Unique-sequence DNA

The DNA in a eukaryotic genome can be divided into different sequence classes. These are unique-sequence, or nonrepetitive, DNA and repetitive-sequence DNA. In the haploid genome, unique-sequence DNA generally includes the single copy genes that code for proteins. The repetitive DNA in the haploid genome includes sequences that vary in copy number from two to as many as 10 copies per cell. 

This estimation (and the distribution of repetitive-sequence DNA) is based on a variety of DNA-RNA hybridization techniques and, more recently, on direct DNA sequencing. Similar techniques are used to estimate the number of active genes in a population of unique-sequence DNA. In brewers yeast Saccha-romyces cerevisiae, a lower eukaryote), about two thirds of its 6200 genes are expressed. In typical tissues in a higher eukaryote (eg, mammalian liver and kidney), between 10,000 and 15,000 genes are expressed. Different combinations of genes are expressed in each tissue,... 

The genome of the domestic fowl comprises about 70% unique sequence DNA and 30% moderate and highly repetitive sequences (see Section 8.2) the question is how are these sequences organised on the... 

Exonuclease An enzyme that cleaves nucleotides from either the 3 or 5 ends of DNA or RNA. Fingerprinting The use of RFLPs or repeat sequence DNA to establish a unique pattern of DNA fragments for an individual. 

Every gene contains DNA with a unique sequence of bases forming a genetic code containing the information an organism uses to iive and repiicate itseif Many years of research have resuited in an understanding of how the information content of DNA is transiated into particuiar biochemicai substances and how DNA repiicates. The processes inciude unwinding of the DNA doubie heiix so its code can be read or dupiicated. 

In 1990, work was started to characterize the human genome which had been shown to consist of about 3 billion base pairs. The final result was announced in the year 2000. All of the chromosomes have been characterized. The human genome has been shown to contain some 30,000 genes (which are sections of the chromosome which code for specific proteins). Each cell produces the t T)e of proteins needed for it to function. The function of mRNA is to transfer information from the DNA. so as is to fix the limits of the protein needed. The vast majority of the proteins found in living organisms are composed of only 20 different kinds of amino acids, repeated many times and strung together in a particular order. Each type of protein has its own unique sequence of amino acids. This sequence, known as its primary structure, actually... 

All cells in living organisms contain the large nucleic acid molecules of ribonucleic acid (RNA) and deoxyribonucleic acid (DNA). Both these molecules are polymers of nucleotides. DNA is found in chromosomes, and genes are unique sequences of DNA nucleotides. The genes contain the inheritable information which together with RNA directs the synthesis of all the cell s proteins. 

DNA replication begins with protein binding to the origin of replication, a unique sequence in the bacterial chromosome, causing a short region of double-stranded DNA (dsDNA) to unwind (Figure 11-2). 

The amount of double-stranded DNA fragments required depends on the number of randomized nucleotides and on the expectation of how many times a unique sequence combination should be represented in the pool. Each extension of the randomized sequence by one nucleotide requires a fourfold increase of nucleic acid molecules [61]. Another important parameter is the transformation efficiency of the system used. 

Because a particular restriction enzyme recognizes a unique sequence, the number of cuts made in a DNA molecule is limited. Depending on the size of the... 

Synthesis of a specific DNA segment via the PCR is directed by two oligonucleotide primers. Multiple rounds of extension from the primers amplify the target sequence exponentially, with termini defined by the 5 ends of the two primers. This process allows the determination of sequences from a very small number of target molecules. Unique sequences can be amplified from a complex mixture of nucleic acids because of the high specificity of the primer-template hybridization. 

To grow and divide, cancer cells must duplicate their chromosomes which are composed of deoxynucleoside 5 monophosphates (dNMPs) polymerized in unique sequences. Cancers may differ from normal cells of the body by growing more rapidly and/or by cycling and dividing continuously. Inhibitors of nucleotide biosynthesis will have selective toxicity for such cancers due to a depletion or imbalance in the cellular levels of dNTPs required for DNA synthesis, which would be more pronounced than in normal cells. A selective depletion of one of the four dNTPs (e.g., dTTP) by treatment of cancer... 

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