“for sale” or “telephone number” and so on. A combinatorial method for gene prediction uses templates of previously sequenced genes to recognize newly sequenced genes.
1.10
Genetic engineering and human genomes
Genetic code, genetic engineering and the Human Genome Project (HGP) are discussed in this section.
1.10.1
Genetic code
The genetic code is the cellular alphabet that specifies one of the 20 common cellular amino acids or stop codons from the 64 triplets in messenger RNA [112].
A codon or triplet includes three nucleotides that are read by cellular machinery to specify an amino acid. Four nucleotides might make 64 possible combinations (43).
The sequence of nucleic acid in DNA is important because it codes the sequence of amino acid in proteins [83]. The relationship between the sequence of DNA and the se- quence of corresponding protein is called genetic code. The primary structure of a protein is a linear chain of building blocks called amino acids.
Genetic code is a cellular “conversion table” between codon and amino acid [112]. Of the 64 combinations, 61 are used to specify amino acids and the other 3 are known as stop codons which are genetic signals in the code that signal protein termination. [112]. See Table 1.1
1.10.2
Genetic engineering
Genetic engineering is a term for the process of manipulating genes, usually outside the organism’s natural reproductive process [131].
Genetic engineering works on the organism’s DNA. This happens by introducing a new gene from an organism of a totally different species. For this, scientists first select an organism with useful genes to create a desired feature. By using chemical ‘scissors’, they cut out the gene and insert it into the DNA of the other organism.
Recombinant DNA technology (or gene splicing) uses enzymes to cut and paste DNA into a “recombinant molecule” [112]. Since recombinant molecules spliced in the labora- tories are identical clones of each other, it is also known as cloning.
Background and Literature Review 1.10. Genetic engineering and human genomes
Second Position (Middle)
First Position (50) A G C T Third Position (30)
A lys arg thr lle A
lys arg thr met G asn ser thr lle C asn ser thr lle T
G glu gly ala val A
glu gly ala val G asp gly ala val C asp gly ala val T
C gln arg pro leu A
gln arg pro leu G his arg pro leu C his arg pro leu T
T stop stop ser leu A
stop trp ser leu G tyr cys ser phe C try cys ser phe T Table 1.1: The Genetic Code
1.10.3
Human Genome Project (HGP)
The genome defines the genetic construction of a cell or genotype [83]. Genotype is the genetic makeup of an organism, and the complete set of characteristics expressed by an organism is called its phenotype.
The genome of a cell consists of one or more molecules of DNA inside a chromosome. For bacteria the cell contains only one copy of the genetic material and is called haploid. Higher organisms have two copies and are called diploid.
Human genome project and its aims
The human genome is all the DNA in one set of chromosomes [131]. Fifty years after James Watson and Francis Crick found the structure of DNA in 1953, scientists researching the human genome succeeded in reading the sequence of bases in the DNA in human cells. A draft was published in 2000. They found the order of the“letters” A,T,C,G that compose the coded messages of genes. These coded messages determine how our body is assembled and how it works and shows if we are predisposed to suffer certain kind of diseases. The first aim of the human genome project is to find the precise sequence of bases in DNA that make up a genome. The second aim is to construct a complete map of genomes that will
Background and Literature Review 1.10. Genetic engineering and human genomes
show where the genes are located.
Human genome project importance
Sequencing of the human genome has been acclaimed as the greatest achievement in biol- ogy [101]. Completion of the human genome project is not the end of technology develop- ment related to DNA sequencing. There are many genomes to be sequenced and there are many individuals to be compared with the standard sequence.
The working draft of entire human genome, involved with the sequences of 85% to 90% of 3 billion DNA bases. This is the construction map of humans and has potential in the discovery of functional genes, distinguishing gene mutations responsible for diseases and development of methods and procedures for detection, treatment and prevention of variety of diseases. One of the objectives of human genome project is clinical use of genomic in- formation. This might help pharmaceutical companies to produce medications compatible with the patient’s genetic profile to increase efficiency and effectiveness, and to decrease the side effects.
1.10.4
Structural and functional genomics
A branch of biology that studies the structure and function of genes is called genomics [5]. Structural genomics is the application of sequencing technologies to create representative genome sequences for different organisms, specially humans.
Functional genomics is the study of the functions of genes to understand the behaviour of all the genes in a genome. Knowing the sequence of a gene does not mean that its function is known as well.
1.10.5
Genome analysis
Cytogeneticsis the study of the structure of chromosomal material [101]. Biophysics is an interdisciplinary science that applies the theories and methods of physics to questions in biology. Biochemistry is the field of study that endeavours to understand the chemical basis of life by focusing on the study of DNA, RNA, proteins, and other biomolecules. Molecular biologyis the study of biology at a molecular level. The field overlaps with other areas of biology and chemistry, particularly genetics and biochemistry. All these disciplines have