Heredity and Evolution Test - 9

DNA isolation is a process of purification of DNA from sample using a combination of physical and chemical methods. The first isolation of DNA was done in 1869 by Friedrich Miescher.

August Weismann (1834-1914) was a neo-Darwinian biologist who proposed the germplasm theory in his book Das Keimplasma.

He said that variations are of two types. Some are congenital i.e., organisms are born with them. Others are acquired during the life time of a particular plant or animal. It was with this latter type of variations, the acquired characters, that Weismann was very much concerned. He gradually developed his Theory of Germplasm to explain that acquired characters could not be inherited.

Eukaryotic chromosome typically contains 2 copies of each gene and is therefore genetically diploid. The diploid eukaryotic genome is halved to haploid via the process called meiosis.

Hugo de Vries in his book Die Mutation Theory (1901) proposed the mutation theory in order to explain the mechanism of evolution.

This theory was based on his observations on evening primrose, Oenothera lamarckiana. He studied this plant in wild forms for many years continuously and observed certain spontaneous changes in some of these wild plants. These plants differed considerably in stem height, flower colour and leaves shapes. He observed that these changes were heritable and ultimately led to several new varieties.

A GMO (genetically modified organism) is the result of a laboratory process where genes from the DNA of one species are extracted and artificially forced into the genes of an unrelated plant or animal. The foreign genes may come from bacteria, viruses, insects, animals or even humans.

Punnett's gametic checkerboard method is of great use in deducting the genotype and phenotype of the F2 offsprings of a hybridization cross. The gametic checkerboard has the equal number of squares in horizontal and vertical lines according to the number of gametic combinations of F1 hybrid.

Backcrossing is a crossing of a hybrid with one of its parents or an individual genetically similar to its parent, in order to achieve offspring with a genetic identity which is closer to that of the parent. It is used in horticulture, animal breeding and in production of gene knockout organisms.

Paleontologists view Archaeopteryx as a transitional fossil between dinosaurs and modern birds. With its blend of avian and reptilian features, it was long viewed as the earliest known bird. Discovered in 1860 in Germany, it's sometimes referred to as Urvogel, the German word for "original bird" or "first bird." Recent discoveries, however, have displaced Archaeopteryx from its lofty title.

Mutation causes sudden change in gene sequences causing new phenotype.

Change in genotype and phenotype conclusively  is termed as variation.

Gregor Mendel, through his work on pea plants, discovered the fundamental laws of inheritance. He deduced that genes come in pairs and are inherited as distinct units, one from each parent. Mendel tracked the segregation of parental genes and their appearance in the offspring as dominant or recessive traits.