BIOC14H3 Lecture : BIOC14 : Lec 10 : Article 2 - Genetic Dissection of Neural Circuits

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amethystsardine553

30 Dec 2011

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Bioc14 : lec 10 : article 2 discussion (only sections 1 &2) We are looking at the relationship btn genes and behaviors in terms of intervening things (ex: neuron itself as the unit of activity in the brain) Transgenic and knock-out mice for generating mice which lack certain genes or certain genes added: Based on these models we can assess the effect of gene. Therefore, you want some control over when this gene is knocked out/expressed. This kind of technology used in other model organism like drosophila (fruit flies), but mouse = classic model. Dna microinjection into single-cell embryos as a way to produce transgenic mice with multiple copies of randomly inserted dna vs. Specifically targeting certain regions of the genome via homologous recombination to generate replacements at very specific loci. Studying individual genes isn t sufficient for studying how the brain works and studying individual cells is also not sufficient b/c cells work in groups/circuits.

Related Questions

Many papers I have seen describing transgenic rodent models (andpresumably applicable to other model organisms) involve theknock-in, or modification to, a single gene, possibly two genes.With respect to recombineering techniques, what prevents targetingmultiple genes in a single organism? For instance, if I wanted tosimultaneously knock-in some genes and knock-out others within thesame mouse, would I be forced to generate individually modifiedtransgenic lines and then do some "fancy" breeding to generate themultiple-modified mice?

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.

Q.In the non-9:3:3:1 ratio dihybrid cross below, there are 3 classes of phenotypes: white, pink, red which of the following is NOT true?

9 A_B_ white

3 A_bb pink

3 aaB_ red

1 aabb red

a.) phenotype is dependent on the genotype of gene B

b.) This is an example of recessive episasis

c.) aa is epistatic to B_, and bb

d.) phenotype is dependent on the genotype of gene A

Q,When choosing a selectable marker, you...

a.) choose a enhancer for your gene of interest

b.) choose a rescue gene to save your gene of interest

c.) choose a resistant gene that will allow for colony screening

d.) choose a gene that encodes for DNA replication

Q.The following steps detail an experiment resulting in transgenic mice with a knockout gene for fur color. Recall that agouti (brown) mice are A/A;M/M and black fur coats are a/a;M/M . List the steps in their correct chronological order.

1.Inject transformed agouti embryotic cells into an a/a;M/M embryo to produce A/A;M/m and a/a;M/M altered embryo

2.Self-cross hemizygous mice to produce homozygous transgenic mice (A/-;M/m)

3.Create a a targeting vector containing tk+ for ganciclovir sensitivity, neoR for neomycin resistance, and the gene encoding fur color.

4.Observe mice with chimeric phenotype and cross them with black a/a;M/M mice to produce transgenic hemizygous progeny (A/a;M/m)

5.Isolate all transformed embryonic stem cells that show homologous recombination and inject them into a embryonic stem cells of an agouti mouse.

a.) 3,5,4,1,2

b.) 1,5,3,4,2

c.) 3,5,1,4,2

d.) 5,3,2,4,2

If dog 1 has is black with alleles (A_B_) , and dog 2 is brown with (aaB_), and dog 3 is yellow with (_ _bb) alleles, what kind of epistasis is this and what color would dog 4 be if he was (AAbb).

1. Recessive epistasis, Yellow

2. Recessive epistasis, Black

3. Dominant epistasis, Yellow

4. Dominant epistasis, Black

A gene interaction in which pair of recessive genes at one locus prevents expression of dominant allele at another locus called

a. incomplete dominance

b. epistatis

c. complete dominance

d. polygenic inheritance

BIOC14H3 Lecture : BIOC14 : Lec 10 : Article 2 - Genetic Dissection of Neural Circuits

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