Information strand

DNA contains sequences of bases known as promoter sites. The promoter sites mark the beginning of genes. An enzyme recognizes a promoter site and binds to it, initiating RNA synthesis. The DNA at a promoter site unwinds to give two single strands, exposing the bases. One of the strands is called the sense strand or informational strand. The complementary strand is called the template strand or... 

Problem 21.24. What is the relationship of the RNA synthesized from a portion of a DNA template strand to the corresponding portion of the DNA information strand ... 

The mutagen 5-bromouracil changes A-T pairs to G-C pairs or G-C pairs to A-T pairs. The mutation in (c) could be induced by 5-bromouracil. For example, the DNA sequence AAA, which codes for phenylalanine, could be changed to the sequence AAG, which codes for leucine. The other mutations could not arise from treatment with 5-bromouracil. Remember that the genetic code presented in the text is expressed in terms of RNA. The sequence UUU on RNA corresponds to the sequence AAA on the informational strand of DNA. Leucine is encoded by the sequence CUU on RNA, which corresponds to the sequence AAG on the informational strand of DNA. Remember also that, unless otherwise specified, nucleotide sequences are written in the 5 —> 3 direction. 

Cellular Protein Biosynthesis. The process of cellular protein biosynthesis is virtually the same in all organisms. The information which defines the amino acid sequence of a protein is encoded by its corresponding sequence of DNA (the gene). The DNA is composed of two strands of polynucleotides, each comprising some arrangement (sequence) of the four nucleotide building blocks of the nucleic acids adenine (A), thymine (T),... 

In principle, the Maxam-Gilbert method can provide the total sequence of a dsDNA molecule just by determining the purine positions on one strand and then the purines on the complementary strand. Complementary base-pairing rules then reveal the pyrimidines along each strand, T complementary to where A is, C complementary to where G occurs. (The analogous approach of locating the pyrimidines on each strand would also provide sufficient information to write the total sequence.)... 

The renaturation rate of DNA is an excellent indicator of the sequence complexity of DNA. For example, bacteriophage T4 DNA contains about 2 X 10 nucleotide pairs, whereas Escherichia coli DNA possesses 4.64 X 10 . E. coli DNA is considerably more complex in that it encodes more information. Expressed another way, for any given amount of DNA (in grams), the sequences represented in an E. coli sample are more heterogeneous, that is, more dissimilar from one another, than those in an equal weight of phage T4 DNA. Therefore, it will take the E. coli DNA strands longer to find their complementary partners and reanneal. This situation can be analyzed quantitatively. 

The two strands which make up DNA are held together by hydrogen bonds between complementary pairs of bases adenine paired with thymine and guanine paired with cytosine. The integrity of the genetic code (and of life as we know it) depends on error-free transmission of base-pairing information. 

Transcription (Section 28.4) The process by which the genetic information encoded in DNA is read and used to synthesize RNA in the nucleus of the cell. A smal I portion of double-stranded DNA uncoils, and complementary ribonucleotides line up in the correct sequence for RNA synthesis. 

Messenger RNA (mRNA) is the intermediate template between DNA and proteins. The information from a particular gene is transferred from a strand of DNA by the construction of a complementary strand of RNA through a process known as transcription. The amount of any particular type of mRNA in a cell reflects the extent to which a gene has been expressed . 

The multiprotein unit that synthesize RNA by copying the sequence information from the leading strand of the DNA. Its activity is tightly controlled by phosphorylation of the C-termal domain (CTD), access to DNA and interaction by general and sequence specific transcription factors and coactivators and corepressors. 

The presented results and the additional information taken from various references indicate the direct relevance of the size of the network strands for the crack opening displacement and consequently for the toughness of the polymer. In polymers under load, the molecular chains at the tip of the crack break after the deformation zone ahead of the crack has grown to a critical width 5C, that is the crack opening displacement. This value 5C is proportional to the length of the molecular strands of the network and is linked in this way to the molecular structure of the polymer. However, the molecular mechanism for chain breakage in the deformation zone is not known at present. 

The amplification of genetic information, i.e., the replication of parent DNA molecules, is achieved by means of an entire set of enzymes. The major players are a DNA-gyrase for unwinding of the double helix, proteins to separate the two antiparallel DNA strands at the replicational junction, single-stranded binding proteins (SSB) that prevent the... 

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