Introduction to Genetics

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Genetics. A piece of DNA: a flat-shaped portion of a spiral DNA sequence that contains blue (and white and a Little red), a nucleotide base pair that carries genetic information. The two sides of the chain are mainly reddish orange, the phosphoric acid part of the nucleotide.

Genetics is a study of genes-related disciplines, and its purpose is to try to explain what genes are and how they work. The role of genes can be thought of as the traits inherited by existing organisms from their ancestor, such as genes that often cause children to look like their parents. One of the ways in which genomics explores is to determine which traits can be inherited, and how these traits are passed down through generations.

In genetics, the characteristics of a creature are often called traits. Our most understandable traits, I'm afraid, should be biological signs--such as the color of the human eye, the height, the weight, and so on. However, there are many other types of traits, including growth and reproduction, psychological characteristics, social behavior, and disease resistance. These traits are usually hereditary, as the Chinese saying goes, "man sows, reap." But there are some traits that may vary from one environment to the other, for example, a tall son may grow smaller due to malnutrition in the growing season, although he may actually have inherited a very high gene. Under the common influence of genes and environment, it is very complicated to say how to understand the traits of individual individuals. For example, the likelihood of a person having cancer or heart disease, in addition to looking at his family history, depends on the quality of his life. This explains why some people who do not smoke can get lung cancer, while others smoke for a lifetime and live long.

The genetic information is mainly carried by a very long molecular chain, which is called DNA. The last generation of organisms can transmit their traits to the next generation by replicating this strand of DNA. We can interpret DNA as all the programs installed in a computer, and mobs are a very special kind of computer that can grow and operate according to this program. And the gene refers to one of the DNA has a functional fragment, like a program. If we know QQ or MSN is used to communicate with other people through the Internet, then TRPV1 this gene is used to make people feel spicy feeling parts.

It is important to note that the actual content may not be the same as what we call a specific gene. For example, a gene is used to describe the color of the hair, or, when the hair grows, the gene produces a variety of pigments and attaches to the hair. For Han people, their genes usually produce black hair. But the content of individual genes is different from most people, and their hair turns white. The contents of a gene are made up of hundreds or even hundreds of thousands of of things called base pairs. Some of these base pairs may mutate, which leads to differences in the content of the same gene between organisms. This mutation is usually a random event, a mutation that produces new traits, or even an important link that leads to biological evolution.

Directory[Hide]

• hereditary in 1 organisms
  • 1.1 gene and heredity
  • 1.2 Hereditary disease
• how the 2 genes work
  • 2.1 protein synthesis
  • replication of the 2.2 gene
• 3 Genetics and Evolution
• 4 Genetic Engineering
• 5 Genetics Glossary
• 6 References
• 7 Further reading
• 8 External Links

heredity in Biology [edit ] genes and Genetics [edit ]

Genes are the basic unit of complete genetic information, and parents inherit their traits by replicating and distributing the genes to the next generation. This process can be understood as a new deck of cards from the two deck cards. This new poker must be similar to the parents ', but not exactly the same. Most animals, including humans, have two sets of genes. At the time of reproduction, the parents contributed one of them to assemble two new genes. As a result, the number of genes between offspring and parents is exactly the same, except that each pair of genes in the two sets of genes are derived from their parents respectively. ^[1]

Different genes, after mixing the effect is not the same. The color of the iris of the eye, this is determined by the genes that control the color of the iris. Because there are two sets of these genes, this pair of genes we call allele. If the father's two sets of genes are green, and the mother's two sets of genes are brown, then the child of this pair of alleles must be a brown a green. When the instructions for the two genes are different, the final result will be to see how the two genes work together. In the above example, the child's eyes will be brown, because the gene's implementation of the Brown eye will mask the results of the green-eyed gene ^{[2]. We call the covered gene a recessive gene, and the same gene that covers the recessive gene is the dominant gene.}

Green eyes are a recessive trait.

