternal effect because the presence of the trait depends upon the genotype of the mother a sex influenced trait because the defect occurs only in males and the gene involved is autosomal an X linked trait because the defect occurs more often in males than in females

Penile hypospadias, a birth defect in male humans in which the urethra opens on the shaft instead of at the tip of the penis, results from a dominant allele at an autosomal gene in some families. Females who carry the dominant allele show no effects. What type of trait is this birth defect an example of? a y linked trait because the defect occurs only in males a sex limited trait because the defect occurs only in males and the gene involved is autosomal a genetic maternal effect because the presence of the trait depends upon the genotype of the mother a sex influenced trait because the defect occurs only in males and the gene involved is autosomal an X linked trait because the defect occurs more often in males than in females

Human Biology (MindTap Course List)

11th Edition

ISBN:9781305112100

Author:Cecie Starr, Beverly McMillan

Publisher:Cecie Starr, Beverly McMillan

Chapter19: Introduction To Genetics

Section: Chapter Questions

Problem 9CT

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Retinitis pigmentosa, a form of blindness in man, maybe caused either by a dominant autosomal gene R, or a recessive autosomal gene a. An afflicted man whose parents are both normal marries a woman with genotype AaRr. a. What proportion of the children are expected to suffer from this affliction if R and A are inherited independently? b. If this couple want to have normal children only, what isthe probability of having normal children?
In human beings, the gene for red‑green colorblindness (r) is sex‑linked and recessive to its allele for normal vision (R), while the gene for freckles (F) is autosomal and dominant over its allele for nonfreckled (f). A nonfreckled, normal‑visioned woman whose father was freckled and colorblind, marries a freckled, colorblind man whose mother was nonfreckled. What is the genotype of the woman's father? What is the probability that the couple's first child will be a non-freckled, normal visioned girl? What is the probability that the first two children born to the couple will be freckled and colorblind girls?
Huntington disease is a rare dominant condition in humans that results in a slow but inexorable deteriorationof the nervous system. The disease shows what mightbe called age-dependent penetrance, which is to saythat the probability that a person with the Huntingtongenotype will express the phenotype varies with age.Assume that 50% of those inheriting the HD allele willexpress the symptoms by age 40. Susan is a 35-yearold woman whose father has Huntington disease. Shecurrently shows no symptoms. What is the probabilitythat Susan will show symptoms in five years?
In individuals affected by cystic fibrosis, salt crystals may appear afterperspiration dries up. In addition, the disease causes respiratory disorderswhich can be both debilitating and lethal. It occurs in individuals homozygousfor recessive gene. If 2 normal parents had a daughter with the symptoms ofthis disease, and a normal son, what is the probability that he might be acarrier of the recessive gene?Express answer in fraction form.
.Certain forms of human color blindness are inherited as X-linkedrecessive traits. Hemizygous males are color-blind, but heterozygous females are not. However, heterozygous females sometimeshave partial color blindness.A. Discuss why heterozygous females may have partial color blindness.B. Doctors identified an unusual case in which a heterozygousfemale was color-blind in her right eye but had normal colorvision in her left eye. Explain how this might have occurred.
Piebald spotting is a condition found in humans inwhich there are patches of skin that lack pigmentation. The condition results from the inability ofpigment-producing cells to migrate properly duringdevelopment. Two adults with piebald spotting haveone child who has this trait and a second child withnormal skin pigmentation.a. Is the piebald spotting trait dominant or recessive?What information led you to this answer?b. What are the genotypes of the parents?
In a particular human family, John and his motherboth have brachydactyly (a rare autosomal dominant allele causing short fingers). John’s father hasHuntington disease (another rare autosomal dominant allele). John’s wife is phenotypically normaland is pregnant. Two-thirds of people who inheritthe Huntington (HD) allele show symptoms by age50, and John is 50 and has no symptoms.Brachydactyly is 90% penetrant.a. What are the genotypes of John’s parents?b. What are the possible genotypes for John? Howlikely is John to have each of these genotypes?c. What is the probability the child will express bothbrachydactyly and Huntington disease by age 50 ifthe two genes are unlinked?d. How will your answer to part (c) change if insteadthese two loci are 20 m.u. apart?
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