BackFor the retinal cancer retinoblastoma, the inheritance of one mutated copy of RB1 from one of the parents is often referred to as a mutation that produces a 'dominant predisposition to cancer.' This means that the first mutation does not produce cancer but makes it very likely that cancer will develop.
Using RB1⁺ for the normal wild-type allele and RB1⁻ for the mutant allele, identify the genotype of a cell in a retinoblastoma tumor.
An organism has alleles R₁ and R₂ on one pair of homologous chromosomes, and it has alleles T₁ and T₂ on another pair. Diagram these pairs of homologs at the end of metaphase I, the end of telophase I, and the end of telophase II, and show how meiosis in this organism produces gametes in expected Mendelian proportions. Assume no crossover between homologous chromosomes.
Figure 2.12 shows the results of Mendel's test-cross analysis of independent assortment. In this experiment, he first crossed pure-breeding round, yellow plants to pure-breeding wrinkled, green plants. The round yellow are crossed to pure-breeding wrinkled, green plants. Use chi-square analysis to show that Mendel's results do not differ significantly from those expected.
An experienced goldfish breeder receives two unusual male goldfish. One is black rather than gold, and the other has a single tail fin rather than a split tail fin. The breeder crosses the black male to a female that is gold. All the F₁ are gold. She also crosses the single-finned male to a female with a split tail fin. All the F₁ have a split tail fin. She then crosses the black male to F₁ gold females and, separately, crosses the single-finned male to F₁ split-finned females. The results of the crosses are shown below.
Black male x F₁ gold female:
Gold 32
Black 34
Single-finned male x F₁ split-finned female:
Split fin 41
Single fin 39
Is black color dominant or recessive? Explain. Is single tail dominant or recessive? Explain.
Cytoplasmic male sterility (CMS) in plants has been exploited to produce hybrid seeds (see Experimental Insight 17.1). Specific CMS alleles in the mitochondrial genome can be suppressed by specific dominant alleles in the nuclear genome, called Restorer of fertility alleles, RF. Consider the following cross:
♀CMS 1Rf 1/Rf1 rf2/rf2 × ♂CMS2rf 1/rf1 Rf2/Rf2
What genotypes and phenotypes do you expect in the F₁? If some of the F₁ plants are male fertile, what genotypes and phenotypes do you expect in the F₂?
Three strains of green-seeded lentil plants appear to have the same phenotype. The strains are designated G₁, G₂, and G₃. Each green-seeded strain is crossed to a pure-breeding yellow-seeded strain designated Y. The F₁ of each cross are yellow; however, self-fertilization of F₁ plants produces F₂ with different proportions of yellow- and green-seeded plants as shown below.
Using the allele symbols A and a, B and b, and D and d to represent alleles at segregating genes, give the genotypes of parental and F₁ plants in each cross.
Draw a pedigree containing two parents and four children. Both of the parents have AB blood type. The first child is type A, the second child is type AB, and the third child is type B.
The fourth child tests as having blood type O, which is not possible given the parental genotypes. Look at Figure 4.4 and read the description of the molecular process that generates ABO blood group antigens. What other mutation could account for this observation?
Draw a pedigree containing two parents and four children. Both of the parents have AB blood type. The first child is type A, the second child is type AB, and the third child is type B.
Assign the genotypes to these five people.
A pea plant that has the genotype RrGgwwdd is crossed to a plant that has the rrGgWwDd genotype. The R gene controls round versus wrinkled seed, the G gene controls yellow versus green seed, the W gene controls purple versus white flower, and the D gene controls tall versus short plants. Determine the following;
What proportion of the progeny are expected to be round, yellow, purple, and tall?
Go to the OMIM website (http://www.ncbi.nlm.nih.gov/omim) and locate the Search button at the top of the page. Use the Search function to look up, one by one, the following three human hereditary diseases that are relatively common in certain populations: 'Tay–Sachs disease' (select OMIM number 272800 from the search results list); 'cystic fibrosis' (select OMIM number 602421 from the search results list); and 'sickle cell anemia' (select OMIM 603903 from the search results list). For each of these diseases, look through the information and provide the following details:
In which population(s) does the disease most commonly occur?
Go to the OMIM website (http://www.ncbi.nlm.nih.gov/omim) and locate the Search button at the top of the page. Use the Search function to look up, one by one, the following three human hereditary diseases that are relatively common in certain populations: 'Tay–Sachs disease' (select OMIM number 272800 from the search results list); 'cystic fibrosis' (select OMIM number 602421 from the search results list); and 'sickle cell anemia' (select OMIM 603903 from the search results list). For each of these diseases, look through the information and provide the following details:
Briefly describe the disease.
Go to the OMIM website (http://www.ncbi.nlm.nih.gov/omim) and locate the Search button at the top of the page. Use the Search function to look up, one by one, the following three human hereditary diseases that are relatively common in certain populations: 'Tay–Sachs disease' (select OMIM number 272800 from the search results list); 'cystic fibrosis' (select OMIM number 602421 from the search results list); and 'sickle cell anemia' (select OMIM 603903 from the search results list). For each of these diseases, look through the information and provide the following details:
What gene is mutated in the disease?