Ch.20 - BiotechnologyWorksheetSee all chapters
All Chapters
Ch.1 - Introduction to Biology
Ch.2 - Chemistry
Ch.3 - Water
Ch.4 - Carbon
Ch.5 - Biological Molecules
Ch.6 - Cells
Ch.7 - The Membrane
Ch.8 - Energy and Metabolism
Ch.9 - Respiration
Ch.10 - Photosynthesis
Ch.11 - Cell Signaling
Ch.12 - Cell Division
Ch.13 - Meiosis
Ch.14 - Mendelian Genetics
Ch.15 - Chromosomal Theory of Inheritance
Ch.16 - DNA Synthesis
Ch.17 - Gene Expression
Ch.18 - Regulation of Expression
Ch.19 - Viruses
Ch.20 - Biotechnology
Ch.21 - Genomics
Ch.22 - Development
Ch.23 - Evolution by Natural Selection
Ch.24 - Evolution of Populations
Ch.25 - Speciation
Ch.26 - History of Life on Earth
Ch.27 - Phylogeny
Ch.28 - Prokaryotes
Ch.29 - Protists
Ch.30 - Plants
Ch.31 - Fungi
Ch.32 - Overview of Animals
Ch.33 - Invertebrates
Ch.34 - Vertebrates
Ch.35 - Plant Anatomy
Ch.36 - Vascular Plant Transport
Ch.37 - Soil
Ch.38 - Plant Reproduction
Ch.39 - Plant Sensation and Response
Ch.40 - Animal Form and Function
Ch.41 - Digestive System
Ch.42 - Circulatory System
Ch.43 - Immune System
Ch.44 - Osmoregulation and Excretion
Ch.45 - Endocrine System
Ch.46 - Animal Reproduction
Ch.47 - Nervous System
Ch.48 - Sensory Systems
Ch.49 - Muscle Systems
Ch.50 - Ecology
Ch.51 - Animal Behavior
Ch.52 - Population Ecology
Ch.53 - Community Ecology
Ch.54 - Ecosystems
Ch.55 - Conservation Biology

Solution: A 13-nucleotide long DNA template was sequenced by the chain-terminator method (the Sanger method) using a 5'-TAG primer. The resulting fragments were analyzed by gel electrophoresis as shown below. In each of the four different gel lanes (or wells), a different ddNTP was used (i.e. ddATP for the 1st well, ddGTP for the 2nd, ddCTP for the 3rd, and ddTTP or the 4th).Determine the sequence of the DNA template strand.

Problem

A 13-nucleotide long DNA template was sequenced by the chain-terminator method (the Sanger method) using a 5'-TAG primer. The resulting fragments were analyzed by gel electrophoresis as shown below. In each of the four different gel lanes (or wells), a different ddNTP was used (i.e. ddATP for the 1st well, ddGTP for the 2nd, ddCTP for the 3rd, and ddTTP or the 4th).

Determine the sequence of the DNA template strand.

Solution

The Sanger method, or the chain-terminator method determines the sequence of the template strand by through the use of the DNA polymerase reaction while utilizing a small concentration of dideoxynucleoside triphosphates (ddNTPs). These ddNTPs attach to the elongating chain but cause a premature termination due to the lack of OH group in the 3' carbon. Subsequent electrophoresis would give the sequence provided by the differently sized fragments produced in the reactions.

By concept, the smallest fragment of the sequence should have traveled farthest in an electrophoretic profile. Thus, the first base added to the elongating chain is found at the bottom, which, in this case, is A. The sequence is then followed by two Gs, and so on.

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