Knowledge of genetics or inheritance is a branch of biology that explores the inheritance and diversity of organisms. The genetic word was derived from the Greek word γενετικός – geneticos (“genitive“) in 1831. The root of this word is based on the word γένεσις – genesis (“origin“).
With the knowledge that the properties of living things are hereditary, plants and animals have been rehabilitated since prehistorictimes. However, the modern genetics of understanding the mechanisms of hereditary transmission only began in the mid-19th century with the work of Gregor Mendel. Although Mendel did not know the physical basis of heredity, she observed that these properties were transmitted in a discrete fashion; Today these genetic units are called “genes”.
Genes correspond to certain regions in DNA. DNA is a chain molecule composed of four types of nucleotides. The sequence of nucleotides on this chain is the genetic information that organisms inherit (information). In nature, DNA has a two-chain structure. Each “strand” in DNA is complementary to one nucleotide, ie each strand has the ability to be a template to form a new strand of itself. This is the physical mechanism that works for the copying and inheritance of genetic information.
The sequence of nucleotides in DNA is used by the cell to produce amino acid chains. Protein is formed from these. The order of amino acids in a protein corresponds to the order of the nucleotides on the go. This association is called genetic code. The sequence of amino acids in a protein determines how the protein will take a three-dimensional shape. This structure is responsible for the function of protein as well. Proteins perform almost all the functions needed for the life and reproduction of cells. A change in the DNA sequence changes the amino acid sequence of a protein and thus its shape and function: this can lead to important consequences in the cell and in the organism to which it is attached.
Although genetics plays an important role in determining the appearance and behavior of organisms, in the formation of the end, the organism interacts with the environment and genetically interacts. For example, although genes play a role in the length of a person’s neck, there is also a great influence on the person’s nutrition and health.
Although genetics began in the mid-1800’s with practical and theoretical studies of Gregor Mendel, other theories of inheritance existed before Mendel. One theory that was popular at the time of Mendel was the concept of mixed inheritance: it was the idea that individuals inherited a homogenous blend of the characteristics of their parents. Mendel’s work has falsified this, showing that features are the union of discrete genes, not a mix of continuous features. (For example, when red and white-eyed flies mate, they have either red or white eyes, but not pink eyes.) Another theory that was valid in that period was the inheritance of acquired traits: it was the belief that the traits possessed the characteristics that the parents strengthened. This idea (generally attributed to Jean-Baptiste Lamarck) is known to be wrong today.
People’s experiences do not change the genes they transmit to their offspring. Among other theories was the idea that Charles Darwin’s Pangenezis idea (which both suggests hereditary and acquired features) and Francis Galton’s new interpretation of Pangenezis, both inherited and inherited.
First genetic experiment, Mendel and Classical Genetics
The roots of modern genetic science are based on the observations of Gregor Johann Mendel, an Austrian (German-Czech) Augustinian monk and botanist.
Mendel, considered to be the father of this popular science of the day, has studied in detail the inheritance characteristics of plants. From 1856, Mendel began collecting the seeds of various peas (Pisum sativum) varieties and cultivating them in the monastery garden, examining the differences between them. After 10 years of observations and experiments, he published important findings of his work on a famous review called “Versuche Über Pflanzenhybriden” (“Experiments on plant hybrids“) and this article was presented to the Brunn Association of Natural History in 1865. Mendel has followed the hereditary repetition of certain features of pea plants and has shown that they can be described mathematically. Mendel’s work suggests that heredity is not acquired, it is granular, and that the inheritance of many properties can be explained by simple rules and proportions.
Given that concepts such as DNA, chromosome, meiosis, and the like have not yet been laid out and are not known at the time, it can be said that evaluating Mendel’s merely phenotypic character distinctions is extremely successful.
Given that concepts such as DNA, chromosome, meiosis, and the like have not yet been laid out and are not known at the time, it can be said that evaluating Mendel’s merely phenotypic character distinctions is extremely successful.
Until the 1890s after Mendel’s death, the importance of his work was not widely understood. Other scientists working on similar problems at that time are rediscovering their work. Sixteen years after his death, Hugo De Vries in the Netherlands, Correns in Germany, and E. Von Tschermak in Austria, demonstrated the validity of Mendel’s laws in various plant species, unaware of each other, and gathered all the results under the name “Mendel’s law” . Mendel’s work also suggested the use of statistical methods in inheritance studies.
