Show Advanced Search


Containing Text
- - -
Filter by author or institution
Filter by publication date
October, 2006
Filter by journal section

Filter by science education

Self-Fertilization: The fusion of a male gamete with a female gamete from the same individual animal or plant.

Monohybrid Crosses

JoVE 10773

In the 1850s and 1860s, Gregor Mendel investigated inheritance by performing monohybrid crosses in pea plants. He crossed two plants that were true-breeding for different traits. Based on his observations, Mendel proposed that organisms inherit two copies of each trait, one from each parent, and that dominant traits can hide recessive traits. These results formed the basis of two fundamental principles in genetics: the Principle of Uniformity and the Law of Segregation. Over eight years spanning the 1850s and 1860s, an Austrian monk named Gregor Mendel carried out seminal breeding experiments with pea plants. These experiments demonstrated the fundamental principles of inheritance, earning him the moniker “the father of modern genetics.” Mendel’s experiments focused on seven pea plant characteristics, each manifesting as one of two traits that are determined by a single gene locus. Mendel noticed that, when some of his pea plants reproduced by self-fertilization, their progeny always displayed the same trait. In other words, they were true-breeding. For example, some plants with yellow pods only produced offspring with yellow pods. When crossed with other plants that bred true for yellow pods, these plants also produced only progeny with yellow pods. Similarly, Mendel observed true-breeding pea plants that produced only offspring with g

 Core: Classical and Modern Genetics

Frequency-dependent Selection

JoVE 10960

When the fitness of a trait is influenced by how common it is (i.e., its frequency) relative to different traits within a population, this is referred to as frequency-dependent selection. Frequency-dependent selection may occur between species or within a single species. This type of selection can either be positive—with more common phenotypes having higher fitness—or negative, with rarer phenotypes conferring increased fitness. In positive frequency-dependent selection, common phenotypes have a fitness advantage. This scenario is often seen in interactions where mimicry is involved. In the Neotropical region of Central America, the butterfly species Heliconius cydno and Heliconius sapho are involved in a Müllerian mimicry partnership. Both butterflies are black and white, a common aposematic signal in the animal kingdom that warns of toxicity, venom, bad taste, or other predator deterrents. Interestingly, H. cydno can hybridize with a closely related sister species, H. melpomene, and produce offspring. H. melpomene is predominantly black and red. The resulting mixed white-red-black hybrid offspring are significantly less fit. In addition to the female hybrids being sterile, predators do not recognize the colors as deterrent warnings, and butterflies of either parent species do not recognize

 Core: Natural Selection

C. elegans Development and Reproduction

JoVE 5110

Ceanorhabditis elegans is a powerful tool to help understand how organisms develop from a single cell into a vast interconnected array of functioning tissues. Early work in C. elegans traced the complete cell lineage and structure at the electron microscopy level, allowing researchers unprecedented insight into the connection between genes, development and disease. …

 Biology I

An Introduction to Caenorhabditis elegans

JoVE 5103

Caenorhabditis elegans is a microscopic, soil-dwelling roundworm that has been powerfully used as a model organism since the early 1970’s. It was initially proposed as a model for developmental biology because of its invariant body plan, ease of genetic manipulation and low cost of maintenance. Since then C. elegans has rapidly grown in popularity and is now utilized…

 Biology I

Genetic Crosses

JoVE 5541

To dissect genetic processes or create organisms with novel suites of traits, scientists can perform genetic crosses, or the purposeful mating of two organisms. The recombination of parental genetic material in the offspring allows researchers to deduce the functions, interactions, and locations of genes.

This video will examine how…

More Results...