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Two gene loci in an organism have the following alleles - VCE - SSCE Biology - Question 15 - 2007 - Paper 1
Question 15
Two gene loci in an organism have the following alleles. Gene locus one : T and t Gene locus two : P and p An organism showing both dominant traits, but with unkno... show full transcript
Worked Solution & Example Answer:Two gene loci in an organism have the following alleles - VCE - SSCE Biology - Question 15 - 2007 - Paper 1
Step 1
An appropriate test cross to establish the genotype of such an organism would be
Answer
To determine the unknown genotype of an organism exhibiting both dominant traits (T-P-), we can perform a test cross with a homozygous recessive individual for both traits.
Given the options:
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A. T-P- x tt pp: This option is ideal because it involves crossing with an individual that is homozygous recessive for both alleles (t and p). This will allow us to observe the offspring and determine the genotype of T-P- based on the phenotypic ratios of the progeny.
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B. T-P- x Tt Pp: This option involves crossing with a heterozygous individual. While it can provide some information, it will not definitively reveal the genotype of T-P- as the offspring could display a mix of dominant and recessive traits.
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C. T-P- x TT PP: This option is not suitable since it crosses with a homozygous dominant individual which cannot provide information on the recessive alleles.
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D. T-P- x TT pp: While this option tests one locus (T), it fails to test the other locus (P) fully, therefore it is also not suitable.
Therefore, the correct answer is A. T-P- x tt pp.