Question

The term ‘’linkage’’ was coined by
A. T.H. Morgan
B. T. Boveri
C. G. Mendel
D. W. Sutton

Answer 1

Linkage is defined as the association of genes or DNA sequences located on the same chromosome and inherited together. It is the close co-location of genes or of DNA variations to each other. Due to this the alleles, or gene versions, already together on one chromosome get inherited as a unit.

Complete answer:
Genetic linkage describes the way during which two genes that are located on the brink of one another on a chromosome are often inherited together. The existence of linkage groups is the reason some traits don't suit Mendel’s law of independent assortment (recombination of genes and therefore the traits they control); i.e., the principle applies as long as genes are located on different chromosomes. Variation within the gene composition of a chromosome can occur when a chromosome breaks, and therefore the sections join with the partner chromosome if it's broken in equivalent places. This exchange of genes between chromosomes, called linkage, usually occurs during meiosis, when the entire number of chromosomes is halved.
When genes are on the same chromosome but very far apart, they assort independently due to crossing over. Crossing over puts new alleles together in combination on the same chromosome, causing them to go into the same gametes thus; all gametes are produced with a frequency of 25% each. On the other hand, when genes are very close together on the same chromosome, crossing over still occurs, but the genes stick together during meiosis and therefore, the genes are linked.
In 1911, T.H. Morgan, while studying heredity in fruit flies, observed the eye color of a fly was associated with the fly's sex and soon hypothesized that the two traits were linked together. These observations led to the concept of genetic linkage which further concluded that the closer two genes are to one another on a chromosome, the greater their chances are of being inherited together. However, genes that are located farther away from each other on the same chromosome are more likely to be separated during recombination, the process that recombines DNA during meiosis. The strength of linkage between two genes, therefore, depends upon the distance between the genes on the chromosome.

Therefore, the correct option is a, T.H. Morgan.

Note: Linkages generate parental types and increases in age because the linkage increases. Crossing over generates recombination and it decreases with age and therefore the occurrence of Linkage between two genes is decreased if they're placed closely, whereas the linkage strength between two genes increases if a chromosome is found within the vicinity. Linkages assist in maintaining a newly improved variety crossover.