Name: genes, introns, and regulatory dna
Uploaded: 2026-08-26T08:20:12.834Z
Duration: 2 min 39 s
Channel: JoVE

K12 Standards

Pennsylvania State Academic Standards

9-12

Life Science

Structure and Function

3.1.9-12.A

Organization of Genes

- [Instructor] Junto
con el arreglo complejo

de material gen&#xE9;tico en
el n&#xFA;cleo de una c&#xE9;lula,

los genes humanos tambi&#xE9;n
demuestran su propia y

&#xFA;nica organizaci&#xF3;n.

Dispersos entre los cromosomas
hay m&#xE1;s de 20,000 genes,

a veces separados por
vastas extensiones de

ADN no codificante,

o que no codifican prote&#xED;nas.

Clave para la organizaci&#xF3;n
de un gen individual

es su promotor, mecanismo al cual,

especialmente el ARN
polimerasa, se puede unir.

Cuando esta enzima reconoce un

sitio de iniciaci&#xF3;n de
transcripci&#xF3;n cercano,

comienza a generar una hebra de ARN,

utilizando el ADN como plantilla.

La polimerasa luego atraviesa
el material gen&#xE9;tico,

y sigue produciendo ARN

hasta que identifique la secuencia de

terminaci&#xF3;n de la transcripci&#xF3;n de un gen,

deteniendo el proceso.

Es importante destacar
que entre estos principios

y los puntos finales se
encuentran &#xE1;reas llamadas

intrones y exones,

ambos de los cuales se
reflejan en el producto de ARN.

Sin embargo, los procesos
posteriores eliminan los intrones

de esta transcripci&#xF3;n.

Dado que este ARN se utilizar&#xE1;
para generar prote&#xED;nas,

los exones se denotan como
regiones de codificaci&#xF3;n,

mientras que los intrones
son otro ejemplo de

material no codificante.

Curiosamente, otros tipos
de ADN no codificante

como los silenciadores
tambi&#xE9;n se asocian con genes.

Las prote&#xED;nas llamadas represores
se unen a estas regiones,

previniendo la asociaci&#xF3;n
polimerasa-promotor,

inhibiendo la transcripci&#xF3;n.

Como resultado, los
silenciadores ayudan a regular la

expresi&#xF3;n g&#xE9;nica.

As&#xED;, un gen consta de varios componentes.

Entre ellos un promotor, exones, intrones,

y elementos reguladores,
que en conjunto ayudan a

a determinar la expresi&#xF3;n
de prote&#xED;nas en una c&#xE9;lula.

1. William Roy, Scott y Walter Gilbert. "La evolución de los intrones espliceosomales: patrones, rompecabezas y progreso". Nature Reviews Genetics 7, no. 3 (marzo de 2006): 211–21. <a href="https://doi.org/10.1038/nrg1807">https://doi.org/10.1038/nrg1807</a>.

organización de genes

<h4>Descripci&#xF3;n general</h4> Los genomas de los eucariotas se pueden estructurar en varias categor&#xED;as funcionales. Una cadena de ADN est&#xE1; compuesta por genes y regiones interg&#xE9;nicas. Los propios genes constan de exones que codifican prote&#xED;nas e intrones no codificantes. Los intrones se eliminan una vez que la secuencia se transcribe a ARNm, dejando solo los exones para codificar las prote&#xED;nas. <h4>Los genes eucari&#xF3;ticos est&#xE1;n separados por regiones interg&#xE9;nicas</h4> En los genomas eucariotas, los genes est&#xE1;n separados por grandes extensiones de ADN que no codifican prote&#xED;nas. Sin embargo, estas regiones interg&#xE9;nicas contienen elementos importantes que regulan la actividad gen&#xE9;tica, por ejemplo, el promotor donde comienza la transcripci&#xF3;n y potenciadores y silenciadores que afinan la expresi&#xF3;n g&#xE9;nica. A veces, estos sitios de uni&#xF3;n pueden ubicarse lejos del gen asociado. <h4>Los exones que codifican prote&#xED;nas est&#xE1;n intercalados por intrones</h4> Mientras los investigadores investigaban el proceso de transcripci&#xF3;n gen&#xE9;tica en eucariotas, se dieron cuenta de que el ARNm final que codifica una prote&#xED;na es m&#xE1;s corto que el ADN del que deriva. Esta diferencia de longitud se debe a un proceso llamado empalme. Una vez que el pre-ARNm se ha transcrito a partir del ADN en el n&#xFA;cleo, el corte y empalme elimina inmediatamente los intrones y une los exones. El resultado es un ARNm codificante de prote&#xED;nas que se desplaza al citoplasma y se traduce en prote&#xED;nas. <h4>El n&#xFA;mero de intrones por gen puede variar significativamente</h4> Uno de los genes humanos m&#xE1;s grandes, el DMD, tiene m&#xE1;s de dos millones de pares de bases de largo. Este gen codifica la prote&#xED;na muscular distrofina. Las mutaciones en la DMD causan distrofia muscular, un trastorno caracterizado por un deterioro muscular progresivo. Este gen contiene 79 exones y 103 intrones. En el otro extremo del espectro se encuentra el gen de la histona H1A: es uno de los genes m&#xE1;s peque&#xF1;os del genoma humano con solo 781 pares de bases de largo, un ex&#xF3;n y ning&#xFA;n intr&#xF3;n. <h4>Los intrones llevan funciones importantes</h4> &#xBF;Son los intrones ADN basura que es necesario eliminar? Curiosamente, los intrones pueden transportar elementos que son importantes para la regulaci&#xF3;n gen&#xE9;tica. Adem&#xE1;s, cortar la transcripci&#xF3;n inicial y volver a unir los exones permite mezclar las secuencias de ADN. Este proceso de mezclar y combinar exones se conoce como empalme alternativo. Permite producir varias variantes de prote&#xED;nas a partir de una &#xFA;nica secuencia codificante. <h4>La gran mayor&#xED;a del genoma humano no codifica prote&#xED;nas</h4> &#xBF;Sab&#xED;as que el 99% de tu genoma no codifica prote&#xED;nas? En los primeros d&#xED;as de la investigaci&#xF3;n del genoma, los bi&#xF3;logos acu&#xF1;aron el t&#xE9;rmino pegadizo &#x201C;ADN basura&#x201D; para estas secuencias aparentemente no funcionales. Mientras tanto, hemos aprendido que una gran parte del ADN no codificante desempe&#xF1;a funciones importantes. Al menos el 9% del genoma humano participa en la regulaci&#xF3;n gen&#xE9;tica&#x2013; es decir, nueve veces m&#xE1;s que las secuencias que codifican prote&#xED;nas.