The term “genetics” was introduced in 1905 by a prominent advocate of Mendel’s work in a letter to William Bateson sent to Adam Sedgwick. In his opening speech at the Third International Plant Hybrid Conference held in London in 1906 Bateson used the term “genetics” to describe its inheritance work, making this term popular. (As an adjective, genetics is derived from the Greek genesis – γένεσις (“source“), which is derived from genno – γεννώ (“giving birth“), Ta was used)
After Mendel’s work has been rediscovered and popular, many experiments have been done to bring the molecular basis of DNA to daylight. Thomas Hunt Morgan, who emerged from his observations on the white-eyed Drosophila (fruit sliver), suggested that genes appeared in chromosomes in 1910 and revealed the existence of mutations in 1911. Morgan’s student, Alfred Sturtevant, used the phenomenon of genetic linkage and in 1913 published the first “genetic map” of genes sequencing along the chromosome.
Although it is known that chromosomes contain genes and that they consist of protein and DNA, it is not known which one is responsible for inheritance. In 1928, Frederick Griffith explained the phenomenon of transformation he discovered in his published article. Sixteen years later, in 1944, Oswald Theodore Avery, Colin McLeod and Maclyn McCarty showed that the DNA molecule responsible for this transformation was DNA. The Hershey-Chase experiment in 1952 also proved that DNA (as opposed to protein) is the genetic material of viruses and that other molecules can not be responsible for inheritance.
James D. Watson and Francis Crick unraveled the structure of DNA in 1953 and showed that it was a helical structure of the DNA molecule using X-ray diffraction studies of Rosalind Franklin’s work. Their binary helical model showed that the nucleotide sequence was complementary to the other strand. This structure did not show that the nucleotide sequences could hide the genetic information, but at the same time showed the physical mechanism for replication: as the two strands separate, each strand could use its own sequence as a template for the formation of a new strand that would match itself.
Although this structure describes the inheritance process, It is not yet known how DNA affects cell behavior. In the following years, some scientists tried to understand the mechanism by which DNA controls the protein production processes in ribosomes, and found that the genetic code of DNA was read and solved by messenger RNA (mRNA). RNA is a molecule made up of nucleotides, similar to DNA; The nucleotide sequence of the mRNA is used to generate the amino acid sequence in the proteins. The translation of the nucleotide sequence into the amino acid sequence takes place through the genetic code.
This molecular level of inheritance has led to an understanding of the molecular structure of DNA and an exploding exploitation of new knowledge in biology. In 1977, Frederick Sanger’s chain terminated DNA sequencing method was an important development; This technology has enabled scientists to read DNA molecules. The polymerase chain reaction, developed by Kary Mullis in 1983, allowed DNA isolation and the desired regions of DNA fragments to be readily amplified. This and other techniques, as well as the team work of the Human Genome Project on the one hand, and the special work of Celera Genomics on the other hand, in 2003, the human genome sequences were completely sun-exposed.
Intermittent inheritance and Mendel laws
At the most basic level, the heredity in organisms comes to life through the discrete properties we name today. The first person to observe in this regard was Gregor Mendel, a pea plant who also worked on the separation of hereditary properties. (The size of a feature is two or more, if it is clustered around several values. In his research on flower color, Mendel observed that each flower was either purple or white, not an intermediate color. The different, interdigitated versions of the same gene are called alleles.
Mendel gathered seeds from each of the different plant varieties and came out in her garden. Mendel, who subjected the pea plants to regular “pollination“, discovered that 7 of these properties did not change, and observed how these 7 properties in peas (the shape of the beads, the color, the size of the plants, etc.) The individuals he has obtained at each turn are separated according to whether they resemble each other and their parents. So I obtained 7 pure progeny with different characteristics. In crossings with them, he found that certain features did not change. Each of these properties gave the name “pure property“. When the two peers cross the “pure property“, only this pure property emerges, which constitutes the basis of Mendel’s laws.
Mendel also observed that some traits were dominant in the crossings he had made. For example, long characters dominated the character of brevity, and hybrid individuals were long-looking. As a result of crossing of two long hybrids, 25% pure long, 25% pure short, 50% hybrid long.
Mendel observed that in the trial run on the color of the flowers of the pea plant, the color was either purple or white and never a mixture of these two colors appeared. These different versions of the same gene are called alleles.
