What is a gene? A complete guide to genes 28th November 2021 – Tags: ,


We are all familiar with genetics or gene, which is made up of DNA. Many young people will have first learned about genetics and DNA from the legendary film Jurassic Park, which talked about DNA and genetics to create dinosaurs. However, humans also have DNA, and for us, it can influence everything around us.

Everyone has DNA, and therefore everyone has genes. Genes are the basic physical and functional units of heredity, they are made up of DNA and you get them from your parents.

The way we understand gene is often shaped by what we know in popular culture, unless you are a scientist. Movies, television and even games talk about genes and how they influence who we are.

However, here we won’t tell you that you can genetically engineer a dinosaur, or that genetic mutations will lead to a zombie outbreak. Here we are going to tell you the truth about genetics and how it really affects your life and who you are as a person.

What is a gene?

Genes are inherited, are made up of DNA, and some act as instructions for making protein molecules. However, many genes do not code for proteins, and in humans genes vary in size from a few hundred DNA bases to millions.

The chromosomes are made up of long strands of DNA with many genes. So DNA is in genes, genes are in chromosomes, and chromosomes are inside the nucleus of cells. Each chromosome is thus a single, long DNA molecule, and this DNA contains very important genetic information.

Genes can vary in complexity; each unique living thing can have different shapes and numbers of chromosomes. For example, humans have 23 pairs of chromosomes, with a total of 46 chromosomes. A hedgehog will have 44 and a fly will have only 4.

Genes have a purpose, the storage of information, and each individual gene has the information needed to build specific proteins that are needed. Our genomes as humans contain 20,687 protein-coding genes. We are more complex beings than you might think.

Genes also come in different forms, which are known as alleles. In our case, the alleles of certain genes come in pairs, with one on each chromosome. If the alleles of a given gene are the same, the organism is called homozygous, and if they are different, heterozygous. The phenotype is determined by how the alleles are combined. Blue eyes may be the result of one allele, while brown eyes may be the result of another allele. The final eye colour depends on which alleles are present and how they interact with each other.

The instructions in your genes will determine your traits, such as eye colour, hair colour, height, and so on. There are different types of genes for each trait. One variant of a gene may have the instructions for brown hair, while another may have the instructions for blonde hair. The outcome will be determined by how these genes interact.

Genes are contained in chromosomes and most human cells contain 23 pairs, a pair of sex chromosomes that can be XX in females, or XY in males. One of the chromosomes in each pair comes from the female parent and the other from the male. This is what makes children often resemble their parents, and why they will often inherit the diseases that run in their families. So, the next time you go to the doctor and he or she asks you “does diabetes run in your family?”, you know that it’s because of the genes your parents carry and that they can contain defects, such as diabetes. But more on that later.

Genes are also the blueprints that build the chemical machinery that keeps our cells alive, whether the genetics are in a human being, an animal, or even a plant. But the number of genes a living thing has does not predict any complexity – in fact, humans have almost 11,000 fewer genes than a water flea!

Our genetic material contains more than just genes – the way cells read and interpret genetic instructions is actually much more complex in humans than in the gene-rich water fleas mentioned above.

To understand genes well, we also need to understand DNA, as they are interconnected. DNA resembles a spiral staircase, known as a double helix, and a total of three billion rungs connect the two outer supports. The rungs are known as base pairs after the two chemicals that make them up. Scientists refer to each of these chemicals by their initials: A, which is adenine, C, which is cytosine, G, which is guanine, and T, which is thymine. A will always be paired with T, and C will always be paired with G.

Hearing this, we might assume that genes do all the hard work to make us who we are, but this is not entirely true. In DNA, genes do not do all the hard work, and it is actually the protein that is produced from them that carries out the functions of the information they carry. Genes can often produce multiple proteins, one or none, some will produce something else called RNAS, which have an entirely different functional job.

Scientists working with genes often understand them best by giving them unique names, gene names can be long and so they often abbreviate the name or give them a unique title. A good example of this is that a gene on “chromosome 7” is associated with cystic fibrosis, and its scientific name is “cystic fibrosis transmembrane conductance regulator”, but it’s a bit long, so they just call it CFTR. So, if you mingle with the scientists, you can understand that a lot of information related to the gene is encoded. It’s too long to talk about genes without using abbreviations and codes.

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genetics gene

What is a gene made up of?

