Are the three genes in coupling or in repulsion? Clearly define if in coupling or repulsion for each gene in pairwise combination.
The three genes in coupling are in repulsion.
Coupling vs. Repulsion in Genetic Inheritance
Genetic inheritance involves the passing down of traits from parents to offspring through the transmission of genes. In this case, the three recessive traits in stickleback fish, including small body (nb), short spines (Is), and amoral, are inherited through linked genes on the same chromosome. The concept of coupling and repulsion plays a crucial role in understanding how these genes interact and are passed on.
Coupling:
Coupling occurs when two genes are on the same chromosome and tend to be inherited together. In the context of the traits observed in stickleback fish, coupling would mean that the genes for small body (nb), short spines (Is), and amoral are located close together on the same chromosome. When coupling is present, the dominant and recessive alleles for each gene are on the same chromosome.
In the given data, the genes nb and ls are in coupling, indicating that the alleles for these traits are inherited together. This implies that if an individual has the dominant allele for small body (nb+) and short spines (ls+), they are likely to be passed on together in the offspring.
Repulsion:
Repulsion, on the other hand, occurs when two genes are on homologous chromosomes and the dominant and recessive alleles are separated. In this case, one chromosome carries the dominant alleles for one trait, while the other chromosome carries the recessive alleles.
In the context of the stickleback fish traits, the genes nb and Is are in repulsion with respect to the gene a. This means that small body (nb) and short spines (Is) are inherited separately from amoral (a). Individuals who carry the dominant alleles for nb and Is may not necessarily carry the dominant allele for amoral.
Understanding the concepts of coupling and repulsion in genetic inheritance provides insights into how traits are passed on and inherited in offspring. By analyzing the patterns of inheritance and gene linkage, researchers can decipher the mechanisms of genetic variability and evolution in populations.