01:119:115 Final: Outcomes 22
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Homozygous recessive loss of function mutations in any one of 4 different genes in C. elegans worms (genes A, B, C, or D) results in female worms that don't form proper egg-laying structures, called vulvas, as shown in Lines 2-5 of the data table below. In vulvaless females, the fertilized eggs hatch and baby worms develop inside the mother, killing her in the process.
genotype | phenotype | |
1 | AA BB CC DD (wild type) | normal vulva |
2 | aa BB CC DD | No vulva |
3 | AA bb CC DD | no vulva |
4 | AA BB cc DD | no vulva |
5 | AA BB CC dd | no vulva |
You would like to figure out the order in which these genes act during the creation of the vulva (you cannot assume it will be A--->B--->C--->D as the gene names are arbitrary). Your friend tells you to perform epistasis analysis by making double mutants between the different homozygous recessive mutants and analyzing the phenotype of the double mutant. For example, she asks you to examine the phenotype of aabbCCDD (double mutant of genes A and B) and compare this to the single mutants to figure out whether gene A acts earlier than gene B, or vice versa. You know this won't work. Why not? Pick the ONE BEST choice:
a. The phenotype of the single mutant is already pretty severe. The double mutant will most likely be dead, therefore epistasis analysis won't be possible.
b. Each of the single mutants (aaBBCCDD) and (AAbbCCDD) has the same mutant phenotype i.e., no vulva. Epistasis analysis between any 2 genes is only possible when the mutant phenotypes for each gene is different.
c. Epistasis analysis involves making triple mutants (such as aabbccDD) in order to learn something about how the genes are ordered.
d. Epistasis analysis can never be carried out with null loss of function mutations. The mutations being analyzed all have to be dominant gain of function alleles.
To address your concern, you first generate overactive alleles of either gene A (denoted as A*) or gene B (denoted as B*). As shown in lines 6-7 of the table below, C. elegans that have one of these overactive alleles produce multiple vulvas.
Genotype | Phenotype | |
6 | A*A BB CC DD | multiple vulvas |
7 | AA B*B CC DD | multiple vulvas |
To find out the order in which these genes act, you combine the overactive alleles with different loss of function alleles and observe the phenotype in double mutants (see Lines 8-11).
Genotype | Phenotype | |
8 | A*A bb CC DD | multiple vulvas |
9 | A*A BB cc DD | multiple vulvas |
10 | A*A BB CC dd | no vulva |
11 | AA B*B cc DD | multiple vulvas |
Based on the data in the table, what is the order in which these 4 genes normally act in wild-type C. elegans in order to produce a wild-type/normal vulva?
a. A----> B----->C----->D ---> Vulva
b. D----> B----->C----->A----> Vulva
c. B----> C----->A----->D----> Vulva
d. C----> B----->A----->D----> Vulva
e. C----> B----->D----->A----> Vulva
f. don't have enough data to make any conclusions
Based on the vulva formation phenotype of the double mutants, which of the following statement(s) accurately describes the genetic interactions between the A* allele and alleles of other genes affecting vulva formation? Pick ALL that apply:
a. The A* allele is epistatic to homozygous recessive loss of function mutations in gene B
b. A homozygous recessive loss of function mutation in gene B is epistatic to the A* allele
c. Homozygous recessive loss of function mutation in gene D is epistatic to the A* allele
d. The A* allele is epistatic to homozygous recessive loss of function mutation in gene D
e. The A* allele enhances the homozygous recessive loss of function mutation in gene D
1. Match the word 1-39 above, with the descriptions labled a-t. Word 1-39 can be uses only one please!!
1. alveolar macrophages 2. alveoli 3. Bohr effect 4. bronchi 5. bronchiole 6. cerebral cortex 7. chloride shift 8. compliance 9. costal breathing 10. DaltonĆ¢ĀĀs law 11. diaphragmatic breathing 12. epiglottis 13. eupnea 14. expiratory reserve volume 15. fauces 16. functional residual capacity 17. Haldane effect 18. HenryĆ¢ĀĀs law 19. hilum 20. hypothalamus 21. inferior, middle, and superior nasal meatuses 22. inspiratory capacity 23. larynx 24. limbic system 25. medulla oblongata 26. nose 27. paranasal sinuses 28. pharynx 29. pleural membranes 30. pons 31. primary bronchus 32. secondary bronchus 33. surface tension 34. surfactant 35. terminal bronchiole 36. tertiary bronchus 37. total lung capacity 38. trachea 39. vital capacity
a) -------------------- serves as a sound resonating chamber; contains tonsils; directs air inferiorly b) ------------------- passes air from pharynx into windpipe; site of sound production c) ------------------ resonate(s) sound; not part of pharynx D) ------------------ opening from oral cavity into pharynx E) ----------------- carries air to a segment of a lung F) -------------------- carries air directly into a respiratory bronchiole G) ----------------- surround the lungs H) ------------------ reduces surface tension at sites of gas exchange i) -------------------- actual sites of gas exchange j) --------------------- normal, quiet breathing k) ----------------------- shallow breathing using just the external intercostal muscles l) ------------------ amount of effort required to expand the lungs and chest wall m) ------------------- tidal volume + inspiratory reserve volume, usually about 3600 mL in males n) ----------------- tidal volume + inspiratory reserve volume + expiratory reserve volume; usually about 4800 mL in males o) ------------------- residual volume + expiratory reserve volume; usually about 2400 mL in males p) -------------------- states that the amount of gas that will dissolve in a liquid is proportional to the partial pressure of that gas and its solubility q) ---------------- when pH decreases, O2 saturation of hemoglobin decreases r) ------------------ each gas in a mixture of gases exerts its own partial pressure s) ------------------- sets basic rhythm of breathing t) ------------------------ includes the pontine respiratory group |