Inside your body, almost every cell is a DNA chemical, genes are a short section of DNA. Genes and DNA work together. Genes are short sections of DNA, and DNA is made up of countless small chemicals called bases. The chemicals can be of type A, C, T or G.

Each gene is a part of this DNA that is made up of an A, C, T, G sequence. Your body will have about 20,000 genes, but about 3,000,000,000,000 of these tiny chemical bases. The set of these bases and genes is what makes up your individual genome.

What makes up your genes and your genome is individual, and it is unique to you, as it contains traceability links through your family, and not just links to your parents and grandparents, but to your distant ancestors. It is therefore possible to trace your ancestry back hundreds of years.

mutation gene

A gene is made up of four types of chemicals (As, Cs, Ts and Gs).

Genes are made up of a long combination of four nucleotide bases/chemicals. These chemicals are Adenine, Cytosine, Guanine and Thymine.

Different combinations of these four chemicals will give people different characteristics. This means that a person with the combination ATCGTT might be born with blue eyes, while another person with the combination ATCGCT might be born with brown eyes.

So what genes do is carry these ACGT codes, and each person has thousands of genes and therefore billions of these codes. Genes are very much like a computer program that provides the individuality of the person to whom they belong.

Genes are a small section of a long double helix molecule of DNA, which has the linear sequence of base pairs we talked about earlier. A gene is therefore any section along the DNA with instructions for proteins to trigger action.

Genes belong to and contain deoxyribonucleic acid, which is DNA, except in some viruses, which are made up of ribonucleic acid (RNA).

Every DNA molecule is made up of two nucleotide chains that resemble a spiral staircase; the sides of this “staircase” are made up of sugars and phosphates. The rungs are made up of the linkage pairs of ACGT codes. These are linked together. An A-code in one chain will bind to a T-code in the other, which forms the rungs. Then, a C in one string will link to a G in the other.

ACTGs contribute to endowing human beings with several characteristics

The GGCAs are genes, in a sense, the way the four bases of DNA are put together, which are the codes A, C, G and T, is called genetic coding. They are combined so that our body’s cellular machinery, the ribosome, can read them and turn them into proteins that will then act according to the instructions of the genes.

In the most basic terms, the genes store the information and the ACTGs are strung together so that our body can read this information and pass it on to the proteins, which will follow the instructions. If our body were an IKEA bookshelf, the company is the genes, which store the information on how to build it, the instruction manual is the ACTG coding that tells you directly how to build it, and the proteins are the person who is actively building the bookshelf.

The genes and the ACTGs are like the filing cabinets and the textbooks, holding the information for those active proteins that take the information and turn it into a reality. These proteins perform a whole range of different tasks in your cells, they will affect the colour of your eyes, boost your muscles, attack invading bacteria, and so on. Some cells will use genes that contain information about how to make keratin, which is a protein that binds inside your body and produces your hair and nails.

Your whole body is basically the result of proteins working hard following the instructions given to them by the ACGT codes, which get their stored information from your genes.

Each of these individual cells and chemicals are equally important to making you who you are, and they work together to create your uniqueness, from the colour of your eyes to your hair, nails, skin, immune system and much more. Everything in your body is a direct result of the genes, ACGTs and proteins that work together to build your body.

What is a genetic mutation?

A genetic mutation is a change in the DNA sequence, mutations can result from DNA copying errors that are made during cell division, exposure to ionising radiation can also mutate, as well as exposure to chemicals called mutagens, or even virus infections. There are germline mutations that occur in eggs and sperm and these mutations can be passed on to offspring, whereas somatic mutations can occur in body cells and are not passed on to offspring.

Mutations in genetics are completely random and at the same time not random at all. The consequences of a mutation do not influence the fact that a mutation occurs, but can occur randomly so that its effects are useful. This means that beneficial changes in DNA do not usually occur, since an organism could benefit from it. Basically, if an organism gets a beneficial mutation in its lifetime, this information will not flow into the organism’s germline DNA. This was observed by Charles Darwin, and it was something he hit the nail on the head.

However, mutations are not always equally likely to occur. Some may occur more frequently than others, as they are preferred by lower-level chemical reactions. These reactions are often also the reason why mutations are an inescapable probability for any organism that can reproduce.

