Genes, DNA, and Chromosomes Overview


Genetics is a branch of science that studies inherited genes and patterns . This includes studying chromosomes (the structures within cells that contain genes) and DNA (the building blocks of genes).

By understanding how genes work and how they affect human health, scientists are increasingly able to identify the causes of disease, predict the risk of certain diseases, and develop drugs that can attack specific cells, including cancer.

This article explains the difference between DNA, genes, and chromosomes, including how they are related and the role they play in each person's individual genome.

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What is a genome?

The best way to understand genetics is to decipher the genome of an organism. The genome is the complete set of genetic instructions for an organism. It contains all the information necessary to build this organism, allowing it to grow and develop. It determines the physical characteristics of the body and how certain cells, tissues and organs function.

The genome consists of three parts:

  • DNA : the molecule that provides the body's genetic instructions.
  • Genes : collection of DNA encoded to produce specific proteins.
  • Chromosomes , structures within cells that contain genes.

Almost all living organisms have a genome, which includes bacteria, plants, birds, fish, and mammals. Some species contain more genes than others. For example, the human genome consists of approximately 20,000 to 25,000 genes. The genome of bacteria consists of a single strand of DNA.

Although the genome of each species is different, each organism within that species has its own unique genome. That is why no two people are exactly the same.


The genome is a complete set of genetic instructions, made up of DNA, genes, and chromosomes. Each genome is unique; No two are the same.

What is DNA?

Simply put, DNA (short for deoxyribonucleic acid ) is the building block of our genes.

Within DNA there is a unique chemical code that determines a person's growth, development, and function. The code is determined by the location of four chemical compounds known as nucleotide bases. Four bases:

  • Adenine (A)
  • Cytosine (C)
  • Guanine (G)
  • Moment)

The bases connect to each other, A to T and C to G, to form units known as base pairs. The vapors then combine with sugar and phosphate molecules to form what ultimately looks like a spiral staircase known as a double helix. The particular order or sequence of the foundations determines what instructions are given to build and maintain the body.

Human DNA is made up of approximately 3 million of these bases, 99% of which are the same for all humans. The remaining 1% is what distinguishes one person from another.

Almost all cells in the human body have the same DNA.


DNA is the building block of genes found in almost all cells. DNA is made up of four chemical compounds called bases, which provide coded instructions for building and maintaining an organism. Depending on the location of these bases, the instructions will vary from person to person.

What is a gene?

A gene is a separate piece of cellular DNA that is encoded for a specific purpose. Some genes act according to instructions for the production of proteins, the building blocks of tissues, and the body's source of energy. Different proteins play different roles in the structure, function, and regulation of the body's tissues and organs.

Other genes are coded to make RNA ( ribonucleic acid ), a molecule that converts information stored in DNA into protein.

Genes are the basic physical unit of heredity. The way they are coded ultimately determines your physical characteristics and how your body functions. Each person has two copies of each gene, one inherited from each parent.

The different versions of a gene are called alleles. The alleles you inherited from your parents can determine whether you have brown or blue eyes. Other alleles are directly related to diseases such as cystic fibrosis or Huntington's disease , while others can still increase the risk of certain diseases, such as breast cancer .

Genes make up between 1% and 5% of the human genome. The rest is made up of uncoded DNA called "junk DNA," which does not make proteins, but rather helps regulate gene function.


A gene is part of a cell's DNA that is programmed to make a specific protein. The way a gene is encoded will determine the physical traits and characteristics of a person. Each person has two copies of each gene, one inherited from each parent.

What is a chromosome?

Genes are packed into packages called chromosomes. Humans have 23 pairs of chromosomes for a total of 46 separate chromosomes. Chromosomes are found in the nucleus of almost every cell in the body.

A pair of chromosomes, called X and Y chromosomes, determine whether you are male or female. Women have one pair of XX chromosomes and men one pair of XY chromosomes.

The other 22 pairs, called autosomal chromosomes, define the rest of your body. Some genes on these chromosomes can be dominant or recessive. Priory:

  • Autosomal dominant means that you only need one copy of an allele from one parent to develop a trait (for example, brown eyes or Huntington's disease).
  • Autosomal recessive means that you need two copies of an allele, one from each parent, to develop a trait (for example, green eyes or cystic fibrosis).


Chromosomes are made up of a set of genes. A person has 23 pairs of chromosomes, including one pair of sex chromosomes. The remaining 22 pairs, called autosomal chromosomes, determine the rest of the body composition.

What is genetic variation?

Some people think of genetic variation as mutations, but that's only part of the picture. There are actually three types of genetic variation:

  • A genetic mutation is a change in the DNA sequence. This can be due to copy errors made during cell division, exposure to radiation, exposure to chemicals called mutagens, or infection with certain viruses. Diseases such as sickle cell anemia , Tay-Sachs disease, and phenylketonuria are caused by certain genetic mutations.
  • Genetic recombination is the process by which DNA fragments are broken down, recombined, and repaired to produce a new combination of alleles. Down syndrome is an example of genetic recombination.
  • Genetic migration is an evolutionary process in which the addition or loss of people to a population alters the gene pool, making certain traits less or more common. A hypothetical example is the loss of red-haired people in Scotland, which could eventually lead to fewer and fewer Scottish children being born with red hair.


DNA is the building block of genes in almost all cells, and it contains coded instructions for building and maintaining an organism. Genes are part of cellular DNA that has a specific purpose in the production of specific proteins. Chromosomes are sets of genes passed down from parent to child that ultimately determine the traits and characteristics of that person.

Together, DNA, genes, and chromosomes make up the genome of each organism. Each organism, and each person, has a unique genome.

Get the word of drug information

While genetics can be difficult to understand, it increasingly determines how diseases are diagnosed, treated, or prevented. Many of the tools used in medicine today are the result of a deeper understanding of DNA, genes, chromosomes, and the human genome as a whole.

Today, genetic research has led to the development of targeted drugs that can treat cancer with less damage to non-cancer cells. Genetic testing is available to predict your likelihood of certain diseases so that you can avoid them.

Genetic engineering has even allowed scientists to mass produce human insulin in bacteria and create RNA vaccines similar to those used to treat COVID-19 .

By understanding the general concepts of genetics, you can better appreciate its medical applications and its impact on your health.

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