Four genes found on the same chromosome are represented by R, S, T and U - VCE - SSCE Biology - Question 9 - 2005 - Paper 1
Question 9
Four genes found on the same chromosome are represented by R, S, T and U.
The percentage recombination between the genes is:
R-T, 7%
S-T, 37%
S-R, 30%
R-U, 20%
T-U,... show full transcript
Worked Solution & Example Answer:Four genes found on the same chromosome are represented by R, S, T and U - VCE - SSCE Biology - Question 9 - 2005 - Paper 1
Step 1
Identify the gene pairs and recombination frequencies
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Answer
The recombination frequencies given are:
R-T: 7%
S-T: 37%
S-R: 30%
R-U: 20%
T-U: 13%
These values indicate how close or far apart the genes are on the chromosome.
Step 2
Analyze the lowest recombination frequency
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Answer
R-T has the lowest recombination frequency of 7%, indicating R and T are closest together. This suggests they are adjacent on the chromosome.
Step 3
Determine the position of other genes
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Next, consider S with a recombination frequency of 30% to R. Since it is higher than R-T, S must be positioned further from R. Given the 37% between S and T, S can fit between R and T. The remaining gene, U, needs to be positioned according to the other frequencies, especially 20% (R-U) and 13% (T-U).
Step 4
Construct the final gene order
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To maintain the lowest recombination frequencies sequentially, the order would be R, S, T, U. This aligns with the recombination frequencies given, confirming that the sequence of the genes along the chromosome must be:
