Problem Set 3 Meiosis and Genetics
17. In a particular breed of dog, the dominant allele B produces black coat color, while b produces brown.
a. If a litter of puppies has both black and brown offspring, what are the possible genotypes of the parents?
b. If a black and brown dog can produce black and brown puppies when they mate, what should be the ratio of black puppies to brown puppies in a litter?
18. Tongue rolling is a dominant trait in humans (T), while the inability to tongue roll is recessive. A woman who can roll her tongue marries a man who cannot. Their first child is also not a tongue roller.
a. What are the phenotypes of each parent, and the first child?
b. What is the probability that their second child will be a tongue roller?
c. A non-tongue roller?
19. In a test cross with the following pea plant (Gg Tt RR Ss), where genes show independent assortment:
a. What is the expected frequency of gg tt Rr ss progeny?
b. What is the expected frequency of progeny that are heterozygous for all of the genes?
20. Color blindness is a recessive, sex-linked trait. A color blind woman has a normal mother.
a. What is the genotype of the color blind woman’s father?
b. The color blind woman marries a normal man. What is the probability that their sons will be colorblind?
c. What is the probability that their daughters will be colorblind?
21. Use the following pedigree to determine the probability that IV-1 (child yet to be
22. Assuming the following pedigrees, is the trait autosomal or sex-linked, and dominant or reces
23. Incomplete dominance _________.
a. Is the presences of three or more alleles of a gene among individuals of a population
b. Causes heterozygous offspring to have an phenotype that is intermediate between the two parental phenotypes
c. Is when two genes at different loci both affect the same phenotype
d. Causes there to be a lack of production of heterozygous offspring
Use the following information to answer questions 24-25:
Duchenne Muscular Dystrophy (DMD) is an X-linked recessive disorder that causes an individual’s muscles to degenerate over time. A male DMD patient has two unaffected parents.
24. Fill in the pedigree of this family using Xd for the Duchenne allele, XD for the “normal” allele, X? for any unknown X alleles , and Y for Y chromosomes.
25. It turns out the son with DMD also has Klinefelter syndrome. What nondisjunction event would account for both disorders?
a. NDJ in Meiosis I of father
b. NDJ is Meiosis II of father
c. NDJ in Meiosis I of mother
d. NDJ is Meiosis II of mother
26. You’re a genetic counselor. A mother and father both with type AB blood have a child with blood type O. A second type-O child was born six years later. The father is upset and worried that, perhaps, he is not the biological father. After extensive genotyping, you determine that he is most likely the father of both children. This is an example of the “Bombay phenotype”. A separate locus codes for a precursor to the A & B antigens (the H antigen). If the child is hh, no H antigen is made and the child will be phenotypically type O. What is the name of the genetic phenomenon that accounts for the Bombay phenotype?
27. Achondroplasia is an autosomal dominant form of dwarfism. People with achondroplasia are heterozygotes because carrying two copies of the dominant, mutant allele is fatal during embryogenesis. Two people with achondroplasia decide to start a family.
a. Fill out a Punnett square for this couple.
b. What is the probability that their first child born will be of average stature?
c. What is the probability that this couple has two daughters with achondroplasia and one son of average stature in that order?
d. What is the probability that this couple has two children with achondroplasia and one of average stature in any order?
28. Two deaf people have three children together, none of whom are deaf. What is the name for the genetic phenomenon that makes this possible?
29. Individuals that inherit a single inactive retinoblastoma (Rb) allele from one of their parents have a 90% chance of developing multiple eye tumors as a child. The allele can be inherited from either the mother or father and affect both male and female children equally.
a. Based on this information alone, what is the mode of inheritance?
b. As it turns out, the Rb gene encodes a type of protein called a tumor suppressor. Children only get eye tumors when both Rb alleles make a nonfunctional protein. Knowing this, do you think the mode of inheritance is different than what you previously thought? How so?
30. What does it mean when two genes are “linked”?
31. As a human, you have 23 pairs of chromosome. For each pair, one chromosome was maternally derived and the other was paternally derived. During meiosis, chromosome pairs are segregated randomly into haploid cells so that the maternal and paternal chromosome pairs are split up.
a. What is the probability that a human gamete has 20 of 23 maternally derived chromosomes?
b. Which Mendelian principle is responsible for the number of maternally-derived and paternally-derived chromosomes that end up in gametes?
c. What is the probability of having at least one maternally derived chromosome in a gamete?
Pyruvate (pyruvic acid), the final product of glycolysis, has to enter the mitochondria to participate in the Kreb’s cycle.
Which of the following statements about its entry is true and which is false? If false, correct it so that it is true.
1. Pyruvate moves by facilitated diffusion that goes against the concentration gradient.
2. Pyruvate is a lipid soluble molecule moving down its concentration gradient.
3. There must be transport molecules in the mitochondrial membrane.
4. The concentration of pyruvate is likely to be higher inside the mitochondrion than outside.
5. During aerobic respiration, electrons travel downhill from food à NADH à electron transport chain à oxygen.
6. Prokaryotes don’t do glycolysis because they lack mitochondrial membranes.
7. Photosynthesis is to cellular respiration as _________.
a. exergonic is to endergonic.
b. amino acids are to carbohydrates.
c. increasing entropy is to decreasing entropy.
d. anabolic is to catabolic.
e. none of the above.
8. Rank the following compounds according to their oxidation state from LEAST oxidized to MOST oxidized:
a. carbon dioxide, pyruvate, glucose
b. glucose, carbon dioxide, pyruvate
c. pyruvate, carbon dioxide, glucose,
d. pyruvate, glucose, carbon dioxide
e. glucose, pyruvate, carbon dioxide
T / F 9. The Krebs cycle yields NADH and FADH2 but not ATP or GTP.
T / F 10. Every reaction in cellular respiration is spontaneous.
T / F 11. One of the reasons that glycolysis is believed to be one of the most ancient of metabolic processes is that glycolysis neither uses nor needs O2.
T / F 12. Glycolysis occurs in the mitochondria of eukaryotic cells and in the cytoplasm of prokaryotic cells.
T / F 13. During aerobic respiration, energy is gently transferred from food molecules to ATP molecules; during photosynthesis, light energy is used to generate ATP molecules which are used to create food molecules.
For #14-18: An organism is discovered that consumes a considerable amount of sugar, yet does not gain much weight when denied air. Curiously, the organism seems to survive even in the absence of air, and the consumption of sugar increases as air is removed from the organism’s environment. When returned to normal air, the organism does fine. Which of the following could describe the organism?
T / F 14. It is a human cell.
T / F 15. It may be used to produce ethanol.
T / F 16. It is a facultative anaerobe.
T / F 17. The organism obviously lacks the Krebs cycle and electron transport chain.
T / F 18. It must use a molecule other than oxygen to accept electrons from the electron transport chain.
19. Draw a generic eukaryotic cell and a generic prokaryotic cell. Label where the following take place:
glycolysis, fermentation, pyruvate processing, Kreb’s cycle, electron transport chain, oxidative phosphorylation
20. Here is an abstract from an article by Rui-Hua, et al. Inhibition of glycolysis in cancer cells: A novel strategy to overcome drug resistance associated with mitochondrial respiratory defect and hypoxia. 2005 Cancer Research vol. 65, pp. 613-621.
Cancer cells generally exhibit increased glycolysis for ATP generation (the Warburg effect) due in part to mitochondrial respiration injury and hypoxia, which are frequently associated with resistance to therapeutic agents. Here, we report that inhibition of glycolysis severely depletes ATP in cancer cells, especially in clones of cancer cells with mitochondrial respiration defects, and leads to rapid dephosphorylation of the glycolysis-apoptosis integrating molecule BAD at Ser112, relocalization of BAX to mitochondria, and massive cell death. Importantly, inhibition of glycolysis effectively kills colon cancer cells and lymphoma cells in a hypoxic environment in which the cancer cells exhibit high glycolytic activity and decreased sensitivity to common anticancer agents. Depletion of ATP by glycolytic inhibition also potently induced apoptosis in multidrug-resistant cells, suggesting that deprivation of cellular energy supply may be an effective way to overcome multidrug resistance. Our study shows a promising therapeutic strategy to effectively kill cancer cells and overcome drug resistance. Because the Warburg effect and hypoxia are frequently seen in human cancers, these findings may have broad clinical implications.
A. How can cells generate ATP in the absence of functioning mitochondria?
B. How much ATP can be generated in the absence of mitochondria?
C. What would happen to the pH in cancer cells due to this metabolism?