In pea plants, every organism has two alines per gene. Many organisms, including humans, have this inheritance pattern. (In genetics, it is assumed that one of the two alleles of a genus in such an organ is passed from the mother to the other.) The organisms with two copies of the same allele are called homozygotes and the organisms with two different alleys are called heterozygotes.
The genetic makeup of an organism is called a genotype. Observable features that the organism has are called the phenotype.
Heterozygous organisms generally determine the phenotype of the organism so that the qualities of one of the alleles will suppress the other; The other alleys that are observed to be “dominant” in predominance of the phenotype of the organism’s qualities and dominant in their qualities not in the phenotype are called “recessive” (recessive). However, sometimes an allele seems not to be dominant in the full sense, which is called “incomplete dominance”. Sometimes it is observed that both characteristics of both alleles are more effective, which is called “coercion” (codominans).
When a pair of organisms is mated, the offspring take one of two alleles from the mother and the other from the father in a random fashion. All these observations made on the discrete inheritance and the separation of the alleys are collectively known as Mendel’s first law or the Law of Deconstruction.
Symbolic display system and diagrams
Geneticists use schemas and symbols in their heritages. A gene is represented by one or several letters. In this case, the capital letter represents the dominant letter, the lowercase letter is the recessive letter. Usually a “+” symbol is used to represent a normal, non-mutant allele for a gene. In fertilization and production experiments with Mendel, the parent is referred to by the initial letter “P”, the offspring of the word “parent”, with the offspring F1 (“F” is the first letter of the word “filial”, meaning “first generation”). F2 is referred to as a new generation of offspring F2, which occurs when F1 generations mate with each other. One of the common schemes used for predicting the result of crossing is known as “Punnett square”.
When geneticists examine human genetic diseases, they often use a genealogy chart to represent the inheritance of features.
Interaction of genes
Organisms contain thousands of genes, and coexistence of these genes in organisms that reproduce with sexual intercourse is often independent of each other. That is, for example, the inheritance of a yellow or green colored pea allele is not related to the inheritance of alleles that determine the white or purple appearance of the flowers. This phenomenon, known as the “second law of Mendelian” or “the Law of Independent Discipline“, means that the alleles of the different genes involved in coming from both parents can come together in many different combinations while forming their own sperm. (However, some genes that show “genetic linkage” do not come together independently, this issue will be covered in more detail below.)
As is often seen, different genes can interfere with each other in a way that ensures the same phenotype. The genes of the European-origin Omphalodes verna plant are examples of this. In this plant there are two allelic genes that allow the flowers to be blue or magenta. But there is another gene in the plant that controls whether the flowers will be colored, that is, it will be colored or white. When the plant has two copies of the white allele of the plant, the flowers become white, without causing one of the blue and magenta colorants on the first branch to be effective in the plant. This interaction between the genes is called “epistasis” and, as an adjective, the first gene is said to be “episatic” on the second.
Many features are permanent (rather than human or skin color) rather than a discrete feature (as in the case of white or purple flowers). These complex features are the products of many generations. The effect of these genes is balanced at various levels by the influence of the environment in which the organism is experiencing. The degree to which an organism’s genes contribute to such a complex feature is called “heritability”. The extent of inheritance of a property is relative to the changing effects of the environment on that property. For example, the heritability of a person’s inherited heritability is 89% in U.S.A., whereas in Nigeria, where nutritional and health problems are present, the impact is much greater.
Heredity is molecular-based
DNA and chromosomes
Genes are molecular-based deoxyribonucleic acid (DNA). DNA consists of four types of nucleotides: adenine (A), cytosine (C), guanine (G), and thymine (T). Genetic information (inheritance information) exists in the sequence of nucleotides, and genes are present as sequences extending along the DNA chain. The only exceptions to this rule are viruses; Viruses sometimes use RNA molecules that are similar to DNA; Because the genetic material of viruses is RNA.
DNA is normally a two-stranded molecule filled in a double helix. Each nucleotide in one of the two strands of DNA forms a pair with the nucleotide partner in the opposite strand; That is, A forms a pair with T, with C in G. Thus, each of the two strands has all the necessary information, and the other strand contains the redundancy of this information. This structure of DNA is the physical basis of heredity. In DNA duplication, the genetic information is copied by decomposing the strands and using each strand as a template for the new strand pair.