In general, genetic mutations are both random and non-random at the same time. In reality, the randomness of mutations depends on the parents and the individual cells.

gene mutations

A change in one or more genes

Mutations are abnormal changes in the DNA of a gene, the building blocks of our DNA are called bases and the sequence of the bases determines the gene and how/what it functions. Mutations simply involve changes in the arrangement of these bases that make up a gene (bases A, C, G, T). Even a single subtle change in one base, among all the thousands of bases that make up a gene, can have a major effect. It’s a bit like the butterfly effect, where one small thing can have a big impact.

A genetic mutation can affect the cell in multiple ways, for example, some mutations can prevent a protein from being created. Others may change the protein that is produced so that it doesn’t work as it should, or it may simply be a questionable protein that doesn’t work at all.

When a mutation occurs, it may have no appreciable effect, or there is a chance that it may cause a disease. A good example of this is when a particular mutation occurs in the haemoglobin gene, the result is a disease called sickle cell anaemia.

Mutations in cells can also sometimes lead to cancer, it often takes a multitude of mutations before a cell becomes a cancer cell, these mutations could affect different genes that control cell division and growth. We also have genes that are called tumour suppressor genes, and you can guess what a mutation might do to them. Mutations can also cause some normal genes to cause cancer.

Mutated genes can cause disorders or diseases. In popular culture, such as in movies, TV and games, genetic mutations often lead to zombies – any zombie movie, or games like Resident Evil, touch on this and talk about genetics. However, a genetic mutation will not turn you into a monster like in Resident Evil, but could do nothing, or could result in anaemia, diabetes, and in some cases more serious conditions like cancer.

There are various scales of mutations, for example, a small-scale mutation is a change in one base of the DNA sequence. For example, if the original sequence was “TAACTGCAGGT”, but the point mutation occurred and ended up as “TAACCGCAGGT”, this is a small scale, as the second base T has become a C base. There is also another type called substitution, where one or more bases in the sequence are replaced by the same number of bases, but a different base. Thus, if cytosine is replaced by adenine, this is a base substitution mutation.

There is also inversion substitution, where a segment of a chromosome is inverted end to end. In this case, “TAACTGCAGGT” could become “TAACACGTGGT”. Another possibility is insertion, which is when a base is added to a sequence, extending it. Or deletion, when a base is removed from a sequence, making it shorter.

It is also possible for mutations to occur on a much larger scale. These can be as severe as CNV (copy number variation), which is the insertion, repetition or loss of large pieces of DNA. These pieces can be between 10,000 and 5,000,000 bases. Gene duplication, the deletion of large areas of a chromosome and the loss of one copy of a gene in an organism that previously had two copies can also occur.

We can inherit mutations, as our genes are a copy of our parents. If there is a mutation in one of the genes we receive from them, it can be passed from parent to child along with the other genes.

Small inherited changes are capable of making big differences for us. So cystic fibrosis is often caused by a mutation that loses three of the letters of a gene we know as CFTR. However, although mutations are common, inherited diseases are rare indeed, because the diseases we inherit usually need two copies of this mutated gene for the disease to become active.

Cause the loss of one or more genes

Gene deletion occurs when one or more bases are removed from the sequence. It is also possible for entire genes and even entire chromosomes to be deleted. Deletions involve the loss of DNA sequences. The effects of these deletions depend on the size and location of the deleted sequences. Deletions spanning a centromere can result in an acentric chromosome that is likely to be lost during a cell division. Both duplications and deletions can affect gene dosage and will therefore have different outcomes in the individual.

Note that the greater the loss, the more genes are likely to be involved, and the more genes involved, the more drastic the defect.

Some genes require two copies of the same gene to function normally; in cases like this, if one copy remains and one copy is lost, the result is a mutant phenotype.

There is also the possibility of monosomy, the loss of one chromosome in a cell; “mono” means “one” in Greek and people with monosomy have only one copy of a chromosome in their cells instead of the usual two. A common condition caused by this is Turner’s syndrome, which is also known as monosomy X.

Rearrangement of genes/complete chromosomes

There are many ways in which a gene or chromosome can be completely rearranged. Obviously, as mentioned above, there are cases where a deletion or duplication can occur. However, these are not necessarily complete rearrangements. Translocation, on the other hand, can be. A translocation occurs when a piece of a chromosome breaks off and attaches to another chromosome. This is considered a balanced rearrangement, where no genetic material is gained or lost within the cell. If there is a gain or loss, it is considered unbalanced.

