Concept explainers
Achromatopsia is a rare autosomal recessive form of complete color blindness that affects about
Achromatopsia was first recorded on Pingelap in the
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Genetic Analysis: An Integrated Approach (2nd Edition)
- As discussed in the text, almost 5% of Caucasians carry a recessive gene for cystic fibrosis. Until recently, most people with cystic fibrosis died in childhood or early adulthood. Why is cystic fibrosis so frequent in spite of the fact that until recently it was usually lethal?arrow_forwardHeterozygote advantage is an interesting condition in those individuals who have one of each allele (dominant and recessive) have a higher survival rate than those individuals who are either homozygous dominant or homozygous recessive. Sickle-cell anemia is such a genetic disease associated with the recessive allele. Normal homozygous individuals (SS) have normal blood cells that are easily infected with the malarial parasite. Thus, many of these individuals become very ill from the parasite and many die. Individuals homozygous for the sickle-cell trait (ss) have red blood cells that readily collapse when deoxygenated. Although malaria cannot grow in these red blood cells, individuals often die because of the genetic defect. However, individuals with the heterozygous condition (Ss) have some sickling of red blood cells, but generally not enough to cause mortality. In addition, malaria cannot survive well within these "partially defective" red blood cells. Thus, heterozygotes tend to…arrow_forwardConsider a Droscophilia fly with a genotype of Nn XqYY. The dominant allele of the sex-linked gene specifies a black body and the recessive a white body. The recessive autosomal allele specifies hairy bristles while the dominant allele specifies smooth bristles. i)What is the ploidy of this fly? ii) What would the sex of this fly be? iii)What would the phenotype of this fly be with respect to these two loci?arrow_forward
- Cystic fibrosis (CF) is an autosomal recessive condition triggered by the overproduction of sticky mucus that clogs the lungs and pancreas. It is a life-threatening disease, but medical advances helped the afflicted to live through adulthood. Betty's mother died from cystic fibrosis, but her father was normal and never had any relative with CF. Her fiancé, Jones, turned out to be a carrier of the CF allele. What are the genotypes of Betty and Jones? 1. Betty: ________________________ 2. Jones: _____________________ They planned to have four children. What is the probability that: 3. all children will be normal 4. at least two will be normalarrow_forwardCystic fibrosis is an autosomal recessive disorder that affects 1 in 3 000 newborns with Caucasian background. It causes thick mucus build up in various organs and can cause damages and problems in respiratory and digestive systems. a) What is the frequency of the cystic fibrosis allele in the Caucasian population? Show all your work and express your answer as a value between 0 and 1 rounded to two decimal places. b) What percentage of the Caucasian population would be carriers for cystic fibrosis? Show all your work and express your answer rounded to two decimal places. c)If two individuals are carriers of the cystic fibrosis allele, what is the probability that they would have a girl without cystic fibrosis? Show all your work (including the Punnett square) and express your answer as a value between 0 and 1 rounded to two decimal places.arrow_forwardPolydactyly is an autosomal dominant trait that results in the presence of additional digits on the hands and feet. The incidence in Caucasians is approximately 1 in every 1300 births while in Africans and African Americans, the prevalence is 1 in every ~150 births. Fortunately, this trait does not cause any deleterious effects on one's health. Actually, there are a number of individuals who have been successful football players that were born with polydactyly. In 1902, a study found that the allele frequency of the recessive allele (p) was 30% in the local population. Last year, a follow-up study was published which assessed the genotypes of the same local population. The following data were obtained: pp = 10%; Pp = 40%; PP = 50% Use the above information to answer the questions below. Use the word bank for a subquestion when provided. What is the frequency of p (recessive allele) in the follow-up study? Round your answer to the nearest tenth. Did the population evolve?…arrow_forward
- Humans who are born homozygous for the recessive sickle cell allele die of sickle cell anemia, while those who are heterozygous are resistant to malaria. 5% of the population of the Congo are homozygous recessive for the sickle cell allele. What percentage of the population is resistant to malaria?arrow_forwardBelow in Figure 1 is a pedigree for a family afflicted by a genetic disorder. In some populations, Cystic fibrosis has an incidence of 1 in 2500 newborns. The carrier frequency calculated from this is 1/25. Analyze the pedigree below assuming the disease is similar to cystic fibrosis in incidence and carrier frequency. However this disease may not have the same type of genetic transmission as cystic fibrosis. What type of genetic transmission is most consistent with the pedigree? Label all the individuals that you can determine, with hypothesized genotypes. Label the individuals that have unknown genotypes with possible genotypes. Assuming her father is known to NOT be a carrier, calculate the probability that IV1 is a carrier for disease. Use the Χ2 test to determine whether your proposed transmission fits this data.arrow_forwardSickle cell anemia is caused by a recessive allele at a single gene. As we discussed in class, being a homozygote for the sickle cell allele is almost always lethal, but heterozygotes tend to be resistant against malaria although they have a mild form of anemia. Because of this heterozygote advantage, the allele for sickle cell anemia has a frequency of more than 10% in some human populations. How would present allele frequencies of the sickle cell allele change, if there was no heterozygote advantage or disadvantage (that is, that heterozygotes would be identical to ‘normal’ homozygotes – no malaria resistance, no anemia)? How would the change in sickle cell allele frequencies compare to scenario a (extirpation of malaria)arrow_forward
- In humans, the ability to smell hydrocyanic acid (HCN) is inherited as a recessive trait (h = can smell HCN, H = cannot smell HCN). A woman, a man, and their biological child are all standing in a room. The child can smell the HCN but the parents cannot. 1.) What is the genotype of the child? 2.) What are the possible phenotypes of the parents?arrow_forwardHereditary hemochromatosis is an autosomal recessive genetic disorder that causes the body to absorb too much iron from the diet. This excess iron is stored in the body's tissues and organs, particularly the skin, heart, liver, pancreas, and joints. Because humans cannot increase the excretion of iron, excess iron can overload and eventually damage tissues and organs. Some individuals who are homozygous for this autosomal recessive gene experience only skin discoloration and joint pain, others experience heart disease in addition to the skin discoloration, still other individuals suffer also suffer from diabetes, severe heart disease, and liver damage. Name and define this genetic phenomenon and explain how it relates to this specific genetic situation described above.arrow_forwardCystic fibrosis (CF) is an autosomal recessive trait. A three-generation pedigree is shown below for a family that carries the mutant allele for cystic fibrosis. Note that carriers are not colored in to allow you to figure out their genotypes. Normal allele = F CF mutant allele = f What is the genotype of individual #13? A) ff B) FF C) Ff D) it is impossible to tellarrow_forward
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