Which of the following statements about pronuclear injection is accurate?
a. DNA is inserted into any specific cell type whose fate has already been determined, such as skin cells.
b. DNA is inserted into a single celled mouse zygote so that the insertion can be passed to most/all cells of the resulting mouse embryo.
c. DNA that is inserted can integrate randomly anywhere in the genome of the mouse.
d. DNA that is inserted integrates at a specific site in the genome via homologous recombination.
e. DNA that is inserted includes an antibiotic resistance marker to be able to select for the embryonic stem cells (growing in dishes) that have incorporated the new DNA.
f. both A and C
g. both B and C
To generate a gene knockout in mice, which of the following is required?
a. a method for screening to verify insertion into the target gene in the mouse chromosome.
b. regions of homology between the researcher-engineered gene and the target gene in the mouse chromosome.
c. mouse Embryonic stem (ES) cells, to increase the chance that many cells in the host mouse including germline cells (which will form sperm and eggs) will carry the change.
d. all of the above
You follow the scheme outlined in to generate a knockout of the mouse gene Myo6, which is involved in motor coordination and movement. You derive ES cells from WT (Agouti-coated) mice, and disrupt one copy of the Myo6 gene in these ES cells. You then you transplant the ES cells into a blastocyst from a black mouse to generate a chimera. As shown in the last step in the figure, you then cross the chimera to a homozygous black mouse.
Some chimeric animals do not produce offspring carrying the gene replacement, while other chimeric animals with the same gene replacement can easily produce offspring carrying the gene replacement. Why?
a. chimeric animals are unable to produce offspring.
b. the gene replacement prevents correct gamete formation.
c. some chimeras have a germline entirely composed of cells from the blastocyst rather than the modified cells whereas others have a germline entirely composed of modified cells rather than cells from the blastocyst.
When you cross the chimera with the black mouse, amongst 20 F1 progeny obtained, you see some Agouti mice and some Black mice. Which of the following statements about the F1 progeny is true?
a. all the F1 that are Agouti will be homozygous for the myo6 knockout allele.
b. all the F1 that are Agouti will be heterozygous for the myo6 knockout allele.
c. 1/2 of the F1 that are Agouti will be heterozygous for myo6 knockout allele.
d. all the F1 that are Black will be homozygous for the myo6 knockout allele.
