**3. Polymorphism**

A brief glance across a time: the beginning of the human genetic polymorphism was belonging to the b globin gene in 1978, which utilized to recognize a heredity disease. After 2 years, in 1980, short distinctions in DNA discovered were spread over the whole human genome. It was described by utilized restriction fragment length polymorphisms (RFLPs) method. Further complicated interesting information of DNA polymorphisms was reported in 1985. They were named minisatellites. The empirical arguments about DNA fingerprinting remained to the 1990s. With the trial of OJ Simpson in the USA in 1995, the DNA proofs play a very important role in forensic medicine history presented by the prosecution; OJ Simpson was acquitted. This event call attention to the proofs of DNA has great significance [51].

When we see the great diversity of human ethnicities, really we find it shocking that all of these different ethnicities share a genetically identical sequence at 99%. The range of their variances is only within limits 0.1% of sequence genetic that differs between double chromosomal threads, **Figure 4**, [52, 53]. It is a small ratio of variances (1%) indeed, but it is accountable for the multiplicity in person's phenotypes and receptiveness of them to ecological contacts [53, 54].

Polymorphism at the DNA grade contains a broad domain of variations from single base pair alteration, numerous unite pairs, and frequent sequences [55]. One of the most famous types of genetic variations is the genetic mutation. Genetic mutation can be definite as order variants which happen in a smaller than 1% of the populace, whereas the extra prevalent variants are identified as polymorphisms. The greatest public hereditary variants than 1% are single nucleotide polymorphisms (SNPs) [53, 54].

Generally, genetic polymorphism can be available in numerous designs, comprising: single nucleotide polymorphisms (SNPs), tandem repeat polymorphisms which include a variable number of tandem repeats (VNTRs) and short tandem

**7**

**Figure 5.**

*Single nucleotide polymorphism for two alleles.*

*Genetic Polymorphisms*

variations (CNV) [55].

polymorphism (**Figure 5**).

genomic variants [57, 58].

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

**3.1 Single-nucleotide polymorphism (SNP)**

genetic factors of malady inside relatives [59–62].

**3.2 Polymorphic repetitive sequences**

repeats (STRs), insertion/deletion polymorphisms, transposable elements (TE) or Alu repeats also known as "jumping genes," structural alterations, and copy number

For the studying diverse kinds of DNA polymorphisms, different techniques can be utilized, such as restriction fragment length polymorphisms (RFLPs) accompanied by southern blots, polymerase chain reactions (PCRs), hybridization methods (southern and northern blotting) utilizing DNA microarray chips, and whole genome sequencing (WGS) [55]. The following is an illustration of the most famous

Single nucleotide polymorphisms (SNPs) (pronounced: snip) are an alteration in a lone DNA order structure building block unit: (A, T, C, or G) which termed a nucleotide, **Figure 2** [56]. It is the simplest formula of genetic difference among persons. SNPs are the most frequent occurrence from all genetic variants, which happen usually in a person's DNA. It is a ratio of occurrence near 90% of human

They may be occurring one time in each 300 nucleotides on usual, that is, average is about 10 million SNPs in the individual's genome. Greatest frequently, those SNPs are set between genes or within genes. They may perform as living signs and/or hereditary indicators, aiding experts find sequence, which are linked with disease. As soon as SNPs happen inside a gene or in an adjusting area nearby a gene, they might show an additional strong impact in disease via stirring the gene's role. However, the SNPs generally have no influence on the general state of health. Moreover, investigators have instituted that SNPs might assist and guess a person's reaction to definite medications. Additionally, they are utilized for a pathway of

The extension of the human genome threads that include gene sequences or intergenic and include retro (pseudo) genes and transposons are composed of small sequences of nitrogen bases that have repeated in tandem. It can consist of more two-thirds of human DNA. The number of units of these tandems in a specified site is extremely variable between separated persons. Tandem repeat polymorphisms include a variable number of tandem repeats (VNTRs) minisatellites and short tandem repeats (STRs) microsatellites. Both of VNTRs and STRs are the same in the total grounds. The difference between different alleles is consequence to a difference in the number of repeat bases that exist in alleles that are of various lengths, and later, tandem repeat polymorphisms have been identified as length polymorphisms. So, widely distinguished types from mini- and microsatellites

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

*The Recent Topics in Genetic Polymorphisms*

**3. Polymorphism**

significance [51].

phisms (SNPs) [53, 54].

occur in DNA sequence either by mistake during copy process or by environmental effectors. Sometimes mutations affect individuals directly or indirectly and are

A brief glance across a time: the beginning of the human genetic polymorphism

When we see the great diversity of human ethnicities, really we find it shocking that all of these different ethnicities share a genetically identical sequence at 99%. The range of their variances is only within limits 0.1% of sequence genetic that differs between double chromosomal threads, **Figure 4**, [52, 53]. It is a small ratio of variances (1%) indeed, but it is accountable for the multiplicity in person's pheno-

Polymorphism at the DNA grade contains a broad domain of variations from single base pair alteration, numerous unite pairs, and frequent sequences [55]. One of the most famous types of genetic variations is the genetic mutation. Genetic mutation can be definite as order variants which happen in a smaller than 1% of the populace, whereas the extra prevalent variants are identified as polymorphisms. The greatest public hereditary variants than 1% are single nucleotide polymor-

Generally, genetic polymorphism can be available in numerous designs, comprising: single nucleotide polymorphisms (SNPs), tandem repeat polymorphisms which include a variable number of tandem repeats (VNTRs) and short tandem

*Human genetic polymorphism is identical in sequences at 99% and variation sequences only about 1% [52].*

was belonging to the b globin gene in 1978, which utilized to recognize a heredity disease. After 2 years, in 1980, short distinctions in DNA discovered were spread over the whole human genome. It was described by utilized restriction fragment length polymorphisms (RFLPs) method. Further complicated interesting information of DNA polymorphisms was reported in 1985. They were named minisatellites. The empirical arguments about DNA fingerprinting remained to the 1990s. With the trial of OJ Simpson in the USA in 1995, the DNA proofs play a very important role in forensic medicine history presented by the prosecution; OJ Simpson was acquitted. This event call attention to the proofs of DNA has great

prone more susceptible to certain disease circumstances [50].

types and receptiveness of them to ecological contacts [53, 54].

**6**

**Figure 4.**

repeats (STRs), insertion/deletion polymorphisms, transposable elements (TE) or Alu repeats also known as "jumping genes," structural alterations, and copy number variations (CNV) [55].

For the studying diverse kinds of DNA polymorphisms, different techniques can be utilized, such as restriction fragment length polymorphisms (RFLPs) accompanied by southern blots, polymerase chain reactions (PCRs), hybridization methods (southern and northern blotting) utilizing DNA microarray chips, and whole genome sequencing (WGS) [55]. The following is an illustration of the most famous polymorphism (**Figure 5**).
