Sequence repeats, type

A. Fixed Length and Exact Sequence Repeats (Type A Repeat). 13... 

Copolymers are built from the repetition of two (or more) "repeat units". Depending on the spatial arrangement of those units (e.g., A and B) along the chain (sequencing), various types of copolymers can be made alternating, block, random (or statistical), branched, crosslinked (see Figure 12). 

Potato type II (Potll) inhibitors are disulfide-rich peptides of approximately 50 amino acids in size. They were first discovered in leaves, seeds, and other organs of Solanaceae and are a source of much interest as plant defense proteins. Recently, Barta et analyzed expressed sequence tag (EST) and genomic data and discovered 11 genes that code for Potll inhibitors in various monocotyledonous and dicotyledonous plants. Potll inhibitors are expressed as large precursor proteins that contain up to eight sequence repeats of the inhibitor precursor. In one particularly fascinating case from the ornamental tobacco (N. data), the precursor adopts a circular permuted structure.Barta et al. observed that genes outside the Solanaceae family seem... 

Fibrous protein sequences are often characterized by the presence of simple repetitive motifs. Some are exact in length and/or sequence, but others are only approximate and display considerable variation. Some motifs contain residues that are absolutely conserved in some positions, whereas in others it is only the sequence character that is maintained over the repeat length. In many fibrous proteins the repeats occur contiguously, whereas in others they are found widely separated in the sequence. The varieties of sequence repeat that have been observed are typed and catalogued here by Parry (Chapter 2). Each motif forms a discrete element of structure in many instances, these are arranged helically with respect to one another. In many cases an elongate structure is formed, and this can lead naturally to molecular aggregation and the formation of functional filaments. 

D. Nonintegral Repeats in Sequence Character (Type D Repeat). 14... 

A sequence repeat found in both fibrous and globular proteins is one in which a functional motif occurs, possibly several times in the sequence but often noncontiguously. This Type E repeat is exemplified by the Ca2+ EF hand, which is a length of sequence specifying a pair of a-helices that... 

Sequence repeats in proteins make use of structural and functional motifs that nature has found to work well in vivo. Large numbers of these motifs have now been characterized, and any newly determined amino acid sequence is generally run through computer databases to assess the number and type of repeats present, their possible conformations, and their likely functions in vivo. The characteristics of the sequence motifs... 

Screening of 10 patients for the dopamine D4 receptor (D4DR) gene polymorphism was used as a model system to demonstrate the capability of this device [14]. D4DR is the major receptor type in the limbic system. Its gene contains a 48-base-pair sequence repeat in exon 3 with a variable (twofold to eightfold) repeat number in individuals. This polymorphism is believed... 

A symbol of the type h, c, he, etc. obviously does not indicate the number of layers after which the sequence repeats, for this number is 2 for h (AB... ), 3 for c ABC.. . ), and 4 for he (ABCB.. .). The number of layers in the repeat unit of a particular stacking sequence may readily be found by deriving the latter from the symbol starting arbitrarily with AB. .. and continuing until the layer sequence repeats ... 

There are several major types of DNA sequence variation in the human genome. One type comprises repeated sequences with variations in the number of repeat units, such as short tandem repeat polymorphisms (STRPs, also known as microsatellites) in the form of mono-, di-, tri-, and tetra-nu-cleotide repeats, or more complex sequence repeats such as variable number tandem repeats (VNTRs) [2-4]. Repeat polymorphisms are relatively... 

By recent estimates, approximately 45% of the human genome is composed of repetitive sequences (repeated sequences of nucleotides). Although their significance is not understood, several types of repetitive sequences have been identified and investigated. There are two general classes tandem repeats and interspersed genome-wide repeats. Each is briefly described. 

Fig. 2. Three different construct-types are used for T-DNA- or transposon-mediated insertional mutagenesis in plants. A. The knock-out construct. B. The promoter-trap construct. C. The activator construct. The solid triangles indicate either the T-DNA border repeats or the sequence repeats at the ends of a transposable element.

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