Assignment 3

This assignment is worth 5% of the course grade. Due Nov. 19, 2024

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. Briefly explain your reasoning.

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?

Submitting your assignment

Make sure your assignment report includes your name, student number and UM email address.
Save your assignment report as a PDF file, and upload it to the PLNT3140 UMLearn dropbox site in the Assignment 3 folder. Files in word processing formats (.doc, .docx, .rtf, .odt) are NOT acceptable.

Note on grading: In assigning a grade, some consideration may be given to how the answer communicates your ideas. Keep in mind the following:

use of precise and appropriate biological terms
organization of ideas in your answer, so that a clear chain of logic is apparent. Formatting tools such as s subheadings or bullet points help to show the reader the structure of your ideas
ambiguity - Try to read your answers from the viewpoint of your reader. Are there several possible ways to interpret what you have said?
Feel free to use figures or tables in cases where they will be useful get across your ideas.

Note on academic integrity: The results in this assignment obviously are derived from the research literature. It will be considered a breach of academic integrity to search for the paper on the Internet and simply copy the author's conclusions from the paper.

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