Although the gene for a brown-eyed child does contain the green-eyed gene, none of the eyes are green. This surface can see the traits (called phenotype) and the actual biological genotype is not the same, this time we will use the uppercase B to denote the allele of the brown eye gene, and lowercase g to denote the green eye gene. So, the phenotype of the child is brown, and the genotype is BG, or a B allele, a G allele.

If the child grows up and is combined with another heterosexual with the same BG genotype, there are 4 scenarios for their offspring: parent B, parent B, parent G Mother B, parent G-G. However, the gene expression does not differ from the father or the mother, so the probability of BB and GG is 1/4, while the BG type is half the probability. [2] Now we can see that some of the grandchildren may have the same green eyes as his grandfather, even though his parents ' eyes are brown ^{. This phenomenon is called generational inheritance.}

In fact, the genetic condition of many traits is not as simple as the above, because sometimes a shape is a result of multiple genes working together. For example, the height of people, although the high-growing people naturally have a set of genes that can make people taller, but we are very difficult to like brown eyes or green eyes, according to the height to divide two kinds of people. Since there is more than one gene for height, each of these genes will have a certain contribution, and the final result is that height is not only one or two fixed values, but a large variation range ^{[3]. Moreover, some traits and environmental factors are also related. [4] If a person is malnourished during childhood, the color of his eye will not change, but it may not be high .}

hereditary diseases [edit ]

Many of the diseases we know, such as infectious diseases, are mainly caused by environmental factors. However, there are some diseases that can be inherited and usually appear throughout the family. There are also some so-called disorders, it is in the combination of genes and the environment, will be presented. ^[5]

Because of the hereditary disease caused by a single allele, we call it hereditary disease. Diseases such as Huntington, cystic fibrosis, and Duchenne muscular dystrophy are hereditary diseases. In the case of cystic fibrosis, the disease is caused by mutations in a single gene called "CFTR". [6] The disease is implicitly inherited, or the mutation is a recessive gene ^{. Other genetic-related diseases are associated with multiple genes, so genetic mutations from parents can only change the probability or risk of their illness. The genetic relationships of these diseases are often complex, and may even be very much related to environmental factors.}

For example, breast cancer, members of high-risk families are 50 times times more likely to get breast cancer than members of low-risk families. The big difference is probably due to the large number of alleles associated with this, and each one only has a little effect on the probability of risk ^{[7]. Scientists have now identified a number of genes associated with this, such as "BRCA1" and "BRCA2", but many have not been identified. [8] Although genetic problems are part of the cause of certain diseases, many times people tend to overlook other factors, such as alcoholism, smoking, or not exercising, which can significantly increase the risk of illness . For this reason, diseases such as breast cancer, which are genetically and environmentally determined, are difficult to predict easily based on the genetic condition of a person.}

how genes work [edit ] synthetic proteins [edit ]

An important function of genes is to allow organisms to synthesize something called protein [1] based on the information they carry, ^{and protein is an important part of the organism. For most organisms (except for viruses), cells are the smallest independent units of organisms. In humans, for example, an adult has about 100 billion cells. In contrast, some bacteria are made up of a single cell. Cells, like an ultra-small but extremely complex factory, can make any part of itself that it needs, or even replicate a new plant (called cell division). We can do a simple division of the substance in the cells: the genes emit instructions, and the proteins execute the instructions--including repairing damage on the cells, and even copying a new cell [9]. Cells produce a very rich variety of proteins, and each protein usually only accomplishes a certain kind of work. Therefore, if cells need to complete new tasks, they need to make new proteins. Similarly, if the cells need to adjust the speed of operation, they need to adjust the yield of the corresponding protein. The genes determine when the cells will produce what protein, and how much it yields.}

Gene expression requires the first transcription of genetic information from DNA to messenger RNA, which is then translated into proteins by trans-shipment RNA

