Concept explainers
Situs inversus is a congenital condition in which the major visceral organs are reversed from their nor-mal positions. Investigations into the genetics of this abnormality revealed that individuals with at least one dominant allele (SI) of an autosomal gene are normal but, surprisingly, of individuals that are homozygous for a recessive allele (si),
a. What genotypes and
b. What genotypes and phenotypes are expected in prog-eny from a cross of two SI si individuals?
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Genetic Analysis: An Integrated Approach (2nd Edition)
- 1. A) Apply the concept of sex linkage to explain why color blindness is more prevalent in men than in women. B) Mary is concerned that she may be a carrier for hemophilia, a sex-linked condition located on the X chromosome. Mary is married to John, who doesn't have hemophilia. Assuming Mary is a carrier, what are the genotype ratios expected for Mary and John's kids (specify for boys and for girls)? C) Mary and John have 2 boys, none of them has hemophilia. Can we use this fact as proof that Mary does not carry the allele for hemophilia? Explain your argument.arrow_forwardTuberous Sclerosis (TS) is an autosomal dominant genetic disease characterized by seizures, mental retardation, autism, and benign tumors of the brain, heart, skin, and kidneys. The kidney tumors can also be malignant. This disease exhibits a wide range of severity, and only about 1/3 of the cases are inherited. Two different genes have been tightly linked to the disease in families where it is inherited. The remaining 2/3 appear to be due to mutations in one of the 2 genes as well. Overall it appears that 1/2 are caused by mutations in TSC1 and the other half by mutations in TSC2. A rat model for hereditary renal carcinoma (kidney cancer) has been found. Southern and Northern blot analysis of the TSC1 and TSC2 gene revealed no differences between these rats and normal rats. Not all the rats in the strain would get cancer but a significant proportion did and those were selected for and used in experiments. 1. a) What was detected by the Southern blots? (look this up, make your…arrow_forwardy 301 Amelogenesis imperfecta is X-linked dominant. Affected XY individuals have extremely thin enamel on the teeth while XX carriers have grooved teeth from uneven deposition of enamel. If an unaffected XY individual were to produce children with a XX carrier partner, a. what would be the expected chance of a XY child being affected with the disease? b. what would be the expected chance of a XY child being affected with the disease?arrow_forward
- Examine the karyotypes of Jacob and PAtau syndromes. List the similarities and differences between these two syndromes. which is more severe?arrow_forwardAnhidrotic ectodermal dysplasia is an X-linked recessive disorder in humans characterized by small teeth, no sweat glands, and sparse body hair. This trait is usually seen in men, but women who are heterozygous carriers of the trait often have irregular patches of skin with few or no sweat glands (see the illustration below). a. Explain why women who are heterozygous carriers of a recessive gene for anhidrotic ectodermal dysplasia have irregular patches of skin lacking sweat glands. b. Why does the distribution of the patches of skin lacking sweat glands differ among the females depicted in the illustration, even between the identical twins?arrow_forward3) Achondroplasia is a common form of hereditary dwarfism that causes very short limbs, stubby hands, and an enlarged forehead. Below are three pedigrees depicting families with this specific type of dwarfism. A. What is the most likely mode of inheritance?arrow_forward
- Explain why disease alleles for cystic fibrosis (CF)are recessive to the normal alleles (CF+), yet thedisease alleles responsible for Huntington disease(HD) are dominant to the normal alleles (HD+).arrow_forwardColor blindness in humans is controlled by an X-linked completely recessive allele (Xc), while breast cancer is controlled by an autosomal completely dominant allele, B. A color blind male, who is a heterozygote carrier for breast cancer has three children/n with a normal eyed female (whose mother was color blind), who is homozygote recessive for the breast cancer allele. What is the probability that out of three children, 2 will be color blind males, and not show breast cancer, and one will be a color blind female, who shows breast cancer?arrow_forwardAlbinism, lack of pigmentation in humans, results from an autosomal recessive gene designated a. Two parents with normal pigmentation have an albino child. What is the probability that their next child will be albino? What is the probability that the next child will be an albino girl? If the child is normal, what is the probability that it will be a carrier (heterozygous) for the albino gene?arrow_forward
- The gene for polydactyly (P) is autosomal and dominant to normal fingers (p). Hemophilia is sex-linked and recessive (X h ). A man and his wife both of whom are polydactylous and have normal red blood cells have a child who is non-polydactylous and with hemophilia. What are their genotypes?arrow_forwarda)75% b)0% c)30%arrow_forwardA young lady requested pre-marital genetic counselling because her sister had died in infancy of gangliosidosis, an autosomal recessive disease. What is the risk that this young lady has similarly affected offspring? What advice should be given?arrow_forward
- Human Heredity: Principles and Issues (MindTap Co...BiologyISBN:9781305251052Author:Michael CummingsPublisher:Cengage Learning