Gene

Tiny parts in your body tell you how to grow.

These parts are called genes. They pass from parents to their children.

Genes can decide things like your eye color. Some parts of your body work in ways you cannot see. They help your body do many jobs. Genes are like a plan for every living thing. They make sure you are you!

What is a gene? Scientists use this word in two ways.

A Mendelian gene is a unit of heredity. This means it is a way to pass traits from parents to children. Gregor Mendel found this by studying pea plants.

A molecular gene is a part of DNA. DNA is a long molecule that holds your instructions. A gene is a specific sequence of parts called nucleotides. These parts work in a set of steps called gene expression. First, DNA is copied into RNA. RNA can then help make a protein.

Some genes make proteins. Other genes are non-coding. This means they do not make proteins, but they still have a job to do. These jobs can be very important. Genes can also change. These changes are called mutations. A mutation can make a new version of a gene. We call these versions alleles. Alleles can lead to different traits, like eye color. Some traits are easy to see. Other traits, like blood type, are hidden inside you.

A gene is a tiny instruction that makes life work. Scientists use this word in two different ways. One way is called a Mendelian gene. This is a basic unit used to pass traits from parents to their offspring. The other way is called a molecular gene. This describes a specific sequence of parts called nucleotides found in DNA.

These instructions are very important for every living thing. They help decide how an organism grows and looks.

To make things work, genes go through a thing called gene expression. This happens in a few clear steps. First, the DNA is copied into a molecule called RNA. This RNA can then act as a tool all by itself. Or, it can serve as a template to build a protein.

There are two main types of these molecular genes. Some are protein-coding genes that make proteins. Others are non-coding genes that do different jobs. Even if they do not make proteins, they must have a biological function to be called a true gene.

We first learned about these units from Gregor Mendel. Between 1857 and 1864, he lived in the Austrian Empire. He studied 8,000 common edible pea plants to see how traits passed down.

He did not use the word "gene" yet. Instead, he described discrete units that caused physical traits. Later, a scientist named Johannsen introduced the word "gene" in 1909. He wanted a simple name for the things that determine an organism's character.

Genes are not all the same size. In 1965, scientists thought a gene might be 1,500 base pairs long. However, they discovered introns in the 1970s. This showed that many genes are much larger. For example, a typical mammalian protein-coding gene is about 62,000 base pairs long.

There are about 20,000 of these genes in mammals. These genes take up about 35% to 40% of the entire genome. Scientists also found that DNA is the place where this information is kept.

Genes help create your unique identity. Your specific set of genes is called a genotype. This works with your environment to create your phenotype. The phenotype is the set of traits you can actually see.

Some traits are easy to notice, like eye color. Other traits are hidden, like your blood type. Sometimes, a gene can have a mutation. This creates a new version called an allele. These small changes help genes evolve over a long time.

In biology, the term "gene" is used in two primary ways. The Mendelian gene refers to a basic unit of heredity that passes traits from parents to offspring. The molecular gene refers to a specific sequence of nucleotides within DNA. This molecular definition is more common in biochemistry and molecular biology. It describes the gene as a sequence that is transcribed to produce RNA.

Scientists use these different definitions to understand how life functions at both large and small scales.

To understand how a gene works, we must look at the process of gene expression. This is the method by which a cell synthesizes RNA or protein from a gene. First, the DNA sequence is copied into a molecule called RNA through transcription. This RNA molecule can then serve two different purposes. It might be directly functional on its own, or it might act as an intermediate template. This template is used to guide the synthesis of a protein.

There are two main types of molecular genes: protein-coding genes and non-coding genes.

Protein-coding genes are sequences that provide the instructions to build proteins. Non-coding genes are different because they produce functional RNA molecules instead of proteins. Examples of these include ribosomal RNA and tRNA. For a sequence of DNA to be considered a true gene, it must have a biological function. Some stretches of DNA produce transcripts that have no function, such as pseudogenes or "junk RNA" caused by errors. These non-functional sequences do not qualify as true genes.

This distinction is a vital part of modern molecular definitions.

Our understanding of these units began with the work of Gregor Mendel. Between 1857 and 1864, Mendel studied 8,000 common edible pea plants in the Austrian Empire. He tracked how distinct traits moved from parents to their offspring.

While he did not use the word "gene," he described discrete inherited units. His work helped establish the difference between a genotype and a phenotype. The genotype is the specific set of DNA sequences an individual possesses. The phenotype is the set of observable traits, such as eye color or blood type.

In 1909, the scientist Wilhelm Johannsen introduced the term "gene." He wanted a name that was free of complex hypotheses. He chose it to describe the "plans" or "foundations" that determine an organism's character. Later, in the 1940s and 1950s, scientists discovered that DNA is the molecular repository for this information. Researchers like Rosalind Franklin and Maurice Wilkins used X-ray crystallography to study DNA structure. This led James D. Watson and Francis Crick to propose a model of the double-stranded DNA molecule.

This discovery revealed how genetic information could be replicated.

Genes vary greatly in their physical size and complexity. In 1965, scientists estimated a typical gene was about 1,500 base pairs long. However, the discovery of introns in the 1970s changed this view. Introns are parts of a gene that are not part of the final functional product. This meant many eukaryotic genes are much larger than previously thought. For example, a typical mammalian protein-coding gene is about 62,000 base pairs in length. There are approximately 20,000 of these genes in a mammal.

These genes occupy about 35% to 40% of the mammalian genome.

Genes are also subject to change through mutations. A mutation is a change in the DNA sequence that creates a new variant called an allele. These alleles can lead to different phenotypic traits in a population. Over time, genes evolve through processes like natural selection and genetic drift. Sometimes, a gene can even be duplicated. When this happens, the new copy can eventually evolve to perform a completely new function. This constant change is what allows life to adapt and diversify over many generations.