Proteins are usually composed of 20 molecules, called standard amino acids, that are assembled into a chain molecule, usually spherical, like a scattered ball of yarn. The shape is determined by the amino acid sequence that makes up the protein, and the shape determines the role of the protein ^{[9]. For example, some of the surface of certain proteins, and the surface structure of another molecule to match, so the two can be closely combined. Other proteins called enzymes, like a miniature robot, modify specific molecules [10]. For example, a molecule in a particular part of the access to another molecule, or in a specific way to break up a certain molecule.}

As we further amplify the DNA sequence, we will find that it is actually repeated by a number of basic units ^{[11]. These basic units are four specific types of DNA-adenine (A), guanine (G), cytosine (C), and Thymic pyrimidine (T). When we use these abbreviations to describe a sequence of DNA, we call it a genetic code. When a cell interprets and executes these passwords, it first needs to transcribe the DNA onto the messenger RNA. Messenger RNA actually refers to the RNA that is specifically used to complete the work, and the structure of the RNA is very similar to the DNA-its basic unit is RNA (without deoxidation), and the cytosine is replaced with fluorouracil. This transcription process is controlled by other DNA sequences (such as DNA promoters), which allow the cell to know where a gene is in the DNA sequence, and to control the frequency and intensity at which the cell replicates and executes the gene. The transcription of the messenger RNA sequence is sent to the cell within a structure called ribosomes. In this structure, messenger RNA binds to transport RNA, while trans-RNA carries different amino acids depending on its sequence. With the help of ribosomes, these amino acids will eventually follow the sequence of the messenger RNA into a complete protein molecule chain. Proteins leaving the ribosome, depending on the amino acid sequence, fold themselves into different biologically active shapes. This translates the information in the DNA into the corresponding amino acid process, which is called translation [12].}

DNA replication: DNA is untied into two strands, then paired with matched DNA to form two new strands of DNA

If the nucleotide sequence in the gene changes, the amino acid sequence in the protein produced by the gene will change as well. For example, if a segment of a gene is cut off, the resulting protein will be shorter and may not function again ^{[9]. So, different alleles have different effects on living things. In the case of hair color, the color of the hair depends on the amount of melanin produced. If a person has a complete and normal set of genes used to produce black, then he will produce enough melanin to darken his hair. However, if the corresponding sequence of alleles is not the same as normal, then it may not produce melanin, the hair will become white. This condition is albinism, the person suffering from this hereditary disease not only the hair is white, even the skin is pale, even the pupil color will appear to be different from ordinary people [13].}

gene replication [edit ]

Every time a cell divides into two cells, the gene replicates to two copies. This process of replicating DNA is called DNA replication ^[11].

The DNA replication process is simple, but also very accurate, which is determined by the structure of the DNA itself. Each piece of DNA is actually made up of two chains, just like a zipper. In peacetime, DNA is like a zipper that pulls up. While copying, this zipper is solved by a specific zipper into two parts. As you can imagine, if you have two new zipper parts, you can combine them with these two old ones and form a new two zippers.

One important condition for this process is that the two halves of the zipper can be precisely matched. The two strands of DNA are made by combining their nucleotides with one another. We mentioned that there are 4 nucleotides that make up DNA, and these four nucleoside are actually 22 matched--a and T, G, and C, which means that a is not possible to match G or c. This exact matching of a pair of nucleoside, is called base pair ^[11].

So, according to one strand of DNA, the other half is exactly the same: at the time of copying, the DNA resolver divides the DNA like a zipper into two parts, and then the two strands that are unpacked are combined with the right nucleoside with the help of various enzymes to form a new two DNA. However, there are occasional minor errors in this process, such as stuffing the wrong nucleotides, which can cause changes in the DNA sequence. This is also one of the gene mutation forms ^{[14]. Mutations in genes can be produced in previously completely different proteins. Most of the time, this means a malfunction of a function, such as the presence of an albino in front of it, which normally does not produce melanin normally. However, in the occasional case, these new proteins can play a meaningful new role, or perform the same tasks as before with greater efficiency. [15] The process of altering biological traits due to changes in the DNA sequence is called Evolution .}

