In the tiny model plant Arabidopsis, the recessive allele hyg confers seed resis
ID: 62345 • Letter: I
Question
In the tiny model plant Arabidopsis, the recessive allele hyg confers seed resistance to the drug hygromycin, and her, a recessive allele of a different gene, confers seed resistance to herbicide. A plant that was homozygous hyg/hyg her/her was crossed with wild type, and the F1 was selfed. Seeds resulting from the F1 self were placed on petri dishes containing hygromycin and herbicide. As it turns out the F2 progeney showed that 18 percent grew when plated. Calculate the genetic distance between hyg and her.
Explanation / Answer
If the genes are actually not linked, then you can expect 1/16 or 6.25% of the seeds to germinate in the presence of both hygromycin and herbicide.
But as you said, 18% seeds germinated in the presence of hygromycin and herbicide, so the genes are linked,
In this scenario, the crosses will be
P hyg her/hyg her X hyg+ her+/ hyg+her+
F1 hyg+ her+/hyg her X hyg+ her+/ hyg her
F2 18% hyg her/ hyg her
Now this class is a representation of combination of two parental chromosomes, so
P(hyg her) x p (hyg her) = (1/2 parentals)2= 0.18
Parental will be 0.85
Recombinants will be 1-0.85=0.15
Map distance= Number of recombinant offspring/Total number of offspringx100= 15/100x100=15 map units
So, we can say the distance between the genes 0.15 cM