3. A 2006 genetic study of a large American family attempted to identify genetic
ID: 58883 • Letter: 3
Question
3.
A 2006 genetic study of a large American family attempted to identify genetic linkage between DNA markers (A and B) to the gene producing the autosomal dominant disorder spinocerebellar ataxia type 5 (SCA5). The following data show the LOD scores obtained for each theta value in the analysis:
Theta value
0.01
0.05
0.10
0.20
0.30
0.40
SCA5 and marker A
11.02
12.26
11.94
10.04
7.26
3.77
SCA5 and marker B
0.35
0.94
1.07
0.99
0.75
0.43
i) What is the likely map distance between SCA5 and marker A?
a) 0.05 map units
b) 5 map units
c) 12.26 map units
d) the SCA5 gene and marker A are not linked based on this data
ii) What is the likely map distance between SCA5 and marker B?
a) 0.01 map units
b) 10 map units
c) 1.07 map units
d) the results for SCA gene and Mark B are not conclusive, more data is necessary to determine the linkage
Theta value
0.01
0.05
0.10
0.20
0.30
0.40
SCA5 and marker A
11.02
12.26
11.94
10.04
7.26
3.77
SCA5 and marker B
0.35
0.94
1.07
0.99
0.75
0.43
Explanation / Answer
* The distance between a gene and marker can be estimated from theta for which LOD score reaches a maximum positive value.
1. (c) 12.26 map units
2. (c) 1.07 map units
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