Animal Breeding and Genetics: Concepts and Applications
True/False Questions in Animal Breeding and Genetics
General Concepts
1. Animal domestication processes are exclusively based on artificial selection (False)
2. All quantitative traits present more than 20 phenotypic classes (False)
3. Highly inbred lines can be used to analyze the environmental contribution to a given trait (True)
4. The breeding value of an animal is always constant, independently of the environment (False)
5. The breeding value of the offspring of an individual can be half of its breeding value (True)
6. A trait with higher narrow sense heritability (h2) will respond better to artificial selection (True)
7. The breeding value of an individual is the difference between the population mean and the mean of the progeny obtained when this individual is crossed with a random animal from the population (False)
8. Narrow sense heritability (h2) equals total genetic variance when there is no environmental variation (False)
9. The selection differential (S) and the response to selection (R) are equal when the narrow sense heritability (h2) is 1 (True)
10. Outcrossing is never beneficial because of mixing genetic contributions (False)
11. In an experiment of artificial selection of the quantitative trait “weight”, the selection differential is equal to 40g. Therefore, the expected genetic gain is 20g when the realized heritability of the trait is 50% (True)
12. A line that has been selected during several generations to increase the value of a quantitative trait always maintains the achieved increment when no more selection is applied (False)
13. In traits that can only be measured in one sex, it is not possible to apply selection in the sex that cannot be measured (False)
14. The breeding value of an animal depends on the narrow sense heritability (h2) of a trait (True)
15. Inbreeding depression is caused by gain of genetic variance and is related to an increase in heterozygosity (False)
16. In pyramidal structure breeding programs, genetic improvement is realized with a small number of animals in which selection is practiced (True)
17. Crossbreeding and selection can be used to increase the level of performance we obtain for a given trait (True)
18. Obtaining highly inbred lines in domestic animals is very difficult because traits related to fitness have strong inbreeding depression (True)
19. Introgression allows the transfer of one breed to another as a result of hybridization between them followed by repeated backcrossing (True)
20. Molecular methods can be used to compare selective animal breeding and transgenesis for a given trait (True)
Molecular Markers and QTL Analysis
21. RFLPs are restriction enzymes that cut DNA at specific sequences (False)
22. Alleles present in a microsatellite locus may differ in their length (True)
23. Microsatellite loci cannot be used in experiments to identify QTLs by linkage (False)
24. SNPs are used as molecular markers in genome-wide association studies (GWAS) (True)
25. DNA microarrays can be used to perform SNP genotyping (True)
26. In order to begin a QTL analysis, you need two or more breeds that differ genetically with regard to the trait of interest (True)
27. Not all loci that control a quantitative trait are usually identified in linkage studies to identify QTLs (True)
28. A QTL is a molecular marker linked to a locus that affects a quantitative trait (False)
29. Marker-assisted selection (MAS) is always more effective than phenotypic selection (False)
30. When performing genomic selection, the only information needed to select individuals is a high number of molecular markers. No additional information is required to infer the breeding value of individuals (False)
Transgenic Animals
31. The generation of transgenic animals implies the introduction of a DNA fragment from a different species (True)
32. The integration of a transgene in the germ line is a requirement to pass it to the next generation (True)
33. “Genetically edited” animals is a concept that refers to those animals that have been genetically modified using last-generation tools based on target-specific endonucleases (True)
Chimeric Transgenic Mouse Experiment
34. You expect that the animals of the F1 progeny will always be either brown or white (False)
35. In the case that you find that some animals in the F1 progeny are transgenic, then you expect to find half of the progeny to be transgenic (True)
36. If some members of the F1 progeny are transgenic, those will be homozygotes for the transgene (False)
37. All brown animals of the F1 progeny will be transgenic (False)
38. If you generate an F2 progeny by mating two transgenic mice from the F1, you generally expect that some transgenic animals in the F2 will be brown and some transgenic animals will be white (True)
39. If you generate an F2 progeny by mating two transgenic mice from the F1, you expect that ¼ of the F2 will be homozygous for the transgene (True)
40. The expression of the transgene of two animals of the F2 in this experiment can be different due to the position effect (True)
41. The efficiency of integration of constructs derived from transposons or retroviruses is higher than the efficiency simply based on DNA repair by NHEJ (True)
42. Constructs derived from transposons or retroviruses are normally integrated in multiple copies in tandem (True)
43. We always expect that the more tandem copies of a transgene have been integrated, the higher the expression of the transgene will be (False)
44. The approach of somatic cell nuclear transfer is useful to generate transgenic animals typical of farms, such as cows, pigs, and goats (True)
45. In a strategy of somatic cell nuclear transfer in which a Ce-Fat1 gene from C. elegans is used to generate a transgenic pig with meat rich in omega-3, the nuclei containing the Ce-Fat1 genes can be obtained from fibroblasts, but not from any other somatic cell type, such as epidermal or bone cells (False)
Zebrafish Transgenic Line
46. [Context missing for question 46] (True)
47. The construct is derived from a retrovirus (False)
48. To increase the efficiency of integration, we should add loxP sites in the construct (False)
49. We expect that the integration of this construct will occur only in the cells of the liver (False)
50. We expect that after crossing the founder with a wild-type, as indicated in the figure, always half of the F1 progeny will carry the CRE gene (True)
51. If we cross two animals of the F1 that show fluorescence in the eye, we expect that 25% of their progeny in the F2 will be homozygotes for the construct (True)
