From the 2011 Holiday Lectures — Bones, Stones, and Genes: The Origin of Modern Humans

Lactose Digestion in Infants

The lactase enzyme is produced in the small intestine of infants. It digests lactose by breaking it into glucose and galactose.

52 seconds

Natural Selection of Lactose Tolerance

Environmental and cultural factors can affect whether a new human mutation becomes common in a population.

46 seconds

Regulation of Eukaryotic DNA Transcription

General transcription factors, activators, and repressors interact to regulate the transcription of eukaryotic DNA into RNA.

2 minutes 6 seconds

From the 2005 Holiday Lectures — Evolution: Constant Change and Common Threads

Fossil Record of Stickleback Evolution

A quarry site in Nevada carries the evolutionary history of a population of stickleback fish that resided there when it was a freshwater lake. In a short time span in evolutionary terms—about 10,000 years—the fish population can be seen to dramatically reduce the size of their pelvic spines. This particular fossil record is remarkably complete with nearly year-by-year detail which includes documentation of intermediate forms.

1 minute 26 seconds

Gene Switch

Regulatory "switches" are found upstream from a gene. Regulatory molecules bind to the switches and recruit RNA polymerase to bind to the gene's promoter region, increasing the transcription of the gene into messenger RNA.

1 minute 14 seconds

Pitx1 Expression

In the stickleback fish, pelvic-fin reduction resulted from changes in the regulatory switch elements of the Pitx1 gene. In the marine ancestor, the Pitx1 gene is activated in the pelvic-fin region during development to generate the fin. In the pelvic-reduced stickleback, the regulatory switch that normally turns on the Pitx1 gene is either missing or non-functional.

54 seconds

Paintbrush Gene

In two related Drosophila species, a so-called paintbrush gene is activated to "paint" the pigment on the body. In one species, an extra switch activates the gene, resulting in spotted wings.

49 seconds

Pocket Mouse and Predation

The rock pocket mouse is found in two color variants, or morphs: light and dark. In different environments, their visibility to predators such as owls varies. The dark morph is more vulnerable on light sandy desert, and the light morph on dark lava rock.

20 seconds

Pocket Mouse Evolution

This simulation shows the spread of a favorable mutation through a population of pocket mice. Even a small selective advantage can lead to a rapid evolution of the population.

1 minute 4 seconds

Stickleback CT Scan

This animation shows a rotating 3-D image of a stickleback skeleton. The pelvic region, including the pelvic spines, is highlighted in red. Armored plating covers the flanks of the fish. The three prominent dorsal spines give the fish its name.

37 seconds

Wing Morph

This "morph" animation demonstrates how the expression of a particular toolkit gene in a butterfly larva corresponds to the location of the wing eyespots in an adult butterfly.

28 seconds