A planet is inhabited by creatures that reproduce with the same hereditary patterns seen in humans. Three phenotypic characters are height (T=tall, t=dwart), head appendages (A=antennae, a=no antennae), and nose morphology (S=upturned snout, s=downturned snout). Since the creatures are not 'intelligent,' Earth scientists are able to do some controlled breeding experiments using various heterozygotes in testcrosses. For tall heterozygotes with antennae, the offspring are tall antennae, 46; dwarf antennae, 7; dwarf no antennae, 42; tall no antennae, 5. For heterozygotes with antennae and an upturned snout, the offspring are antennae upturned snout, 47; antennae downturned snout, 2; no antennae downturned snout, 48; no antennae upturned snout, 3. Calculate the recombination frequencies for both experiments.

Verified step by step guidance

1. Identify the parental and recombinant phenotypes for each experiment. In the first experiment, the parental phenotypes are tall with antennae and dwarf with no antennae. The recombinant phenotypes are dwarf with antennae and tall with no antennae. In the second experiment, the parental phenotypes are antennae with upturned snout and no antennae with downturned snout. The recombinant phenotypes are antennae with downturned snout and no antennae with upturned snout.
2. Calculate the total number of offspring for each experiment. For the first experiment, add 46 (tall antennae) + 7 (dwarf antennae) + 42 (dwarf no antennae) + 5 (tall no antennae) to get a total of 100 offspring. For the second experiment, add 47 (antennae upturned snout) + 2 (antennae downturned snout) + 48 (no antennae downturned snout) + 3 (no antennae upturned snout) to get a total of 100 offspring.
3. Calculate the number of recombinant offspring for each experiment. In the first experiment, add 7 (dwarf antennae) + 5 (tall no antennae) to get 12 recombinant offspring. In the second experiment, add 2 (antennae downturned snout) + 3 (no antennae upturned snout) to get 5 recombinant offspring.
4. Calculate the recombination frequency for each experiment by dividing the number of recombinant offspring by the total number of offspring and then multiplying by 100 to convert to a percentage. For the first experiment, (12 recombinant / 100 total) * 100 = 12%. For the second experiment, (5 recombinant / 100 total) * 100 = 5%.
5. Interpret the results. The recombination frequencies of 12% and 5% indicate the degree of linkage between the genes. Lower percentages suggest closer linkage between the genes involved.

Key Concepts

Mendelian Genetics

Mendelian genetics is the study of how traits are inherited through generations based on the principles established by Gregor Mendel. It involves understanding dominant and recessive alleles, genotype versus phenotype, and the segregation and independent assortment of alleles during gamete formation. This framework is essential for analyzing inheritance patterns in the described breeding experiments.

Recombination Frequency

Recombination frequency is a measure of the likelihood that two genes will be separated during meiosis due to crossing over. It is calculated by dividing the number of recombinant offspring by the total number of offspring, providing insight into the genetic linkage between traits. Understanding this concept is crucial for interpreting the results of the breeding experiments and determining the genetic distance between the traits studied.

Testcross

A testcross is a breeding experiment used to determine the genotype of an individual exhibiting a dominant phenotype. By crossing the individual with a homozygous recessive partner, researchers can observe the phenotypes of the offspring to infer the unknown genotype. This method is particularly relevant in the context of the question, as it allows scientists to analyze the inheritance patterns of the creatures' traits.