52. We may find differences in the intensity of the GFP expression in lines created from different founders (True)
53. Adding tamoxifen to an animal homozygous for this construct will induce CRE expression in the eye and GFP in the liver (False)
54. Morpholino injection allows one to alter the translation and splicing of target genes and, therefore, to generate a knockdown (True)
55. The integration of morpholino oligonucleotides in the host genome is restricted by the presence of PAM sequences (False)
56. The knockdown effect of dsRNA injected into a zygote is transitory and will decrease as embryo development proceeds (True)
C. elegans Experiment
57. To generate a knockdown of musculin in C. elegans, you can inject this construct into the … part of the female gonad (True)
58. Feeding C. elegans with bacteria that synthesize … will generate a knockdown of this gene (True)
Balancer Chromosome System
59. In this experimental design, you expect that the “m” mutation will affect the development of the tip of the tail (False)
60. After auto-fertilization, all animals in the progeny that do not express GFP in the tail will be homozygous for the “m” mutation (True)
Homologous Recombination
61. The probability that a DNA fragment will integrate randomly is higher than by homologous recombination (True)
62. A positive selection gene, such as neo, is enough to distinguish whether integration has occurred by homologous recombination or random non-homologous recombination (False)
63. A negative selection gene, such as tk, located inside a construct flanked by two arms of homology, allows one to distinguish whether integration has occurred by homologous recombination or random non-homologous recombination (True)
64. Southern blot and PCR techniques can be used to determine if the transgene has been integrated by homologous recombination (True)
65. The generation of a knock-in transgenic animal can be useful to study whether the function of one gene is equivalent to another gene (True)
66. Including loxP sites in a construct to generate a knockout will increase the probability of homologous recombination, and therefore, there will be fewer cases of random integration (False)
67. The presence of two loxP sites in the same orientation will allow the induction of a deletion of the flanked region in the presence of CRE recombinase (True)
68. The presence of positive selector genes, such as neo with ubiquitous promoters (PGK), in constructs to generate transgenic animals can affect the expression of the transgene (True)
69. Embryonic stem cells (ES cells) are pluripotent and can be cultured in vitro without losing this feature (True)
Transgenic Mice (A and B)
70. 100% of the progeny will show red fluorescence expression from the Red Fluorescent Protein (RFP) (True)
71. The animals from the progeny that show GFP expression in the eye will also show tissue-specific expression (True)
72. 50% of the progeny will show no GFP expression anywhere in the body (True)
Transgenic Zebrafish
73. This experimental design allows the generation of temporally and spatially conditional transgenics (True)
74. All progeny will show red fluorescence expression ubiquitously in the absence of tamoxifen (True)
75. The aim of this experiment is likely to study the development of the eyes (False)
76. The progeny that show GFP expression in the eye will also show GFP expression in the heart after treatment with tamoxifen (True)
77. If we cross two animals of the A line and treat the progeny with tamoxifen, all of them will become green ubiquitously (False)
Gene Editing Technologies
78. Gene editing technologies, such as Zinc-finger nucleases (ZFNs), TALENs, and CRISPR, allow gene targeting and the generation of knockdowns without the need for antibiotic selection genes (True)
79. The CRISPR technology recognizes a specific target gene thanks to a small RNA molecule that guides the Cas9 endonuclease (True)
80. The knockout capability of the CRISPR technology can be biallelic (True)
81. The injection of a gene-specific guide RNA and mRNA that codes for Cas9 allows the generation of a zebrafish knockout (True)
82. The main limitation of the CRISPR technology is its high cost (False)
83. In an experiment with CRISPR technology, two guide RNAs cannot be co-injected together (False)
84. The generation of deactivated Cas9 fused to a transcriptional activator can potentially allow the induction of the transcription of any target gene (True)
Transgenic Cows with Reduced BLG
85. The aim of this experimental design is to generate a transgenic cow knockdown for the BLG gene (True)
86. In this experimental design, the only possibility to know if a cow is transgenic is with a molecular test, such as PCR (False)
87. It might happen that when the transgenic cows are analyzed, some of them might show GFP expression in some other parts outside the skin (True)
88. You expect that the BLG content of the milk of different transgenic lines of cows may be different (True)
89. You expect that the highest level of shRNA against the BLG gene will correlate with the lowest levels of BLG protein in the milk (True)
90. In a case in which the integration has occurred once, you can predict what ratio of the progeny of the cows will be transgenic when they are crossed with a wild-type animal (False)
91. shRNA technology allows one to generate knockdowns, but these can never be conditional (False)
92. In the USA, transgenic salmon for human consumption can already be bought in supermarkets (True)
93. The transgenic salmon made by AquaBounty consists of a knock-in of the growth hormone gene of the Chinook salmon from the Pacific, replacing the growth hormone gene of the Atlantic salmon (False)
94. Dolly the sheep is famous because it was the first transgenic cloned mammal originated from a somatic nucleus (False)
95. The use of CRISPR has been shown to be useful to inactivate genome-wide porcine endogenous retroviruses (PERVs), which is a promising step to decrease the risk of xenozoonosis in xenotransplants (True)
96. Pharming is the concept of using farm transgenic animals to generate therapeutic compounds (True)
97. Approaches by selective breeding and CRISPR could be used to generate hornless transgenic cows (True)
98. The use of transgenic mosquitoes is efficient to reduce the reproduction of mosquitoes in natural conditions to fight diseases such as dengue (True)
99. It is not possible to generate human embryonic stem cells using somatic cell nuclear transfer technology yet (False)
100. In the CRISPR system, including target sites of a guide RNA in a donor vector will increase the probability of inserting the donor vector in the target place of the genome (True)