What is a Genome? Facts About the Genome

The human genome is the entire nucleic acid sequence for humans. It is encoded as DNA in the 23 chromosome pairs in the nucleus of the cell and is a small circular DNA molecule found within the mitochondria. In most cases, these are defined separately as the mitochondrial genome and nuclear genome. Attempts in Deciphering the Human Genome In February 2001, the Human Genome Project published the first draft sequence and first analysis of the human genome. Just one day after the announcement of the Human Genome Project, Celera Corporation published its genome compilation.

The Human Genome Project is the most complete assembly representing approximately 90% of the human genome in curated form. The assembly manufactured by Celera Corporation is considered less accurate due to the direct shotgun approach used. Since then, international cooperation has made great efforts to transform this first draft into a full genome sequence with high fidelity and maximum coverage.

In 2004, the sequencing of the Human Genome Project covered approximately 99% of the euchromatic genome with only 341 gaps in the sequence, with an error rate of approximately 1 event per 100,000 bases. Most of the remaining euchromatic spaces are associated with segmental copies. Recovery in the human reference genome has not stopped and to date the Genome Reference Consortium is developing it. Among all vertebrates, the human genome was the first to be sequenced with such high precision and near completion. Molecular Organization of the Human Genome Human DNA is packaged into chromosomes, which are the filamentous structures of nucleic acids and protein found in the cell nucleus, carrying genetic data in the form of genes.

Diploid organisms like humans carry two sets of genetic information; one set is inherited from father and one set from mother. The human genome consists of about 3 billion base pairs and 46 chromosomes. Human 46 chromosomes are arranged in 23 pairs, including 22 pairs of autosomal chromosomes plus 23 pairs of sex chromosomes (XY) and female (XX) of the male. Therefore, every human somatic cell has 22 pairs of autosomal chromosomes and 1 sex chromosome pair.

The 22 pairs of chromosomes are numbered in roughly descending order, with the exception of chromosomes 21 and 22, the first of which is the smallest human chromosome. These are all large linear DNA molecules found in the cell nucleus. In the smallest human chromosomes, the DNA molecule contains about 50 million nucleotide pairs, while the largest chromosomes contain about 250 million nucleotide pairs. The human genome also contains a small DNA molecule found in individual mitochondria.

The human genome is generally classified as coding and non-coding DNA sequences. While exons or coding DNA sequences made up of protein-encoding genes represent only a small percentage (<2%) of the genome, regions of DNA that do not encode (introns) in the human genome do not encode proteins that represent more than 98% of the proteins. Some parts of the non-coding DNA regions contain genes for RNA molecules with important biological functions such as ribosomal RNA (rRNA) and transfer RNA (tRNA).

ENCODE (Encyclopedia of DNA Elements), contemporary genome research, aims to explore the entire human genome using various and new experimental tools to reveal the functional role and evolutionary origin of non-coding DNA regions. Different regulatory sequences can control gene expression in the human genome. Although some studies reported that these sequences represent 8% of the genome, extrapolations from the ENCODE project found that 20-40% of the human genome may be gene regulatory sequences. Enhancers, a type of non-coding DNA found in the human genome, regulate when and where genes are expressed.

Mobile elements in the human genome can be divided into DNA transposons or retrotransposons according to their mechanism of action. DNA transposons act through a cutting and splicing mechanism in the human genome while retrotransposons move through an RNA intermediate in a retrotransposition process through a copying and splicing mechanism. Human mobile elements represent about 45% of the human genome. All elements are the most abundant transposable genetic element, with about 50,000 active copies. Almost half of the human genome consists of repetitive DNA sequences. Approximately 8% of the human genome consists of tandem repeats, which are short sequences of DNA that are repeated from head to tail with a variable trend like “CAGCAGCAG… ..”

These tandem sequences can range in length from two nucleotides to tens of nucleotides. Tandem repeats are highly variable, making them extremely valuable tools in forensic DNA analysis and genealogy DNA testing. Interesting Facts About the Genome The genome is an organism’s complete set of genetic instructions. Each genome contains all the information needed to build this organism and allow it to grow and develop. The human body consists of millions of cells (100,000,000,000,000), each with its own set of instructions, and it can be called a recipe book for the body.

This set of instructions is known as the genome and is made up of DNA. Every cell in the body, for example, a skin cell or liver cell, contains the same set of instructions:

• The instructions in the genome are made up of DNA.

• There is a unique chemical code in DNA that guides the growth, development and health of the person.

• This code is briefly determined by the order of the four nucleotide bases that make up DNA, adenine, cytosine, guanine and thymine, A, C, G and T.

• DNA has a structure that is twisted in the form of a double helix. DNA chromosomes are wrapped in structures called individual strands Chromosomes are located in every cell nucleus

• Sections of DNA within chromosomes can be read together to create genes.

• Genes control different traits such as eye color and height.

• All living things have a unique genome.

• The human genome is made of 3.2 billion bases of DNA, but other organisms have different genome sizes.

• If 3.2 billion letters of the genome are printed; A 61 m high paperback stack can be filled, telephone directories of 200 to 500 pages can be filled, if we read one letter per second for 24 hours a day, we can teach a hundred years and extend 3,000 km (1,864 miles). That means the distance from London to the Canary Islands, Washington to Guatemala, or New Delhi to Hanoi is roughly close.

A genome is the genetic material of living things. It is all the hereditary instructions for building, operating, and maintaining an organism and passing life on to the next generation. In most living things, the genome is made from a chemical called DNA. The genome contains genes that are packaged in chromosomes and affect specific characteristics of the organism. Considering these relationships as a series of tiny boxes nested within one another, the largest box represents the genome. Inside, a smaller box represents chromosomes. Inside is a box representing genes, and at the end, the smallest box is DNA. In short, the genome is split into chromosomes, chromosomes contain genes, and genes are made of DNA.

The word “genome” was coined in 1930 even if scientists did not know why the genome was made. They just knew how important the genome is to have a name. Each of the world species has its own genome; canine genome, wheat genome, cow’s genomes, cold virus, Chinese cabbage, Escherichia coli (a bacterium that lives in the human intestine and animal intestines), etc. they are all different.

So genomes belong to species, but also to individuals. Every giraffe in the African savannah has a unique genome, like every elephant, acacia tree, and ostrich. If it is not an identical twin, the genome is different from all other humans on earth, in fact, different from other humans who have lived before. Despite being unique, the genome is still a recognizable human genome. The difference is only a matter of degree: the genome differences between the two individuals are much less than the genome differences between humans and the closest living things, the chimpanzees.

Reference: https://www.genome.gov/about-genomics/fact-sheets