A rearrangement can also be an inversion. When a chromosome breaks in two places, the resulting combination has a piece of DNA inverted and reinserted into the sequence. It is possible that genetic material will be lost as a result of this. In a more serious example, dicentric chromosomes are an almost complete rearrangement. Normal chromosomes will have one centromere, a dicentric chromosome will have an abnormal fusion of two chromosome pieces, each with one centromere. This type of fusion is unstable and, as a result, some of the genetic material may be lost.

Finally, ring chromosomes are also a possibility, usually occurring when a chromosome breaks in two places, usually at the ends of the p and q arms, the arms fuse and form a ring. When this happens there may or may not be a centromere, and most of the time the genetic information is lost near the ends of the chromosome.

The function of a gene

Genes decide virtually everything about a living thing, whether it is a person, an animal or a plant. One or several genes can easily affect a specific trait. Genes can also interact with an individual’s environment and will change what the gene produces. Affecting hundreds of internal and external factors, they can influence eye colour, hair colour, skin colour and the diseases or conditions a person may develop, as well as possible inherited weaknesses.

Diseases such as sickle cell anaemia and Huntington’s disease are inherited and are also affected by genetics.

A parent carries a genetic mutation through an egg or sperm and passes it on to his or her child:

(Genetic conditions: diseases that run in families, e.g. sickle cell anaemia and cystic fibrosis).

Genes play a role in almost all health conditions and characteristics, but there are also some conditions where genetic changes are directly responsible for causing a condition. Scientists and doctors call these genetic disorders and inherited diseases.

Genes are passed on from parents to children, so any changes in the DNA of a gene are also passed on to offspring. However, it is possible for DNA changes to occur spontaneously, appearing seemingly out of nowhere for the first time in the child, while the parents are unaffected. This is a new mutation.

It is possible for such a mutation to cause errors in protein instructions, which can result in a protein that does not do its job properly or, in more severe cases, cannot be made at all. When this happens, a genetic disorder occurs.

Scientists have discovered more than 10,000 genetic conditions.

Scientists believe that more than 10,000 conditions are actually caused by changes in individual genes. These can arise from a gene change that occurs spontaneously during the formation of the egg, sperm or during conception, it can also occur when a changed gene is passed from a parent to a child causing health problems either at birth or later in life, or a changed gene is passed from parent to child, causing a genetic susceptibility to a particular condition.

It also affects human metabolism, e.g. calorie consumption.

Genes can also affect your weight, so when you see some people who are bigger or smaller than you, be aware that this may be due to genetics, as genes can affect how calories are used. Some people’s bodies will use calories efficiently, needing fewer calories to fuel their bodies, which can cause excess calories to be stored as fat.

Other people’s bodies will use the calories less efficiently, needing more calories to fuel the body, so there will be fewer calories to store as fat. This would be considered a high metabolism, and efficient storage would be considered a low metabolism.

Scientists are discovering other genetic variants, for example in the development of diabetes and Alzheimer's disease.

As science improves, it has discovered that other genetic variants exist, and it is possible (though not always) to be more susceptible to developing diabetes, Alzheimer’s and dementia due to genetics. Inheriting dementia through a single gene mutation is rare, however it is believed that genes play some role in almost all cases of dementia.

Similarly, family history is not necessary for an individual to develop Alzheimer’s, however, if you have a family member with Alzheimer’s, you are more likely to develop the disease than those who do not have an immediate family member with the disease.

However, diabetes is more directly genetic. If you are a man with type 1 diabetes, your child’s chances of getting it are 1 in 17; if you are a woman with type 1 and your child was born before you were 25, the child’s risk is 1 in 25. If your child was born after the age of 25, the risk is 1 in 100. However, if you had diabetes before the age of 11 and if both you and your partner have type 1 diabetes, the risk is 1 in 10 and 1 in 4.


Genetics affects every aspect of our lives and every bit of who we are. Our health is largely affected by our genetics and there is nothing we can change about it.

Genes are made up of DNA and contribute to the proteins in our body, influencing how we look and our immune system. Your genetics are passed down from your parents, and theirs from theirs.

Genetic diseases and conditions can be inherited, although not all cases of an inherited disease are influenced by a parent having the same disease – genes can sometimes only increase susceptibility.

Genes have the chemicals A, C, G, T which form the link between your DNA and genetics, the way these function will influence your functioning, and your individuality.

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