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The diploid nature of chromosomes allows for genes on different chromosomes to assort independently during sexual reproduction, recombining to form new combinations of genes. Genes on the same chromosome would theoretically never recombine, however, were it not for the process of chromosomal crossover. During crossover, chromosomes exchange stretches of DNA, effectively shuffling the gene alleles […]
The molecular basis for genes is deoxyribonucleic acid (DNA). DNA is composed of a chain of nucleotides, of which there are four types: adenine (A), cytosine (C), guanine (G), and thymine (T). Genetic information exists in the sequence of these nucleotides, and genes exist as stretches of sequence along the DNA chain. Viruses are the […]
Organisms have thousands of genes, and in sexually reproducing organisms assortment of these genes are generally independent of each other. This means that the inheritance of an allele for yellow or green pea color is unrelated to the inheritance of alleles for white or purple flowers. This phenomenon, known as “Mendel’s second law” or the […]
At its most fundamental level, inheritance in organisms occurs by means of discrete traits, called “genes”.This property was first observed by Gregor Mendel, who studied the segregation of heritable traits in pea plants.In his experiments studying the trait for flower color, Mendel observed that the flowers of each pea plant were either purple or white […]
Francis Crick’s first sketch of a DNA double helix.
Molecular genetics
Although chromosomes were known to contain genes, chromosomes were composed of both protein and DNA — it was unknown which was critical for heredity or how the process occurred. In 1928, Frederick Griffith published his discovery of the phenomenon of transformation (see Griffith’s experiment); sixteen years […]
The modern science of genetics traces its roots to the observations made by Gregor Johann Mendel, a German-Czech Augustinian monk and scientist who made detailed studies of the nature of inheritance in plants. In his paper “Versuche über Pflanzenhybriden” (”Experiments on Plant Hybridization”), presented in 1865 to the Brunn Natural History Society, Gregor Mendel traced […]
Although the science of genetics has its origins in the work of Gregor Mendel in the mid-1800s, various theories of inheritance preceded Mendel. These theories generally assumed that there existed an inheritance of acquired characteristics: the belief that individuals inherit traits that have been strengthened in their parents. Today, the theory is commonly associated with […]
Genetics, a discipline of biology, is the science of heredity and variation in living organisms. Knowledge of the inheritance of characteristics has been implicitly used since prehistoric times for improving crop plants and animals through selective breeding. However, the modern science of genetics, which seeks to understand the mechanisms of inheritance, only began with the […]
