2) (10 point question) Many people lovecolorful and tasty tomatoes and an ambitious student inhorticulture wants to breed such a tomato variety. He searched allthe available tomato genetic resources, and found the two inbredlines he needed. One line produces the tomatoes with a colorfulred-green-yellow mosaic pattern (rrTT), and the other strain is'very tasty' (RRtt).
When the student crossed the two strains together, he made thefollowing observations:
In the F1 generation, all the ripe tomatoes have a regular redcolor and a regular flavor. The student tasted tomatoes from over40 individual plants, and was sick with regular tastingtomatoes.
In the F2 progeny, the student sampled 1000 tomato plants: 498had red-color tomatoes with normal taste, 248 colorful tomatoeswith normal taste, and 254 red-color tomatoes with great taste. Hewas disappointed not to find any colorful tomatoes with greattaste. He then sampled another 2000 F2 plants: 998 had red-colortomatoes with normal taste, 511 colorful tomatoes with normaltaste, 488 red-color tomatoes with great taste, and 3 colorfultomatoes with great taste; he was so happy to find what hewanted!!!
Based on these experimental results, he realized that thealleles he needs are recessive and the two genes are linked.
A) (4 points) How closely linked are ther and t genes? Please explain your strategy tocalculate the distance.
B) (2 points) A testcross with the F1 can beused to further define the genetic distance between the two genes.Indicate the ratio of progeny phenotypes that you'd expect(describe phenotypes) from this cross based on the map distance youpropose for part a).
C) (2 points) The tomato genome has now beensequenced and genes on the chromosome are in the following orderOPQRSTU. The respective physical distances on the chromosomebetween these seven genes are very similar. But we now know thatthere is a 'cold spot' between genes RT and 'hot spots' between PQand TU. Draw a representation of the genetic map relative to thephysical map (both maps are needed here) for this part of thetomato genome. Show the relative (approximate) locations of thegenes on the two maps.
D) (2 points) What can you predict about thechromosome chromatin structure between the R and T genes?
