{"id":23742,"date":"2023-03-13T13:22:55","date_gmt":"2023-03-13T17:22:55","guid":{"rendered":"https:\/\/genomequebec.com\/?post_type=educative-content&p=23742"},"modified":"2025-10-06T14:00:39","modified_gmt":"2025-10-06T18:00:39","slug":"du-gene-a-la-proteine","status":"publish","type":"educative-content","link":"https:\/\/genomequebec.com\/en\/educative-content\/educational-space\/learn-more\/du-gene-a-la-proteine\/","title":{"rendered":"From gene to protein"},"content":{"rendered":"\n

Genes: Recipes for proteins<\/strong><\/h3>\n\n\n\n

A gene is a unit of DNA that codes for a protein<\/a> or part of a protein. To make a protein, the cell uses a gene\u2019s precise sequence of nitrogenous bases<\/a> (A, T, C and G<\/a>) as a guide.<\/p>\n\n\n\n

Essential for the survival of all living organisms, proteins come in a wide variety of forms and functions. For example, variations in pigmentation proteins are what give panda bears their unique black-and-white coat. The opsin proteins in the eyes of bees are sensitive to ultraviolet light and flower patterns invisible to the human eye, which is crucial for flower pollination.<\/p>\n\n\n\n

The genome can be compared to a cookbook filled with recipes, as it contains many genes that each produce a particular protein.<\/p>\n\n\n\n

Alleles: Recipe variants<\/strong><\/h4>\n\n\n\n

When one or more of a gene\u2019s nitrogenous bases differ, these variants are called alleles<\/a>.<\/p>\n\n\n\n

For example, eyes can have alleles that contain information to create brown, blue, green or grey pigment. <\/p>\n\n\n\n

Gene expression <\/strong><\/strong><\/h4>\n\n\n\n

All of an organism\u2019s cells contain identical DNA. However, only the sections that a specific cell needs to function are expressed. This is what makes cells (such as neurons or muscle cells) different based on their roles in the body.<\/p>\n\n\n\n

The ways cells package their DNA depending on the sections they need to access is referred to as epigenetics<\/a>. When a gene is activated, its DNA is transcribed into RNA. This messenger RNA is then translated by ribosomes into a functional protein.<\/p>\n\n\n\n

Thanks to this precise regulation, each gene is expressed at the right time and in the right place in the organism.<\/p>\n\n\n\n

Did you know?<\/strong><\/strong><\/h4>\n\n\n\n

The size of an organism\u2019s genome does not correlate to its complexity.<\/p>\n\n\n\n

For example, the human genome has around 3.2 billion base pairs, while the largest known genome belongs to the\u202fTmesipteris oblanceolata <\/em>fern, which has 160 billion base pairs!<\/p>\n\n\n\n

Human<\/td>Paris Japonica<\/em><\/td>Tmesipteris oblanceolata<\/em> <\/td>Nasuia deltocephalinicola<\/em> (a bacterium)<\/td>Arabidopsis Thaliana<\/em><\/td><\/tr>
3.2 billion base pairs<\/td>149 billion base pairs<\/td>160 billion base pairs <\/td>112,000 base pairs<\/td>115 million base pairs<\/td><\/tr><\/tbody><\/table>
Sources: The Human Genome Project pieced together only 92% of the DNA \u2013 now scientists have finally filled in the remaining 8% (theconversation.com)<\/a>, The Chemistry of Arabidopsis thaliana<\/em> – ScienceDirect<\/a>, A 160 Gbp fork fern genome shatters size record for eukaryotes: iScience (cell.com)<\/a><\/figcaption><\/figure>\n\n\n\n
Learn more<\/strong> <\/strong><\/summary>\n

Only 1% of our genome directly codes for protein synthesis. The rest, called the non-coding genome, plays a role in gene regulation. These DNA regulatory regions, such as enhancers, promoters and other sequences, regulate gene expression. In genes, promoters are binding sites located right beside the start site for transcription, which is when DNA is copied into RNA. Enhancers increase the activity of certain genes, sometimes at a distance from the transcription<\/a> start site.
Proteins called transcription factors direct the timing and intensity of gene activation and deactivation, which is why some cells express certain genes more than others, why not all cells produce the same proteins, and why cells have different functions.
Studying and understanding these regulatory regions is an important part of genomics research.
Source: The Human Genome Project pieced together only 92% of the DNA \u2013 now scientists have finally filled in the remaining 8% (theconversation.com)<\/a><\/p>\n<\/details>\n\n\n\n

<\/div>\n\n\n\n

Protein synthesis<\/strong><\/h3>\n\n\n\n

Cells synthesize proteins using DNA as a kind of guide or recipe book. <\/p>\n\n\n\n

Steps in protein production:  <\/strong> <\/strong><\/h4>\n\n\n\n
    \n
  1. The DNA<\/a> information to create a protein (the gene<\/a>) is copied into messenger RNA<\/a> (mRNA).<\/li>\n\n\n\n
  2. The mRNA then leaves the nucleus<\/a>, enters the cytoplasm<\/a> and binds to a ribosome<\/a>.<\/li>\n\n\n\n
  3. The ribosome moves to the rough endoplasmic reticulum<\/a> (RER), where it reads the mRNA sequence and assembles the amino acids<\/a> into a polypeptide chain.<\/li>\n\n\n\n
  4. Once complete, the chain is released into the RER, where it is processed and folded into a protein.<\/li>\n\n\n\n
  5. Proteins are carried by transport vesicles from the RER to the Golgi body<\/a>.<\/li>\n<\/ol>\n\n\n\n

