Varying concentrations of a signaling molecule activate different transcription factors and determine cell fate.
Myosin II is one of the molecules involved in furrow formation in dividing cells. This animation shows how the molecule operates, and how furrowstatin blocks the mechanism and halts division of a cell.
DNA's chemical properties can be harnessed for a variety of biotechnology applications.
Adenine (A), cytosine (C), guanine (G), and thymine (T) are the components of nucleic acid that make up DNA.
In 1950, Erwin Chargaff published a paper stating that in the DNA of any given species, the ratio of adenine to thymine is equal, as is the ratio of cytosine to guanine. This became known as Chargaff's ratio, and it was an important clue for solving the structure of DNA.
Chronic myeloid leukemia (CML) is caused by a mutation that leads to an abnormal protein that is always active. The drug Gleevec has a shape that fits into the active site of the abnormal protein and stops its harmful effects.
Reactive molecules, such as free radicals, and solar ultraviolet radiation can lead to mutations in DNA. Most mutations are corrected, but in rare cases mutations can accumulate and cause diseases such as cancer.
DNA has a double helix structure. If untwisted, DNA looks like two parallel strands. Each strand has a linear sequence of A, C, G, and T. The precise order of the letters carries the coded instructions. One strand is a complementary image of the other: A always pairs with T, and C always pairs...
One of the failed hypothetical models of DNA is Linus Pauling's triple helix model. This structure would be unstable under normal cellular conditions.
Polymerase chain reaction, or PCR, is a technique for making many copies of a specific DNA sequence. DNA is repeatedly heated and cooled in the presence of primers that bracket the desired sequence and of the enzyme Tac polymerase. In as few as 30 cycles, a billion copies of the target sequence...
The structure of DNA, discovered by James Watson and Francis Crick, suggests a mechanism of replication. The double helix unwinds, and each strand acts as a template for the construction of the new DNA molecule.
Using information from molecular research, this 3-D animation shows how DNA is replicated at the molecular level. It involves an enzyme that unwinds the DNA, and other enzymes that copy the two resulting strands.
Both strands of the DNA double helix act as templates for the new DNA strands. Incoming DNA is unraveled by the enzyme helicase, resulting in the 3' strand and the 5' strand. The 3' strands and the 5' strands are replicated by a DNA polymerase enzyme but in different ways.
The first phase of the process of reading DNA information to make proteins starts with a molecule unzipping the DNA. The molecule then copies one of the strands of DNA into a strand of RNA, a close cousin of DNA. This process is called transcription.
The process of copying DNA into messenger RNA (mRNA) is called transcription. Transcription factors assemble at the promoter region of a gene, bringing an RNA polymerase enzyme to form the transcription initiation complex. Activator proteins at the enhancer region of DNA then activate the...
During the process of trying to elucidate the structure of DNA, Jim Watson made some cardboard models to try to understand how DNA nucleotides are paired. It helped him visualize how hydrogen atoms of paired nucleotides interact with each other to form a symmetrical structure that fits the...
Gleevec is a drug designed to interfere with the stimulation of growth in leukemia cells. This 3D animation shows how this is achieved.
The lactase enzyme is produced in the small intestine of infants. It digests lactose by breaking it into glucose and galactose.
Some cone snail toxins chemically hyperactivate neurons and immobilize prey, much like a Taser.
A single transcription factor controls this operon, which contains five genes necessary to produce bioluminescence.
Quorum sensing signal molecules have parts that are common between species as well as species-specific parts.
Listen to past HHMI President Dr. Thomas Cech discussing his Nobel Prize-winning discovery of RNA's catalytic properties.
The quorum sensing system is a target for a new class of drugs that interfere with virulence without killing bacteria.
In four lectures, Nobel laureate Thomas R. Cech, PhD, discusses the ability of RNA to act as more than just an intermediary between DNA and proteins.
Cellular enzymes are catalysts that tame reactions by accelerating them, lending specificity, and regulating their time and place.