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marker assister backcrossing - (May/08/2007 )


could anyone explain briefly to me what marker assisted backcrossing is?

i tried reading up on internet but i get info thats too i cant see how
those pieces fits to together.

hope to get a gud general idea of what it is. thanks


You usually use maker assisted backcrossing after crossing two genome donor parents.

Let's say you cross A x B

In F1 you'll have 50% genome A and 50% genome B right?

But imagine you want your plants to be closer to parent A (because it has better agronomic features or so). Then you'll have to cross them with your A parent (F1 x A) - this is backcrossing, and can be done for as many generations as you want.

The marker assisted bit is about using molecular markers (like micro or minisatelites) to assess the percentage of the donor parent genome. You need markers that behave differently in both parents (A and cool.gif. This can help you decide how many times will you need to backcross your plants.

I don't know if I've been clear. If not just reply and I'll try to answer in some other way. smile.gif


thanks you:) i have also read up a bit more and understood better but i still a few questions.

first, do u mean it depends on what type of markers we use to determine how many generation we need to backcross?

from what i understood it is like tracking down markers. can we have markers for the recurrent parents instead of donor or
even have markers for both parents?

could u also give me an example how this could be applied? and what are the types of markers used.

thank you so much.


Sorry for taking so long to answer, but I haven't had the time to come to the forum lately...

Let me see if I understand your questions.

For the first one, the number of times you decide to backcross depends on how good your markers are (and how many markers you use). If you use different markers you will get different information, so you'll have to decide which ones to use according to your aims... And the more the merrier, because with more markers you can get more information on how much DNA is present from both parents.
I suppose you can use markers for both donor parents yeah, if you have the money tongue.gif

For instance, imagine there are two plants (again A and B ). Plant A is the agronomically important one and B has a gene that you want to insert in A. So you cross them and select the progeny that has the gene of interest. Then you just backcross all those plants with parent A for I don't know how many times until you get plants very similar to A, but with the gene of interest.

If you're very lucky there might be already some molecular markers described for those donor parents. If not you'll have to do some experiments before and determine which markers are suitable for you to distinguish between A and B. The most comon DNA-based markers are micro and minisatelites, AFLPs, RAPDs, SNPs, etc. They have advantages and disadvantages, you just have to choose the ones that are more suitable for your study.