Ho Huu Tho
Senior Member
#30.5
Genes Are Carried on Chromosomes
Long before the discovery that genes were made of DNA, geneticists realized that hereditary factors—genes—were carried on chromosomes. Unlike genes themselves, chromosomes can be easily seen under the microscope, and their movements can be followed during the processes of mitosis and meiosis. Beginning around 1910, Thomas Morgan and colleagues showed that the patterns of Mendelian inheritance could be correlated with the patterns of movement and recombination of the chromosomes. Morgan’s group showed that one of the central events of meiosis is crossing over, in which genes trade places between maternal and paternal chromosomes. In this way, Morgan and colleagues developed the chromosomal theory of inheritance and gave a physical reality to the abstract concept of the gene.
<style>@font-face { font-family: "Cambria"; }@font-face { font-family: "JansonText-Roman"; }p.MsoNormal, li.MsoNormal, div.MsoNormal { margin: 0cm 0cm 10pt; font-size: 12pt; font-family: "Times New Roman"; }div.Section1 { page: Section1; }</style> From this point, much work was devoted to discovering the physical nature of the gene. Throughout the next several decades, a series of experiments showed that genes were made of DNA (deoxyribonucleic acid), and finally that the double-helical structure of DNA accounted for the faithful replication and inheritance of genes.
Genes Are Carried on Chromosomes
Long before the discovery that genes were made of DNA, geneticists realized that hereditary factors—genes—were carried on chromosomes. Unlike genes themselves, chromosomes can be easily seen under the microscope, and their movements can be followed during the processes of mitosis and meiosis. Beginning around 1910, Thomas Morgan and colleagues showed that the patterns of Mendelian inheritance could be correlated with the patterns of movement and recombination of the chromosomes. Morgan’s group showed that one of the central events of meiosis is crossing over, in which genes trade places between maternal and paternal chromosomes. In this way, Morgan and colleagues developed the chromosomal theory of inheritance and gave a physical reality to the abstract concept of the gene.
<style>@font-face { font-family: "Cambria"; }@font-face { font-family: "JansonText-Roman"; }p.MsoNormal, li.MsoNormal, div.MsoNormal { margin: 0cm 0cm 10pt; font-size: 12pt; font-family: "Times New Roman"; }div.Section1 { page: Section1; }</style> From this point, much work was devoted to discovering the physical nature of the gene. Throughout the next several decades, a series of experiments showed that genes were made of DNA (deoxyribonucleic acid), and finally that the double-helical structure of DNA accounted for the faithful replication and inheritance of genes.