Genetics and Evolution [edit ] Two mice with different hair colors

[15] If a particular trait of a community becomes universal or rare, we call this process evolutionary ^{. For example, all mice on a small island can be thought of as an independent mouse community. If, after a few generations, the rare white mice became commonplace, it could be said that the color of the mouse's fur has evolved. In the genetic terminology, this is called allele frequency changes, specifically in this example, called colour allele frequency increased.}

[16] Some allele becomes common or rare, possibly due to an accidental process known as genetic drift, or by natural selection ^{. The so-called natural choice means that if a allele is beneficial to the survival and reproduction of a creature, it becomes more common after a certain period of time, and if it is harmful, it becomes rare. or the small island community, for example, if the island becomes colder and more often covered by snow due to climatic reasons, the white coat color is obviously beneficial to avoid being discovered by natural enemies, so microscope is more likely to survive and reproduce. As a result, the offspring of white-coat-colored genes become common, and dark mice become rare.}

Genetic mutations are crucial to evolution because mutations create new alleles. [17] These new alleles produce new DNA sequences and can create new proteins that do not function as before ^{. So even if there were only black mice on the island, they could eventually produce white mice because of a genetic mutation. Random mutations, and subsequent use of natural selection to leave a useful gene, so that organisms can adapt to the surrounding environment changes, and continue to multiply.}

Genetic engineering [edit ] Main article: Genetic engineering

A biological trait is a gene that is determined in a cell, that is, if we insert a new fragment into the DNA of the cell, the cell may show new traits. Genetic engineering is the use of this principle to achieve a specific purpose. For example, if food crops are injected with the genes of Arctic fish, they can produce a antifreeze protein to protect their leaves ^{[18], thus avoiding the damage caused by frost. Other examples include the ability to add genes found in Bacillus thuringiensis to produce natural pesticides. [19] The plants that add this gene can kill insects that eat these plants, but are harmless to humans . The genetically engineered plant is injected before it grows, so the gene is present in various parts of the plant, including plant seeds, pollen, and so on, so that its offspring carry these genes. This problem, which is likely to spread new genes (and the corresponding new traits) to wild plants, has gradually aroused concern. [+]}

The techniques used in genetic engineering are now being developed as a new technology for the treatment of genetic diseases, known as gene therapy. ^{[21] gene therapy works by trying to replace the part of the disease with a normal allele, which is introduced after adulthood, and therefore not all cells (especially germ cells) are genetically modified so that their children may still carry problematic genes.}

Glossary of Genetics [edit ]

Dna

A chain-like molecule shaped like a spiral long ladder consisting of 4 basic units that are repeated repeatedly. These basic units are like letters in English, and DNA is like an article written in English letters. In other words, the DNA of these basic units carries the genetic information.

Nucleotide

They are the cross-section of the foot in the middle of the DNA ladder, the repeating part of the DNA. There are four different types of nucleotides (a, T, G and C), and it is these different forms that carry the genetic information.

Chromosome

In a cell, a long sequence of DNA sequences is wound and compressed in a closed structure in a small space. The number and size of chromosomes vary from animal to plant.

Gene

A valid fragment of DNA. If the nucleotide is the letter of genetic information, then the gene is a sentence composed of these letters, they control the shape and behavior of the organism. In other words, a gene is like a program that lets a creature know when to make or do something, such as growing an eye or a leg, or repairing a wound.

Allele

A variety of different forms of a creature in a gene. For example, the human allele that controls the color of the iris includes the green-eyed gene and the brown-eyed gene.

Genome Group

A complete set of genes for a particular organism.

Genetic engineering

A method that considers the addition or deletion of a part of a organism's original genes.

Mutation

an event in which a gene in a DNA sequence changes suddenly.

Introduction to Genetics