    The Golgi body processes the proteins before sending them to the cell surface or into the cytoplasm. The Golgi body also adds chemical tags to classify the new proteins according to their final destination.<\/p>\n\n\n\n

    Proteins that will be secreted out of the cell or embedded into the cell membrane are packaged into transport vesicles that bud from the Golgi body. These vesicles fuse with the cell membrane, and the protein is either released from the cell or delivered into the membrane.<\/p>\n\n\n\n

    \"\"<\/figure>\n\n\n\n

    Protein structure<\/strong><\/p>\n\n\n\n

    Proteins are made of amino acids<\/a> that bind in a specific order to create polypeptide chains.<\/p>\n\n\n\n

    When a protein is being made, its polypeptide chain must fold up into a specific three-dimensional shape so that the protein can function properly and fulfill its role. An error in the protein\u2019s amino acid sequence or shape can impact its function and cause a problem for the organism.<\/p>\n\n\n\n

    \n Accordions<\/span>\n \n \n
    \n Accordion<\/span>\n

    Transcription (in eukaryotes) <\/h3>\n \n\n

    In eukaryotic<\/a> cells, the first step in protein production involves locating the target gene, i.e. the DNA\u2011sequence \u201crecipe\u201d that codes for the desired protein.<\/p>\n\n\n\n

    Once the gene is located, the DNA sequence is copied into a molecule called messenger RNA (mRNA). RNA is similar to DNA but has only a single strand and has uracil (U) nitrogenous bases instead of thymine (T) nitrogenous bases. The process to create the DNA copy is called transcription<\/a>, which is orchestrated by a number of proteins.<\/p>\n\n\n\n

    Unlike DNA, mRNA can leave the cell nucleus and travel to the ribosomes<\/a>, which are structures in the cytoplasm<\/a> that translate information from mRNA.<\/p>\n\n\n<\/div>\n\n \n\n\n<\/div>\n\n\n\n

    Codons: Three-letter codes<\/strong><\/h4>\n\n\n\n

    Codons are sequences of three nitrogenous bases that make up DNA that code for a particular amino acid. The order of the nitrogenous bases in each codon is very important. For example, C-A-C codes for the amino acid histidine, whereas C-C-A codes for the amino acid proline. As a comparison, the words \u201cpare\u201d and \u201cpear\u201d in a recipe book may have the same letters, but their different order means something important for how our recipe will turn out. <\/p>\n\n\n\n

    \n Accordions<\/span>\n \n \n
    \n Accordion<\/span>\n

    Translation (in eukaryotes) <\/h3>\n \n\n

    Ribosomes are organelles that \u201cread\u201d mRNA one codon after another to make the backbone for the protein (the polypeptide chain). Ribosomes are like cooks who read and interpret recipes to make proteins.<\/p>\n\n\n\n

    With each codon, an amino acid is added to the polypeptide chain until all the codons have been read and the ribosome reaches a stop codon on the mRNA. Stop codons mark the end of the coding sequence and signal to the ribosomes to stop synthesizing the protein and release the newly created polypeptide chain.<\/p>\n\n\n\n

    At the end of the translation process, the polypeptide chain may be further modified; for example, it may be folded into its functional three-dimensional structure or receive specific chemical groups. These are called  post-translational modifications.<\/p>\n\n\n\n

    <\/p>\n\n\n\n

    \n
    The cell<\/a><\/div>\n<\/div>\n\n\n<\/div>\n\n \n\n\n
    \n Accordion<\/span>\n

    Alternative splicing <\/h3>\n \n\n

    Alternative splicing is when a single gene codes for different proteins.<\/p>\n\n\n\n

    After DNA is transcribed into mRNA, the mRNA is spliced so that some of its sections (introns<\/a> and exons<\/a>) can be added or removed.<\/p>\n\n\n\n

    Exons are the coding sections of mRNA that determine the amino acid sequence of the final protein. Introns are non-coding sections that are not involved in forming the amino acid sequence.<\/p>\n\n\n\n

    Through this mechanism, the same gene can create different mRNA molecules that will translate into different proteins.<\/p>\n\n\n\n

    To illustrate splicing, let\u2019s take the word EPICUREAN. If we remove some of its letters, we can form the words EPIC, CURE, PAN, RAN and so on. The same thing happens when genes are spliced. Some of the information is kept while other parts are removed to produce different copies of mRNA, which in turn produces different proteins.<\/p>\n\n\n\n

    <\/p>\n\n\n\n

    \"\"<\/figure>\n\n\n<\/div>\n\n \n\n\n
    \n Accordion<\/span>\n

    Protein folding <\/h3>\n \n\n

    A protein\u2019s three-dimensional shape is what determines its function.<\/p>\n\n\n\n

    There are four different stages of folding that produce the protein\u2019s final shape:<\/p>\n\n\n\n