Frequently Asked Questions

Can you help me create a congenic line of mice?

We have put together a packet of information providing researchers with a volume of information of how to start, and maintain, their congenic lines.  This can be downloaded in PDF format from THIS LINK.  We recommend that all researchers read through this file prior to starting a new congeninc line.

Do I send my mice to DartMouse?

No.  You send tail clippings (~1 cm), or other tissue sample, to our lab, from which we extract DNA before beginning our analysis.

Will I be charged a fee for DNA extraction if I am submitting tissue samples for Genetic Background Check or Speed Congenic services?

No.  The cost of DNA extraction is included in the pricing for these services (as well as our Three-Strain Analysis service). We do not reduce the price if the samples submitted for your project contain pre-extracted DNA.

Does DartMouse carry out the breeding of my mice?

No.  All of your mice stay in-house with you at your institution. You do the breeding.  Our lab offers breeding strategies and recommendations at each generation to ensure that you are breeding using the best carrier of your gene of interest.

Does DartMouse make transgenic/knockout mice?

No.  We do not perform these functions.  We perform genetic analyses of SNPs, and provide important analysis and advice. For making a transgenic or knockout mouse, we recommend using our sister core facility at Dartmouth.

I have DNA, not tail clips. May I send these to you?

We will accept either tail clippings or DNA, but we prefer a tail snip over pre-extracted DNA whenever possible.  This ensures that our rigorous quality control (QC) measures are sustained throughout the entire process.  If you can only send us DNA, we will measure the purity and concentration when the samples arrive within our facility.  If the samples do not meet our internal QC threshold for purity or concentration of the DNA, we may request that you submit additional DNA or tissue from your mice.

How many samples from a given mouse line should I send for an accurate background check?

To get a comprehensive genetic background check of your colony populations, you should send samples from every breeder in the line.  Each breeder has an equal chance to contain contamination in the genome, so every breeder in the colony should be scanned to give an accurate picture of the population.  However, DartMouse is equipped to work on any sized project, so if this "comprehensive survey" does not fit your lab's financial plans, we are happy to work on a project size that does fit with your lab.

What is the benefit to screening at every generation in a congenic project?

The speed congenic (or "marker assisted") strategy works by taking advantage of the random crossing-over and sorting events during meiosis.  By screening all of the male carriers of your gene of interest at each generation, we can ensure that you are using the mouse that is “most back-crossed” at each generation due to these random meiosis events. Without screening your mice, you have as equal a chance to choose the “least back-crossed” mouse as you have to choose the most.  Using the best mouse at each generation is what allows the speed congenic breeding strategy to achieve >99% genetic purity through back-crossing in only ~1.5 years.  Also important to this approach is an appropriately large panel of carriers:  without a sufficiently large group of carriers to screen here, the chances of identifying a pup with a "fortuitous" meiotic event are significantly reduced and the power of the speed congenic approach is lessened.

Why do you prefer male mice?

Our breeding strategy recommends that you place your best male carrier into a cage with two or three females of your destination strain, and (typically) the second-best male in a separate cage with two or three additional females. This allows researchers to generate many more pups at each generation by creating litters more rapidly.  If you are using a female carrier, you will only be able to create one litter of pups in the same time frame as you would generate two or three litters with a male carrier.

NOTE: The exception to this is when studying sex- (X-chromosome) linked traits; in this case, you will want to breed the “best” female.


For a speed congenic project, how many mouse tails should I send at each generation?

For a speed congenic project, we recommend that, at each generation, you send samples from ten male carriers of your gene of interest, although the speed congenic approach works whether you send fewer or more than ten.  We have found ten to be at the “sweet spot” between (on the one hand) efficacy of the speed congenic approach, and (on the other hand) burdensome cost and effort to the investigator.  Many fewer than ten significantly reduces the effectiveness of the speed congenic strategy (decreasing further with each fewer sample); conversely, more than ten increases effectiveness, but at the cost of diminishing returns on the investment, in terms of per-diems and additional screenings.

Why do you recommend your particular breeding strategies?

The "ideal" generation size for a speed congenic project is 10 male mice.  An average litter size is 7-10 pups (this can be larger or smaller on average depending on the inbred strains used for your particular back-cross project).  Approximately half of those pups will carry your gene of interest.  Approximately half of the carriers will be male.  To consistently have the recommended ten male carriers at each generation, you should plan to generate around 40 pups.

I’ve been breeding using brother/sister pairs for years. How could I still have contamination?

If the original founder mice had not been background-checked at the beginning of the sibling breeding program they could have had contamination from the outset. These genetic differences will have been maintained in the population, through Hardy-Weinberg equilibrium. Brother-sister matings will not typically reduce the overall percentage of unwanted (contaminating) genetic material, but rather will "fix" it into place within the genome. However, DartMouse can identify contaminating regions of the genome, and provide you the support you need to help you “speed” back-cross your mice onto any pure inbred strain you wish.

Do you work with researchers outside of Dartmouth College?

Yes.  We have worked with researchers at institutions across the country and around the world.  We have also worked with academics, as well as clients from industry.  You can see a list of institutions with a DartMouse client and see that placement on a map on our Clients page.

Are prices different if I am (or am not) funded by the NIH?  What about non-profit status?

No.  All investigators are charged the same price for our analysis service, regardless of geographic location or institution affiliation.

What Credit Cards do you accept for payment?

We accept Visa, MasterCard, and Discover.

The project accession form is giving me problems.  What should I do?

We have found that many of the problems with the accession form are resolved by first downloading (saving) a copy of the form to your computer, rather than attempting to edit the form directly in your browser.  Once you have downloaded a copy to your computer, you can make (and save) edits to the form, then email a copy of this edited form.  If this is still not working properly, you can simply print out a copy of your completed form, then scan and email the form back to us, or fax the form to our facility (please contact us for our fax number in this case).

What kind of quality control do you implement in your services?

Our full  regiment of Quality Assurance measures are detailed on the "Services" page.