Genes are arranged in a linear array along DNA sequence chains called chromosomes. In bacteria, each cell has a simple circular chromosome, while eukaryotic organisms, including plants and animals, have DNAs arranged in multiple linear chromosomes. These DNA chains are extremely elongated; For example, the longest human chromosome is 247 million base pairs long.
DNA in a chromosome, along with structural proteins that regulate, constrict, and control access to it, form a structure called chromatin. In eukaryotes, chromatin is usually composed of nucleosomes, which are structures made up of histone proteins, which are regularly spaced on DNA and wrapped around DNA. The whole of the hereditary material in an organism (ie, in general, all of the DNA sequences in all chromosomes) is called the genome.
Although diploid organisms have only one copy of each chromosome, in diploids where most of the animals and many plants are involved, there are two copies of each chromosome, and thus two copies each. Two genus of two genus, sister chromosomes, are located in the same “locus” (positions); Each of these children was taken from one parent (one mother, one father).
An exception to this is in sex chromosomes that play a role in determining the sex of the organism. The Y chromosome, which has few genes in humans and mammals, initiates the development of masculinity, but the other, X chromosome, resembles other chromosomes, including a few genes not related to sex determination, from these chromosomes (eg, 23rd chromosome in the human). While the teeth have two copies of the X chromosome, the men have an X and a Y chromosome. Hence, examples of unusual inheritance that occur as sex-related diseases also come from this numerical difference in the copy of the X chromosome.
When cells divide, their entire genome is copied, and every cubicle inherits (inherits) a copy of it. This process, called mitosis, is the simplest form of reproduction and the basis of “asexual reproduction”. Asexual reproduction may also occur in some multicellular organisms, such as providing a puppy inheriting the genome of a mother or father. Genetically, the offspring of parents are called clones.
In eukaryotic organisms it is usually “sexual reproduction”. In sexual reproduction, a progeny is produced that contains a mix of hereditary material from both parents. In the sexual reproduction process, there is an alternating order between haploid and diploid cell types. Haploid cells fuse together to combine genetic material and create a diploid cell with double chromosomes. Diploid organisms divide without DNA cloning, bringing haploid cells to the field. In this way, the haploid cells from the juvenile have inherited one or both of each pair of chromosomes randomly. Most of the animals and plants spend almost all of their lives as diploid, haploid forms are only single-celled gametes.
Although the bacterial breeder uses this haploid / diploid method, they use many methods to acquire new hereditary information. For example, some bacteria transfer a circular DNA fragment from one gene to another in a way called conjugation. Bacteria can also take DNA fragments in their environment and incorporate them into their genomes, which is known as transformation. As a result of these processes, the transfer of genetic information pieces between mutually unrelated organisms called “horizontal gene transfer” occurs.
Chromosomal fragment replacement and genetic linkage
The diploid ministry of chromosomes allows “independent separation” of genes in different chromosomes, in the course of sexual reproduction, to form new gene combinations. In these assemblies (recombination), genes would never merge theoretically in the same chromosome, unless there was a so-called crossover process in which the chromosomes changed parts. During this process, chromosomes exchange DNA fragments, allowing the gene alleles to change. This process of chromosomal fragmentation usually occurs during meiosis, during a series of cell divisions that cause gamete haploid “germ cells”. (These germ cells then combine to bring the organism to the fountain.)
The probability of recombination between two specific points on the chromosome depends on the distance between these two points. Since the genes that are far enough are always recombined, alleles of these genes are randomly distributed. In the case of relatively close genes, the low likelihood of being a crossover means that these genes are not genetically linked; Both genes tend to inherit alleles together. The amount of linkage between the sequences of the genes constitutes a linear linkage map, which roughly corresponds to the arrangement of the genes along the chromosome.
Genes express their functional effects, usually by the production of proteins, which are responsible for many of the functions in the cell. Proteins are amino acid chains, and a gene’s DNA sequence (via an RNA) is used to generate a unique sequence of a protein. This process, called software (transcription), begins with the production of an RNA molecule that has a sequence that comes from scratching the genome DNA sequence. This messenger RNA molecule is then used in a process called translation to generate an amino acid sequence corresponding to the information in the RNA sequence. Each three nucleotide group in the RNA sequence is termed a codon, each of which corresponds to one of the 20 amino acids that make up the proteins. This association between the RNA sequence and the amino acids is called the genetic code. This information flow is unidirectional; Ie information is transferred from the nucleotide sequences to the amino acid sequence of the proteins, not from the protein to the DNA sequence. This phenomenon is called “the central dogma of molecular biology” by Francis Crick.
