**2. Genes in the cell**

Not each living cell of the human body have nucleus. Skin, hair, and red blood cells contain no nucleus [19, 20]. Nucleus contains a genetic material that is responsible for information. Half of these information of the genetic materials come from each parent [20].

#### **2.1 Chromosome**

All nuclei of human cell contain 23 pairs of small thread-like structures called chromosomes. Genes are localized within these 23 pairs chromosomes. About 23 out of 46 chromosomes come from the father and others like them come from the mother [21]. These chromosomes contain genes and some of them carry thousands of important genes while some carry only a few [22]. In addition to these, genes are made up of a chemical substance named deoxyribonucleic acid (DNA). The chromosomes are very long thread strands of DNA, coiled up tightly and compacted [23].

Along every chromosome, there is a constriction point called centromere, the numbering and divided packages of chromosome started from it [24]. The centromere separates the chromosome into two arms: long called "q arm" and short called "p arm" as in **Figure 1**. Chromosomes are numbered from 1 to 22 in both sexes and called autosomes, while the last one remaining take letters X and Y which are responsible for the gender. In female, X chromosome is duplicated, whereas Y chromosome is combined with X chromosome in male [24, 25] (**Figures 2** and **3**).

#### **2.2 Nitrogenous bases**

The nitrogenous bases are organic molecule with a nitrogen atom that bears chemical prosperities of a base and involves four letters in addition to fifth letter used in ribonucleic acid (RNA), and classified into two main compounds: pyrimidine cytosine (C), thymine (T), and uracil (U); and purine guanine (G) and adenine (A), respectively [27]. They were arranged in unique position in genes, which makes up combinations with permutations and combinations. It is worth mentioning (AT and GC) that bases pair is always found together, and there are different sequences

**3**

**2.3 Gender**

**Figure 2.**

*Genetic Polymorphisms*

**Figure 1.**

*DOI: http://dx.doi.org/10.5772/intechopen.88063*

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

of bases pairs in DNA coded messages [28]. These bases are part of DNA, and constitute a language when arranged together acting as a guide telling cells what need to

*Autosomes and sex chromosomes of Homo sapiens from US National Library of Medicine, National Institutes* 

Both gender have 46 paired chromosomes (44 autosomes), numbered from 1 to 22 chromosome pairs according to size, chromosome number 1 being the biggest one. In addition to autosomes, there are other two copies of sex chromosomes X and Y responsible for determination of gender. In female, two copies of X chromosome

do such as growing, division, maturity, and variety functions [29].

*Chromosome structure explained long and short arms [26].*

**Figure 1.**

*The Recent Topics in Genetic Polymorphisms*

stress, and diet, respectively [17, 18].

disorder [11, 12, 14, 15].

**2. Genes in the cell**

each parent [20].

**2.1 Chromosome**

**2.2 Nitrogenous bases**

increase incidence of disease, or prophylaxis from it [10]. Several disorders occur and arise from multiple factors such as genetic, lifestyle, and environmental [11]. Many previous studies revealed facts for the hereditability of main neuropsychiatric disorders, for example, depression, bipolar disorder, and schizophrenia [12, 13]. In all these behavioral disorders, a specific genetic fault is transported from parents to children and will enhance a progeny susceptibility risk of inheriting a specific

Neurological and mental diseases cannot be related to genetics science alone, so it is significant to seek implicated one's genetic composition material that possibly affects various direction of human behavior [16]. The relationship between genes and behavior leads to development of highly prevalent responses and disorders throughout a new biological factors. About 30–50% of the risk for anxiety and depression is genetic, while the other 50–70% of the risk may be attributed to environmental factors, such as substance use, stress, diet, and childhood experiences [17]. A comparison between genetic and environmental factors, demonstrated about 30–50% of the risk for anxiety and depression and 50–70% of substance uses,

Not each living cell of the human body have nucleus. Skin, hair, and red blood cells contain no nucleus [19, 20]. Nucleus contains a genetic material that is responsible for information. Half of these information of the genetic materials come from

All nuclei of human cell contain 23 pairs of small thread-like structures called chromosomes. Genes are localized within these 23 pairs chromosomes. About 23 out of 46 chromosomes come from the father and others like them come from the mother [21]. These chromosomes contain genes and some of them carry thousands of important genes while some carry only a few [22]. In addition to these, genes are made up of a chemical substance named deoxyribonucleic acid (DNA). The chromosomes are very long thread strands of DNA, coiled up tightly and compacted [23]. Along every chromosome, there is a constriction point called centromere, the numbering and divided packages of chromosome started from it [24]. The centromere separates the chromosome into two arms: long called "q arm" and short called "p arm" as in **Figure 1**. Chromosomes are numbered from 1 to 22 in both sexes and called autosomes, while the last one remaining take letters X and Y which are responsible for the gender. In female, X chromosome is duplicated, whereas Y chromosome is combined with X chromosome in male [24, 25] (**Figures 2** and **3**).

The nitrogenous bases are organic molecule with a nitrogen atom that bears chemical prosperities of a base and involves four letters in addition to fifth letter used in ribonucleic acid (RNA), and classified into two main compounds: pyrimidine cytosine (C), thymine (T), and uracil (U); and purine guanine (G) and adenine (A), respectively [27]. They were arranged in unique position in genes, which makes up combinations with permutations and combinations. It is worth mentioning (AT and GC) that bases pair is always found together, and there are different sequences

**2**

*Autosomes and sex chromosomes of Homo sapiens from US National Library of Medicine, National Institutes of Health, Department of Health & Human Services. June 4, 2012.*

**Figure 2.** *Chromosome structure explained long and short arms [26].*

of bases pairs in DNA coded messages [28]. These bases are part of DNA, and constitute a language when arranged together acting as a guide telling cells what need to do such as growing, division, maturity, and variety functions [29].
