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Question: Gregor Mendel’s discovery of basic hereditary principles was not realized until the early 20th century. Who were the scientists who rediscovered his work?
Answer: Hugo de Vries, Dutch botanist and geneticist, introduced the experimental study of organic evolution. In 1900 he rediscovered, simultaneously with the botanists Carl Correns and Erich Tschermak von Seysenegg, Gregor Mendel’s principles of heredity.
Question: Who provided the first conclusive evidence, in 1902, that chromosomes carry the units of inheritance and occur in distinct pairs?
Answer: Walter Sutton, an American geneticist, provided the first conclusive evidence that chromosomes carry the units of inheritance and occur in distinct pairs. Published in 1902, “On the Morphology of the Chromosome Group in Brachystola magna” provided the earliest detailed demonstration that the somatic chromosomes (those in cells other than sex cells) of a grasshopper occur in definite, distinguishable, and different pairs of like (or homologous) chromosomes. The paper ended with the hypothesis that chromosomes carry the units of inheritance.
Question: Who first identified individual genes by studying the giant chromosomes in the salivary gland cells of fruit flies?
Answer: Theophilus Shickel Painter, an American zoologist and cytologist, first identified individual genes in the chromosomes of fruit flies. Painter realized that the unusually large chromosomes in the salivary gland cells of Drosophila fruit flies are particularly well suited for studies of genes and chromosomes.
Question: In 1944 which American biologist, along with Oswald T. Avery and Colin M. MacLeod, used bacteria to provide the first experimental evidence that the genetic material of living cells is composed of DNA?
Answer: Maclyn McCarty was the American biologist who, with Oswald T. Avery and Colin M. MacLeod, provided the first experimental evidence that the genetic material of living cells is composed of deoxyribonucleic acid (DNA).
Question: Who deduced that the sex of an individual is determined by a particular chromosome?
Answer: Nettie Maria Stevens, an American biologist and geneticist, was one of the first scientists to find that sex is determined by a particular chromosome. In 1905, after experiments with the yellow mealworm, she published a paper in which she announced her finding that a particular combination of the chromosomes known as X and Y were responsible for the determination of the sex of an individual.
Question: Who laid the mathematical foundation of the science of genetics?
Answer: The Austrian botanist and plant experimenter Gregor Mendel theorized that the occurrence of the visible alternative characters of the plants, in the constant varieties and in their descendants, is due to the occurrence of paired elementary units of heredity, now known as genes. The novel feature of Mendel’s interpretation of his data was his recognition that genes obey simple statistical laws.
Question: Who laid the foundation for James Watson and Francis Crick to suggest the helical structure of DNA?
Answer: The British scientist Rosalind Franklin contributed to the discovery of the molecular structure of deoxyribonucleic acid (DNA), which serves to encode genetic information. She is credited with discoveries that established DNA’s helical conformation, as subsequently suggested by James Watson and Francis Crick.
Question: Which of these congenital disorders is characterized by an extra chromosome?
Answer: Down syndrome is a congenital disorder caused by an extra chromosome (trisomy) on the chromosome 21 pair.
Question: How many pairs of chromosomes are found in the human body?
Answer: Humans have 23 pairs of chromosomes.
Question: Who discovered the sex-determining chromosome?
Answer: American zoologist Clarence E. McClung’s study of the mechanisms of heredity led to his 1901 hypothesis that an extra, or accessory, chromosome was the determiner of sex. The discovery of the sex-determining chromosome provided some of the earliest evidence that a given chromosome carries a definable set of hereditary traits.
Illustrated strands of DNA. Deoxyribonucleic acid, biology.

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