Critical Thinking Questions – Biology A

Unit Three: Genetics

  1. Does a cell in metaphase II have the same mass of DNA as a diploid cell in the G1 phase of the cell cycle? Assume that both cells are from the same animal. Explain your answer.
  2. For a cell to function efficiently, the magnitude of its surface area must greatly exceed that of its volume. Explain how cell division functions to maintain this relationship between surface area and volume and in doing so maintains cell homeostasis.
  3. A cross between two pea plants with axial flowers and inflated pods gives the following offspring: 20 with axial flowers and inflated pods, 7 with axial flowers and constricted pods, and 5 with terminal flowers and inflated pods. What is the most probable genotype for the tow parents? Explain the results and show the Punnett square. How can the explanation be checked?
  4. Two black female mice are crossed with the same brown male mouse. Based on the information shown in the table below, answer the following questions:
  • What are the genotypes of each parent?
  • Which trait is dominant?
  • Is the dominance of the trait in (b) completely dominant, incompletely dominant, or codominant? Explain your answer.
  1. What would happen to the translation process if one nucleotide were not transcribed correctly? Present a minimum of three possibilities.
  2. How is a system composed of three bases per codon better suited to code for 20 amino acids than a system composed of two bases per codon?
  3. Genetic engineering involves inserting segments of DNA taken from one organism into the DNA of another organism. What would be the likely result of an experiment in which a scientist replaces a faulty stop codon in the DNA of mouse cells with the codon UAG taken from the DNA of a frog, a pine tree, or a clam? What do the results of this experiment suggest about the evolutionary ancestry of these organisms?
  4. A molecular biologist isolates mRNA from the brain and liver of a mouse and finds that the two types of mRNA are different. Can these results be correct, or has the biologist made an error? Explain your answer.
  5. Kwashiorkor is a disease in children caused by a diet high in carbohydrates but lacking in complete protein. When children with kwashiorkor are suddenly put on a diet rich in protein, they may become very ill with ammonia poisoning, and some even die. The high level of ammonia in their blood is due to the inadequate metabolism of protein. What does this tell you about the enzymes that metabolize protein?

Critical Thinking Questions – Biology A

Unit Three: Genetics

  1. Drosophilia feed on fermenting fruit, which often contains a large amount of alcohol. If Drosophilia are fed a diet that has high alcohol content, there is an increase in the amount of dehydrogenase, an enzyme that metabolizes alcohol, in the digestive tract. What does this increase tell you about the enzyme?
  2. Individuals who are heterozygous for sickle cell anemia generally have no symptoms of the disease. However, they should avoid extreme conditions that severely reduce the amount of oxygen available to the body, such as playing vigorous sports at high elevations. Explain why this would be advisable.
  3. The karyotypes of some Down syndrome individuals show that they have 46 chromosomes. However, close examination of these karyotypes reveals that three copies of chromosome 21 are indeed present in these individuals. Explain how a translocation can account for this rare form of Down syndrome.
  4. A 20 year-old man diagnosed with muscular dystrophy has a sister who is soon to be married. If you were the man, what would you tell your sister?