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  • Film Guides: The Double Helix

    Film Guides: The Double Helix

    Film Guide

    The following classroom-ready resources complement The Double Helix. This short film describes the evidence that led James Watson and Francis Crick to the discovery of the double-helical structure of DNA and how the structure immediately revealed how genetic information is stored and inherited.

  • The Double Helix

    The Double Helix

    Short Film

    (16 min 53 sec) The Double Helix is the story of the scientists and evidence involved in one of the most important scientific quests of the 20th century: the discovery of the structure of DNA. Also available in Spanish.

  • Teacher Guide: DNA

    Teacher Guide: DNA

    Teacher Guide

    Topics include: DNA structure and function, DNA replication, damage to DNA and eukaryotic chromosomal structure.

  • The Chemical Structure of DNA

    The Chemical Structure of DNA

    Animation

    (2 min 44 sec) DNA's chemical properties can be harnessed for a variety of biotechnology applications.

  • Watson constructing base pair models

    Watson constructing base pair models

    Clip

    (1 min 42 sec) 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 double helix model.

  • DNA transcription (advanced detail)

    DNA transcription (advanced detail)

    Animation

    (1 min 55 sec) 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 transcription initiation complex. RNA polymerase unzips a small portion of the DNA and copies one strand into an mRNA molecule. Also available in Spanish.

  • DNA transcription (basic detail)

    DNA transcription (basic detail)

    Animation

    (1 min 55 sec) 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. Also available in Spanish.

  • Sanger method of DNA sequencing

    Sanger method of DNA sequencing

    Animation

    (52 sec) Fred Sanger developed the first technique for sequencing DNA. DNA is replicated in the presence of chemically altered versions of the A, C, G, and T bases. These bases stop the replication process when they are incorporated into the growing strand of DNA, resulting in varying lengths of short DNA. These short DNA strands are ordered by size, and by reading the end letters from the shortest to the longest piece, the whole sequence of the original DNA is revealed.

  • DNA replication (advanced detail)

    DNA replication (advanced detail)

    Animation

    (2 min 20 sec) 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. Also available in Spanish.

  • DNA replication (basic detail)

    DNA replication (basic detail)

    Animation

    (1 min 7 sec) 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. Also available in Spanish.

  • DNA replication (schematic)

    DNA replication (schematic)

    Animation

    (50 sec) 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. Also available in Spanish.

  • Paired DNA strands

    Paired DNA strands

    Animation

    (1 min 18 sec) 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 with G.

  • DNA packaging

    DNA packaging

    Animation

    (1 min 44 sec) DNA is tightly packed in the nucleus of every cell. DNA wraps around special proteins called histones, which form loops of DNA called nucleosomes. These nucleosomes coil and stack together to form fibers called chromatin. Chromatin in turn forms larger loops and coils to form chromosomes.

  • Damage to DNA leads to mutation

    Damage to DNA leads to mutation

    Animation

    (1 min 7 sec) 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.

  • Coding sequences in DNA

    Coding sequences in DNA

    Animation

    (1 min 5 sec) Of the 3 billion letters in the human genome, only 1% directly code for proteins. Of the rest, about 25% make up genes and their regulatory elements. The functions of the remaining letters are still unclear.

  • Chargaff's Ratio

    Chargaff's Ratio

    Animation

    (49 sec) 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.

  • Building blocks of DNA

    Building blocks of DNA

    Animation

    (27 sec) Adenine (A), cytosine (C), guanine (G), and thymine (T) are the components of nucleic acid that make up DNA.

  • Mismatch Repair

    Mismatch Repair

    Animation

    (1 min 22 sec) This animation illustrates how mistakes made during DNA replication are repaired.

  • RNA Folding

    RNA Folding

    Animation

    (33 sec) Since RNA is single-stranded, it can fold upon itself and form structures that are protein-like in both appearance and functionality.