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PLNT3140 INTRODUCTORY CYTOGENETICS    

Assignment 3

November 8, 2018

This assignment is worth 5% of the course grade. Due Tue. Nov. 20


1. (3 points) In a cross between two Arabidopsis lines, A and B, a map of one chromosome was constructed using a set of co-dominant markers. An excerpt of the mapping data for this cross is shown in panel I. At each locus, the marker is scored as being homozygous for the allele from parent A, homozygous for the allele from parent B, or heterozygous. The order of loci shown in the table corresponds to the order of those loci on the chromosome.
a) At any given locus, what is the predicted ratio for seeing A, H or B?
b) In cross II, parent A was crossed with another Arabidopsis line, C. Thus, the expected phenotypes would be either A, H or C. In this cross, the mapping data look similar to that found in cross I. However, all loci distal to g3883 exhibit only the A phenotype, in all progeny. What is a simple explanation for this result?
c) Based on your answer to b, describe a genetic cross that would test your hypothesis?


I. A x B

II. A x C


      segregating progeny -------------------->
marker/
map posn.
g6844     HHAAAAABHHBAAAHBHHHHABHHHABBAHHBHAHHBAAHHA
g3843     HHAAAAABHHBAAAHBHHHHABHHHAHBAHHBHAHHBAABAA
g2616     HHAAHHHBHHBAAAHBHHH­ABHHHHHHHBBHBHHAHHHHHHH
m210      HHAHHBHHHHHAAAHHBHHHAHHAHAHHHAABHHAHBHABAA
g6837 ­­­­­­­­­­­­­­­­­­­­­­­­­­    HH­AABHHAHBHHBAAHBHHHAHHAHAHHHAABHHAHBHABAA
g10086 ­­­­­­­­­­­­­­­­­­­­­­­­­   AHHHAAHHHAHBHHBAHHHHAHHAHAHHHAAHHHAHBHHBAB
g4564­a    HAAHHBHHHHHAAAHHBHHHAHHAHAHHHAAHHHAHBHHBAA
g3845     HAHHHBHHHAHAAAAHBHH­AHBAHAHHHAAHHHAHBHHHAHH
g4539 ­­­­­­­­­­­­­­­­­­­­­­­­­    AHHHAAHHHAHBHHHAHHHAAHBAHAHHHHAHHBAHBHHHAH
m557      HAHHHBHHHAHAAAAHBHHAAHBAHAHHHHAHHBAHBHHHAH
g3883     HAHHHBHHHAHAAAAHBHHHAHBAHAHHHHAHHBAHBHHHAH
g19833    HAHAHBHH­AHAAAAHBHH­AHBAH­HH­HAHHHA­BAHHAHHBBAH
g19838 ­­­­­­­­­­­­­­­­­­­­­­­­­­­­­   HAHH­AHB­HHAHAAHBHA­HHBAA­HBHHAHHBAAHHHHABHHAH
m272      HAHAHBHHHAH­­AAHBHA­HHBAA­HBHHAHHBAAHHHHABHHAB
g4513     HAHAHBHHHAHAAAAHBHAHHHBAAAHBHHAHBBAAHHHHAB


            segregating progeny -------------------->
marker/
map posn.
g6844     HHAAAAACHHCAAAHCHHHHACHHHACCAHHCHAHHCAAHHA
g3843     HHAAAAACHHCAAAHCHHHHACHHHAHCAHHCHAHHCAACAA
g2616     HHAAHHHCHHCAAAHCHHH­ACHHHHHHHCCHCHHAHHHHHHH
m210      HHAHHCHHHHHAAAHHCHHHAHHAHAHHHAACHHAHCHACAA
g6837 ­­­­­­­­­­­­­­­­­­­­­­­­­­    HH­AACHHAHCHHCAAHCHHHAHHAHAHHHAACHHAHCHACAA
g10086    ­­­­­­­­­­­­­­­­­­­­­­­­­AHHHAAHHHAHCHHCAHHHHAHHAHAHHHAAHHHAHCHHCAC
g4564­a    HAAHHCHHHHHAAAHHCHHHAHHAHAHHHAAHHHAHCHHCAA
g3845     HAHHHCHHHAHAAAAHCHH­AHCAHAHHHAAHHHAHCHHHAHH
g4539 ­­­­­­­­­­­­­­­­­­­­­­­­­    AHHHAAHHHAHCHHHAHHHAAHCAHAHHHHAHHCAHCHHHAH
m557      HAHHHCHHHAHAAAAHCHHAAHCAHAHHHHAHHCAHCHHHAH
g3883     HAHHHCHHHAHAAAAHCHHHAHCAHAHHHHAHHCAHCHHHAH
g19833    AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
g19838 ­­­­­­­­­­­­­­­­­­­­­­­­­­­­­   AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
m272      AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
g4513     AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA


2. (2 points) The pairwise 2-point distances in cM between five loci are shown in Table 1.

Table 1


T175

C35

T93

C66

C35

4.2




T93

18.7

15.6



C66

26.1

25.5

12.1


T50B

30.4

30.5

21.1

12.2


a) Draw a map, showing the order of markers and the distances between adjacent markers.

b) The distances between markers do not appear to be additive. That is, if the map order was BCA, the BA distance is not equal to BC + CA. What is the most likely reason for this observation? Can you suggest a potential solution to this problem?




Notes: If you have questions, it may help to send me a messge at frist@cc.umanitoba.ca.