i need to develop a double mutant arabidopsis plant for that i have both the gene mutant plant separately now i want to cross both plant. those genes are presented in same chromosome. so i want know what is the frequency to get the double mutant?
It depends on several factors, in particular how distant they are from each other.
If you have a genetic map already available, a map unit corresponds to 1% of recombination and the maximum is 50%.
Otherwise you have to estimate it yourself, but the way depends on the genes.
If these genes code for known enzymes you might be able to design an assay.
If you know their sequence and can design allele-specific primers for amplifying them or use allele-specific restriction enzymes, you can amplify them through a PCR and run them in agarose gel electrophoresis or cleavage them and then run them or both.
If you don't know enough, you can cross two homozygous ones in order to obtain one that is heterozygous for both genes and then cross it with a homozygous recessive for both.
Doing this you could directly observe the genotype of each gamete from the phenotype of the offspring.
Generally the mutations are recessive so that in your F1 population of the cross between two mutant plants, frequency of getting both mutants are '0' . However, in your F2 population derived through selfing of F1, frequency of getting plants with both mutants should be 25%.
Frequency in F1 and F2 generations may vary from the above, depending on your parent's genotypes and dominance/recessiveness of your mutant genes. If both mutant genes are homocygous dominant, you will get 100% of the plants showing both mutant genes in your F1 generation and 75% (25% homocygous and 50% heterogous) of the plants having both mutant genes in your F2 population . If one mutant is homocygous dominant and other is homocygous recessive, you may get about 16% of your F2 population having both mutant genes.
It depends on the existance of heterozygous rearrangenements on the chromosomes (inversion)
Ariadni Mavrou Nicolò M. Villa Demuni Sumith De Zoysa Abeysiriwardena Beatriz Goñi thanks to all answering this question. the distance between those genes was 3375bp whether this distance was enough or what is the minimum distance required for recombination? what is the recombination frequency to get double mutant?
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