**2.5 Inherit characteristics**

*The Recent Topics in Genetic Polymorphisms*

female babies) [30, 31].

**Figure 3.**

**2.4 Human genes and genetics**

are present, while in male, one X copy and one Y copy in their body cells. In female, 22 autosomes paired chromosomes in addition to X sex chromosome present in the egg cells, while in male, the same number of chromosomes are present and the difference only X or Y chromosome in their sperm cells. The combination egg with sperm gives 46 chromosomes regarding the sex chromosome (XY in male and XX in

*Distribution of gene in the chromosome within human cell from U S National Library of Medicine, National* 

*Institutes of Health, Department of Health & Human Services. June 4, 2012.*

The whole DNA in the cell makes a genome which contains both the exon (coding regions) and intron (non-coding region) that represent large sequences that do not encode any protein and their function is exactly not known yet [32, 33]. In genome, the gene is a basic biological functional unit of heredity that contributes to phenotype/function. A segment of DNA that encodes instruction is needed for a certain protein or enzyme. In other side, a lot of genes do not encode any protein. Only a fraction of DNA of the gene in the cell is expressed through transcription process that involves copy of chemical bases into messenger RNA (mRNA) in order to produce protein according to central dogma [33]. After that it will be translated by using ribosomes organelles, and mRNA migrates toward cytoplasm from nucleus to create polypeptide that folds in a certain configuration to make the protein. A range of human genes are between hundred to more than two millions of nitrogen bases. About 20,000–25,000 genes are located on the 23 pairs of chromosomes within nucleus according to human genome project [34]. The human genome project completed officially in April 2003, and only 12,800 genes and numerous other genes have been well mapped to loci on each of the chromosomes. On the other

In human being, any individual has two copies from each gene, one copy comes from father and second copy comes from mother [32]. In all people, most genes are similar, excluding small number of genes that are little a bit diverse between people (<1%). The alternative form of a gene that occurs at the same locus on homologous chromosomes called allele bears a small variation in their DNA sequences and participates to every person's single physical features. A single allele for each gene is inherited from each parent (e.g., at a locus for hair or eye color and blood type). About 2% only of genome represent the DNA in genes and full information is stored

hand, the correct number of human gene is still unknown [35, 36].

in a database that is publicly accessible [37].

**4**

Genes are considered as building blocks of inheritance [38]. The traits pass from parents to their offspring and are controlled by some genes; these are carried out by either sexual or asexual reproduction [39]. The genetic information and characteristics are acquired in the progeny cells from their natural parents. However, most of them are affected by mixing the environmental effect and genes. Many traits are observed simply like tongue rolling, dimples, freckles, hands clasping, etc. [40].