A protein amino acid sequence forms the three-dimensional structure of that protein, which is closely related to the protein’s function. Some of these are simple structured molecules, such as fibers formed in collagen protein. Proteins called enzymes can bind to other proteins and simple molecules, acting as catalysts, facilitating chemical reactions in the molecules to which they are attached (without altering the protein’s own structure). The structure of the protein is dynamic; For example, the hemoglobin protein has different forms, bent and bent while facilitating the uptake, transport and release of oxygen molecules in mammalian blood.
Even the difference of a single nucleotide in DNA can cause a change in the amino acid sequence of a protein. Since the structures of proteins are the result of their amino acid sequences, such a change can change the properties of that protein; For example, to alter the properties of the protein, the destabilization of that protein’s structure, or changes in its interaction with other proteins and molecules. Sickle cell anemia, a hereditary disease in humans, is an example of this. This disease is caused by a single base difference in the coding region that determines the β-globin fraction of hemoglobin; This difference in a base causes an amino acid change that causes the physical properties of the hemoglobin to change. The resulting “sickle cell” versions of hemoglobin, which result from changing physical properties, cling to each other, stack up and form fibers. These fibers cause the degradation of the red blood cells that transport the protein. Sickle-shaped cells do not flow easily in the blood vessels, they tend to break up or block blood vessels. These problems eventually lead to medical conditions related to this disease in the person.
Some genes are transcribed into RNA and not translated into proteins, which are called “non-coding RNA” molecules. These products, in some cases, play a role in critical cellular functions (such as ribosomal RNA, carrier RNA). RNA may also have a regulatory effect role via “hybridization” interactions with other RNA molecules. (E. G., MicroRNA)
From Birthdays – later winners
Genes, while containing all the information about the functioning of an organism, play an important role in determining the environment, the final phenotype. The genetic factor and environmental factor dilemma are expressed in the English phrase “nature versus nurture” (nature vs. nurture), which is used to mean “congeners and later acquire”. The phenotype of an organism depends on its interaction with heredity. An example of this is the case of “heat sensitive mutations”. Generally, an amino acid that changes within a protein sequence does not alter its behavior and its interaction with other molecules; But it destroys the stability of the work. Because molecules move faster and collide with each other at high temperatures, such an amino acid change leads to impairments that manifest as protein structure deterioration (degradation) and impaired functioning. In low temperature environments, the protein structure remains stable and the process continues normally. This type of mutation manifests itself visibly in color on the fur of Siamese cattle: the mutation in an enzyme responsible for pigment production leads to deterioration and impairment of structural stability in the high temperature regions in the deep, while in colder regions such as the legs, ears and tail, the protein continues its functioning without weakening; So that the cat has a dark fur on the extremities.
While the genome of an organism contains thousands of genes, all of these genes need not be active at all. A gene is & quot; expressed & quot; when the transcription of the mRNA occurs (and when the protein is translated). There are many cell methods that control the expression of genes. For example, proteins are produced only when the cell needs it. Transcription factors are proteins that either regulate or inhibit transcription of the gene. For example, in the genome of the Escherichia coli bacterium there is a series of genes necessary for the synthesis of the tryptophan amino acid; But after the tryptophan is ready for use in the cell, these genes are no longer needed. The presence of tryptophan directly affects the activity of genes; Tryptophan molecules are linked to a “tryptophan repressor” (a transcription factor), which changes the structure of the repressors so that the repressors are linked to the genes. The tryptophan repressor stops the transcription and expression of the genes, and thus provides the negative feedback regulation of the tryptophan synthesis process.
Differences in gene expression are particularly evident in multicellular organisms, where, in such organisms, cells all have the same genome, but have very different structures and behaviors resulting from the expression of different gene clusters. All the cells in a multicellular organism breed from a single cell. This single cell reacts to external and intercellular signals during the process of differentiating into different cell types, gradually forming different types of gene expression, forming different types of behavior. There is no single gene responsible for the development of structures in multicellular organisms; These different types of behavior arise from the complex interactions between many cells.
