Knockout Mice - Chapter 20 - Unit 4

Question 1

how are knockout mice produced

Answer 1

they are produced by homologous recombination

Question 2

mouse embryo genesis steps/stages

Answer 2

1. fertilization
2. get formation of zygote
3. undergoes multiple cleavages (multiple cell divisions)
4. 16-cell stage: morula; has gone through four cleavages (2^4)
5. 64 cell stage: blastocyst; has gone through six cleavages (2^6)

Question 3

what happens to 13 out of the 64 cells

Answer 3

• they are green

- form the inner cell mass (ICM)

Question 4

what is the inner cell mass

Answer 4

its the source of embryonic stem cells (ESCs) which can differentiate to many cells in the body (they are pluispotent)

Question 5

what happens to 51 out of the 64 cells

Answer 5

• purple cells

- they are trophoblast that form the placenta

Question 6

what is endogenous retrovirus (ERV)

Answer 6

elements a that are in our genomes; inactive most of the time

Question 7

what are envelope of the virus

Answer 7

are the envelope genes known as syncytins

Question 8

what are syncytins

Answer 8

genes that help facilitate cellular fusion that then forms syncytotrophoblast because the ENV genes expressed by the mother contain trophoblasts and they also form the placenta

Question 9

what is it called when a mammal gets infected with an infectious retrovirus and another neighboring mammal get it from them

Answer 9

horizontal transmission (intra- and inter- species)

Question 10

what is it called when a mammal gets infected with an infectious retrovirus and its germ-line gets infected and they have offspring

Answer 10

vertical transmission (transmission to offspring)

Question 11

what are the three outcomes that could possibly happen when a vector is inserted into the embryonic stem cells of a brown mouse (AA)

Answer 11

1. target insertion–> ESCs: neoR & tk-
2. random insertion–> ESCs: neoR & tk+
3. no insertion–> ESCs: neoS & tk-

Question 12

what are the steps of knockout mice

Answer 12

1. make vector
2. insert vector in ESCs of brown mouse (AA)
3. subject ESCs to selection
4. inject ESCs that have survived (neoR, tk-) into blastocyst of a black mouse (aa)
5. implant the blastocysts into the uterus of the surrogate mother (the black mouse)
6. observe coat color of the pups (baby mice)
7. continue to breed until you get all brown pups- indicated that all of the ESCs are knocked out for that gene

Question 13

what does G418 do

Answer 13

it kills embryonic stem cells making it neoS (its a neo analog)

Question 14

what does ganciclouir do

Answer 14

it kills embryonic stem cells making it tk+ (its a tk analog)

Question 15

what is meant by a successful engraftment and how do you don’t get a successful one

Answer 15

it means that the implant that was put into the mother worked and the pups were a mixture or black and brown (the embryonic stem cells have made it into the inner mass cells)

if it doesn’t work it because of chance.