DNA base code

Table 6.1 Different Effects of Small Changes to the DNA Base Code...

Triplet code—The arrangement of the genetic code such that three DNA bases code for one amino acid. 

Starting in his childhood in England, Francis Crick developed a fascination with science. After his collaborative work on DNA with James Watson, for which the two received a Nobel Prize, Crick unraveled the mystery of how DNA bases code for the primary sequence of a protein, and in 1957 he introduced its central dogma. Since 1976 Crick has been studying the functions of the human brain. 

Human brain natriuretic peptide (BNP) is a small peptide of 32 amino acids used in the treatment of congestive heat failure. How many nitrogen bases are present in the DNA that codes for BNP ... 

Intron DNA base sequence between exons, the protein-coding parts of a DNA sequence of a gene. Intronic sequences are transcribed into mRNA but they are spliced out of the RNA molecule before translation of RNA into protein (see also exon). 

Expressed Sequence Tags and In Silico Methods Expressed sequence tags (ESTs) are short nucleotide sequences of complementary DNA with about 200-500 base pairs. They are parts of the DNA that code for the expression of particular proteins. EST sequencing provides a rapid method to scan for all the protein coding genes and to provide a tag for each gene on the genome. 

In DNA molecules, the genetic code is represented by sequences of the four nucleotide bases adenine (A), cytosine (C), guanine (G) and thymine (T). On transcription, each template DNA base is represented in the equivalent mRNA by its complementary base thus ... 

All eukaryotic cells in our bodies contain the same 23 chromosomes with the same DNA base sequences. The lone differences are the mitochondria. The mitochondria in typical somatic cells contain less than 0.1% of the cell s DNA but in fertilized and dividing egg cells this number is greater. mtDNA is much smaller, often containing fewer than 20,000 base pairs. The value for humans is 16,569 base pairs. The mtDNA is a circular duplex. mDNA codes for the mitochondrial tRNAs and rRNAs but only a fraction of the mitochondrial proteins. Over 95% of the mitochondrial proteins are encoded by nuclear DNA. The mitochondria divide when the cell divides. 

Genetic code The hereditary information passed from generation to generation and found in the order of nitrogen bases in DNA the code controls protein synthesis in the organism. 

Transcription Transcription is the process of forming a complementary m-RNA strand from the DNA. This process occurs in the cell nucleus. To begin, an enzyme helps the DNA double helix to break apart and uncoil slightly. This allows RNA nucleotide bases to form complementary hydrogen bonds to the DNA bases. In essence, the m-RNA is reading the DNA code. For example, let s imagine a short section of DNA with the following sequence ... 

All the cells in the human body contain a complete copy of the approximately 3 billion DNA base pairs that make up the human genome. With its four-letter code, DNA contains all the information needed to build the entire human body Among the first genomes to be mapped were that of the chimpanzee, mouse, rat, pufferfish, fruit fly, roundworm, bakers yeast, and the bacterium Escherichia coli. As of 2008, the genomes of some 100 species genomes are completely known. 

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