During the DNA duplication process, random errors occur in the polymerization of the second strand. These errors, called mutations or alterations, can have a strong effect on the phenotype of the organism, especially if they occur in a genetic protein coding sequence. But the DNA polymerase enzyme’s ability to correct errors makes the rate of these errors extremely low; The error rate was observed to be 1 error per 10-100 million cases. Processes that increase the rate of change in DNA are said to be mutagenic. Mutagenic chemicals often interfere with base pairing, leading to errors in DNA replication. Ultraviolet radiation causes mutations by damaging the DNA structure. Although the chemical damage in DNA comes naturally, the cells use “DNA repair” mechanisms to repair mismatches and distortions. However, repairs can sometimes not restore DNA back to its original state.
Alignment during meiosis division (mutually adjacent sequences on two chromosomes) can also cause mutations in organisms that exchange chromosomal parts with the crossover and recombine genes. These errors are particularly likely to be caused by misalignment of partner chromosomes, caused by similar sequences; Which makes some regions of the genome more prone to mutation. These errors create major structural changes in the DNA sequence; Duplications, inversions (deletions), deletions (deletions), or accidental transfer of parts between different chromosomes (translocation) may occur in large regions of the chromosome.
There are about 25,000 genes in human DNA, and over 6,000 genetic diseases have been detected in these mutations resulting in genetic disorders, and treatment is sought. It is known that mutations lead to cancer, especially mental retardation, premature aging and thousands more diseases.
Natural selection and evolution
Mutations result in the appearance of different genotypic organisms, and these differences result in the formation of different phenotypes. Many mutation organisms have little effect on the phenotype, health and reproduction (natural selection) fitness. Mutations that are the effect are often harmful, but sometimes there are also mutations that can be useful in the context of the environmental conditions the organism is in.
Population is a genetic subtype that investigates the sources, distributions, and how these distributions change over time in these genetic populations. The frequency of an allele in a population can be affected by natural selection; The high rate of survival and survival of individuals carrying a particular locus can cause that allele to become more frequent in that population over time. At the same time, there may be changes in the frequency of alleles, also known as “genetic drift,” under the influence of the chance factor, that is, in the random flow of events. Genetic drift is defined as a change in the gene pool of a population, unlike natural selection, that occurs entirely by chance, rather than by directing the selection of appropriate genes.
The genomes of organisms can change over many generations, resulting in a phenomenon called evolution. As a result of the selection for mutations and mutations beneficial, a living thing can evolve into a more harmonious form of environment. This process is called adaptation. New species are formed by a process known as speciation. Speciation usually arises from genetic differentiation, which is caused by geographically separate falls of different populations.
Since the DNA sequences are moving away from each other during evolution, these differences between the sequences can be used as a “molecular clock” to calculate the evolutionary distance between them. Genetic comparisons are generally considered to be the most accurate method of characterizing evolutionary associations among species, and this method also corrects some misleading evaluations obtained with phenotypic comparisons. Evolutionary distances between species are represented by schemes called “evolutionary tree” or “phylogenetic tree“, in which they show descent of species from a common origin and separation of species from one another over time. However, these tree schemes can not show horizontal gene transfer events between species.
Research and technology
Although genetics originally worked on a broad genome of organisms, the researchers began to privatize a subset of organisms. The fact that a significant amount of research has been done on a particular organism has also encouraged new researchers to deeper into the same organism. Thus, several model organisms have provided the basis for a substantial part of current genetic research. Model organisms are the main research topics in genetics, gene regulation, developmental genes for morphogenesis and cancer.
Model organisms have been chosen because they are partly practical; Short production times, and ease of genetic manipulation have led some of the organisms to become popular in genetic research. Commonly used model organisms include the intestinal bacterial Escherichia coli, the Arabidopsis thaliana plant from the turpentine family, Saccharomyces cerevisiae from the yeast species, Caenorhabditis elegans from the filamentous fungus, the Drosophila melanogaster and the house faeces Mus musculus.
Different research areas
In addition to the developments in genetic science, the fact that researches are becoming increasingly specialized in different fields has led to the subordination of this science branch. Some of the subgenuses of Genetics are:
Genetics (Génétique évolutive du développement) Starting from the fertilized single-celled egg stage, it examines all the molecular factors that cause the organism to form, and therefore the genes that encode them. It deals heavily with mechanisms that allow passage from a simple biological system (unicellular, radial symmetry) to a complex organism (organisms that are multiform, usually metamerized, and specialized organs), particularly by regulating bilateral symmetry. It uses model organism types (Drosophila, roundworms, zebrafish, chicken, etc.) to study the organism’s mechanisms of formation. This branch, known as the evolutionary developmental gene in French, is known as the evolutionary developmental biology in English.
