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what are 7 advantages to using a mouse as a model organism?

- easy to breed and house ( but expensive) - easy to control the environment that the mice are in - physiological similarities with humans - well developed physiological techniques for mousegenetically homogenous (inbred) strains available - deposition of the vaginal plug - strains can be used across labs across the world


when do mice reach sexual maturity?

around week 4 post birth


what is the litter size of mice?

up to 10 pups


is the physiology of the mouse strain dependent?



what about the genetics of the mouse makes them suitable for human studies?

all human genes have counterparts in the mouse genome. thus cloning of a human gene leads directly to cloning of a mouse homologue which can be used for genetic, molecular and biochemical studies that can then be extrapolated back to an understanding of the function of the human gene. In only a subset of cases are mammalian genes conserved within a genome of the flies of worms


what is the most commonly used mouse strain?



why is it important to keep buying new mice from your original source when keeping a mouse strain?

it is important to keep repopulating your strain with founders because genetic drift can occur within the populations causing th strain to diverge from the original, meaning that there is less similarity between strains used by other labs and less reliable and comparable phenotypes therefore


why is it important to always get the same strain from the same supplier even though they are the same strain?

because there can always be divergence between two sub strains due to genetic drift


why is homogeneity so important in mouse strains?

normal development and physiology can vary significantly from one strain of mice to the next and in the analysis of, mutants, it is often not possible to distinguish subtle effects due to the mutation itself, from effects dye to other genes within the background of the mutant strain. to make this distinction, it is essential to be able to compare animals with the same genetic background. Phenotypic differences that persist between these a mutant and a wild type from a strain must be a consequence of the mutant allele.


what species of mouse are normally used in mouse experiments?

musculus musculus domesticus


how many generations of inbreeding do you need to ensure the strain is 98.7% isogenic?



how many generations of inbreeding do you need to do to ensure your strain is 99.9999% isogenic?



what is important to remember about different strains (inbred lines) of mice that are used. give 2 examples of this.

they all have different characteristics and are different genetically. For example the C57BL/6 is seizure resistant so epilepsy analysis in this mouse would not be good. The C3H has poor spatial learning so experiments relating to this would not be suitable


what is the C3H inbred line of mouse bad at?

spatial learning


what is the C57BL/6 mouse resistant to?



in an ideal world, how would mutations occur in mouse strains and why?

they would occur spontaneously in strains, the way you would know that the phenotype observed from the mutation would only be due to it, and not from any other genetic background


Due to the fact it is unlikely for interesting mutations to occur spontaneoulsy, how can mutations be induced and what is the protocol for ensuring the mice are coisogenic?

You can induce mutations and then either view them in heterozygous animals if they are dominant, or in homozygous animals if they are recessive. They can then be continuously inbreed to create its own strain that is homozygous at all loci. Or if it cannot be maintained as a homozygous then it can be maintained as a heterozygous by continuous backcrossing into the original strain. In both cases they are coisogenic meaning that they are genetically identical to the sister strain expect at the mutant loci


what is genetic drift?

the constant tendency for genes to evolve. This is the introduction of new alleles into the strain. This can result in one strain being developed into many different strains.


after how many generations of a colony being separated from its parent colony should it be considered a sub colony and what is the mechanism behind this?

20 generations. This is due to genetic drift


how common are spontaneous mutations?

5 X 10^-6 per gene per generations


how many nucleotides are there in the mouse genome?

3 x 10^9 nucleotides


after how many generations is there a 90% chance that two substring differ at one or more locus?



after 16 generations, what is the probability that two substring differa t one or more loci?



how can substring arise from bad strain maintenance? (2)

substring can arise fi there is residual heterzygosity within a strain caused by incomplete inbreeding at the time of separation from progenitor strain. This means that not all loci were homozygous for an allele and so the diffferent allele could replace the normally and cause a sublime. this is why it is important to ensure inbreeding is carried out extensively. 2. substring can also arise from genetic drift if the strain is not constantly replenished by the progenitor strain


how do you maintain in bred lines?

you cross brother and sisters


how can you get rid of spontaneous mutations which could eventually be incorporated into genetic drift and cause the formation of a substrain?

Once you have identified a mouse that has a phenotypic mutation, you then "inheritance test" them. This involves backcrossing the mice and scoring the ratios of the offspring. if the homo mouse is crossed with a het then the ratio will be different than if it was crossed with a homo non mutant (all wild type if recessive). Once identified, you then get rid of the het rogue mice.


what is another word for inheritance testing?

test crossing


although spontaneous mutations can be damaging, how can they also be useful? give 3 examples

They can be useful if they give rise to interesting phenotypes. reduced insulin secretion, impaired memory and retinal degeneration have manifested themselves in spontaneous mutations


how can you reduce genetic drift?

obtain mice from a reputable source, maintain good records to enable mutations to be bred out, cryropreserve a large number of embryos from your colony and return them every 10 generations to replenish, replenish from the original source


what is quantitative genetics?

it is the study of phenotypes that are continuous rather than discrete and the genes associated with them