3. In green turtles, an odd number of plates on there shell is dominant over an
ID: 30544 • Letter: 3
Question
3. In green turtles, an odd number of plates on there shell is dominant over an even number of plates. On the same chromosome is a gene for ear spot color with red being dominant over orange. On this same chromosome is the gene for strip color on the body with yellow being incompletely dominant with blue strips. These turtles were crossed in a breeding experiments and the following data was determined. Cross One: ODD, RED (heterozygote) with a EVEN, ORANGE 487 odd, red 438 even, orange 125 odd, orange 138 even, red Cross Two: ODD, Green (heterozygote) with a EVEN, YELLOW 328 odd, green 316 even yellow 31 even, green 29 odd, yellow Cross Three: RED, Green (heterozygote) with a ORANGE, YELLOW 421 red, green 387 orange, yellow 67 red, yellow 68 orange, green Determine the recombination rate for each trait and make a map of the chromosome showing the spatial relationships between the genes.Explanation / Answer
a) Cross 1:
For the trait odd red the recombination rate can be calculated by calculating the progeny that shows their separation i.e.
Odd red recombination rate= 25+38/ 2003* 100
=63/2003*100 = 3.145%
Cross 2:
For the trait odd green the recombination rate can be calculated by calculating the progeny that shows their separation i.e.
Odd green recombination rate= 68+79/ 791* 100
= 147/791*100
= 18.58%
Cross 3:
For the trait red green the recombination rate can be calculated by calculating the progeny that shows their separation i.e.
Red green recombination rate= 71+68/ 947* 100
= 139/947*100
= 14.67%
b) A map of the chromosome showing spatial relationship between the genes can be drawn by estimating the recombination values. In this case the recombination value for odd green (18.58%) is closer to the odd red+ red green= 3.14+14.67 = 17.81%. Therefore, red should be located between odd and green. This means that the map can be made as
odd--------red--------------green
3.14 14.67
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