Genomics: It examines the structure, composition and evolution of the human genome (three billion base pairs made up of chromosomes, the DNA whole), and contains units (genes, untranslated transcription units, microRNAs, regulatory units, promoters with transcription factors, CNG Alpha and beta channels etc.).
Quantitative genetics: Genetic components examine the variation (quantification, diversity) and heritabilities of quantitative traits (height, hair color, growth rate, etc.).
Evolutionary genetics: examines the traces of natural selection in the genomes of species and attempts to identify genes that play a key role in the survival and adaptation of species to changing environments.
Population genetics: Analyzes the strengths (and their effects or consequences) affecting the diversity of populations and species by developing mathematical and statistical methods. In other words, it is a genetic subtype that investigates the sources of the similarities and differences of the individuals in the populations. It studies on four main topics: natural selection, gene pool, mutations and gene continuity.
Molecular genetics: It is a genetic subtype that melts the structures and functions of genes, which are the genetic material of living things, at the molecular level. Molecular genetics works by using methods of molecular biology and genetics.
Ecological genetics: Genetic studies are a genetic subtype that persists in the ecological environment. Ecological genetics searches populations of living things closely related to “population genetics“.
Medical genetic researches
Medical genetics is investigating genetic diversity, human health and diseases. When an unknown gene that may cause a disease is searched, researchers often use the “genetic linkage” and genetic pedigree chart to determine the genomic location of the disease. In research at population level, researchers use the “Mendelian randomization” method to detect the location of genes in disease in the genome; This technique is particularly useful for several gene (very broad) properties that can not be precisely determined by a single gene. When any gene that is susceptible to the disease is detected as a candidate, further research is now usually made on the gene (orthologous gene) that is stable in a model organism. In addition to hereditary disease studies, genotyping techniques have also led to the development of the pharmacogenetic field, which explores how the genotype affects the response.
Although cancer is not an inherited disease, it is now considered a genetic disease. The development process of cancer in the body is formed by the combination of various events. Sometimes mutations occur when the cells in the body are divided.
E. coli is frequently used in recombinant DNA technology.
Nowadays, DNA can be changed in the laboratory in many ways as desired. Restriction enzymes used in laboratory studies are used to produce desired fragments by cutting DNA in specific sequences. The ligation enzymes allow the recombination of these fragments to be linked together, thus allowing researchers to create “recombinant DNA” by combining DNA fragments from different sources (biological species). Recombinant DNA, which is often used in studies related to “genetically engineered organisms” (GMO in English abbreviation), is in particular used in the context of plasmids (circular DNA fragments with a few genes on them). By introducing plasmids into bacteria and growing these bacteria on “agar” plates (to isolate clones of bacterial cells), researchers can replicate the added DNA fragments clonally, a process known as molecular cloning. (Cloning is also used to create clonal organisms using various techniques.)
DNA can also be amplified using a process called polymerase chain reaction (PCR). Using specific short DNA sequences, PCR can isolate a targeted region of DNA and grow it to an extreme extent. Because PCR can extensively reproduce extremely small fragments of DNA, PCR is often used to detect the presence of specific DNA sequences.
DNA sequencing and genomics
DNA sequencing, one of the most basic technologies developed in genetic studies, allows researchers to identify the nucleotide sequence in DNA fragments. A DNA sequencing method (chain termination sequence) developed in 1977 by Frederick Sanger and his colleagues is now used as a routine method of sequencing DNA fragments. Thanks to this technology, researchers have been able to investigate molecular sequences related to many human diseases.
As DNA sequencing becomes cheaper and with the help of computers, researchers have sequenced the genome of many organisms. To do this, the sequenced DNA fragments are sequenced by overlapping the regions where the sequences are the same, and the sequences of larger regions are determined (genome construction process). These technologies have also been used for the human genome, and the sequencing project for the human genome was completed in 2003. New high-volume sequencing technologies rapidly reduce the cost of DNA sequencing, with most researchers expecting the cost of sequencing a human genome to drop to a thousand dollars in the near future.
The genomic research field, which uses computational tools and analysis examples in the genomes of organisms as a result of the increase in the amount of useful sequences obtained as a result of the determinations by DNA sequencing methods, has produced. Genomics can also be regarded as a subfield of bioinformatics scientific discipline.
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