Organización de genes

Overview

The genomes of eukaryotes can be structured in several functional categories. A strand of DNA is comprised of genes and intergenic regions. ...

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Education

Educación

JoVE Core

Biology

Biología

Genetics

Genética

DNA Structure and Function

Estructura y función del ADN

KEY TERMS AND CONCEPTS

TÉRMINOS Y CONCEPTOS CLAVE

genes, introns, and regulatory dna

Eukaryotic genes are arranged within DNA along with non-coding regions that help control gene activity. A DNA strand includes genes and intergenic regions, which are the stretches between genes. These regions do not code for proteins, but they can contain important regulatory elements such as promoters, enhancers, and silencers.

A gene itself is not a single continuous coding block. It usually contains protein-coding exons and non-coding introns. After DNA is transcribed into pre-mRNA in the nucleus, splicing removes the introns and joins the exons together. The shorter mRNA then moves to the cytoplasm, where it is translated into protein.

The number of introns in a gene can vary a lot. The human DMD gene is more than two million base pairs long and encodes dystrophin, a muscle protein. Mutations in DMD can cause muscular dystrophy, a disease that leads to progressive muscle deterioration. This gene has 79 exons and 103 introns. In contrast, the histone H1A gene is only 781 base pairs long and has one exon and no introns.

Introns are not always useless DNA. Some introns contain elements that help regulate genes. They also support alternative splicing, a process that mixes and matches exons after transcription. This lets one coding sequence produce several protein variants.

Most of the human genome does not code for proteins. Early genome research called many of these sequences junk DNA, but scientists now know that much of this non-coding DNA has important roles. At least 9% of the human genome is involved in gene regulation, which is far more than the protein-coding portion.

Genes, Introns, and Regulatory DNA

the dna helix

How DNA Stores Genetic Information

DNA stores genetic information that is passed from one generation to the next in organisms and most viruses. It is built from two strands of nucleotides that twist together into a double helix. The story of how scientists uncovered this structure developed step by step over nearly a century. Each DNA strand is made of nucleotides. A nucleotide contains the sugar deoxyribose, a phosphate group, and one of four nitrogen bases: adenine (A), guanine (G), cytosine (C), or thymine (T). Adenine and...

dna packaging

Chromatin and Histones in DNA Packing

Eukaryotic cells must pack long DNA molecules into the nucleus, and chromatin makes that possible. DNA wraps around proteins called histones to form nucleosomes, which are the main unit of DNA packaging. Nucleosomes then coil into compact chromatin fibers. The amount of DNA in a cell is much larger than it first seems. A single human skin cell has about 3 billion base pairs of DNA, and if that DNA were stretched out in a line, it would be about 2 meters long. With about 50 trillion cells in...

organization of genes

Eukaryotic genes are arranged within DNA along with non-coding regions that help control gene activity. A DNA strand includes genes and intergenic regions, which are the stretches between genes. These regions do not code for proteins, but they can contain important regulatory elements such as promoters, enhancers, and silencers. A gene itself is not a single continuous coding block. It usually contains protein-coding exons and non-coding introns. After DNA is transcribed into pre-mRNA in the...

karyotyping

Chromosome Stains for Detecting Disorders

Chromosome staining helps scientists find genetic disorders by showing the number and physical features of chromosomes. These features appear after DNA condenses into chromosomes during mitosis. Cytogeneticists then stop mitosis and stain the chromosomes to study their banding pattern. The pattern reveals details such as chromosome number, shape, and type. A chromosome description like this is called a karyotype. To create one, scientists take an image of the stained chromosomes and identify...

replication in prokaryotes

How Prokaryotic DNA Is Copied

Prokaryotic DNA is copied through a coordinated process with three main stages: initiation, elongation, and termination. It begins when initiator proteins bind to the single origin of replication, or ori, on the cell’s circular chromosome. The DNA then copies around the circle in both directions, starting from two replication forks, and this produces two DNA molecules. Several proteins work together to open and protect the DNA during replication. Topoisomerase cuts one side of the...

replication in eukaryotes

Eukaryotic DNA Copying and Telomeres

Eukaryotic DNA copying is tightly regulated and must duplicate many linear chromosomes before cell division. The process is highly conserved and uses many proteins with specialized roles. It moves through initiation, elongation, and termination, and it ends with two complete sets of chromosomes in the nucleus. Eukaryotic replication shares basic steps with prokaryotic DNA replication, but the larger genome and linear chromosomes require more proteins. Replication begins at multiple origins of...

proofreading

DNA Polymerase Fixes Replication Errors

DNA polymerase helps copy DNA and fix mistakes during replication. It adds nucleotides in a sequence that matches the template DNA strand. The enzyme also has a higher affinity for the correct base, which helps keep DNA replication accurate. As new genomic DNA is made, it is synthesized in the 5’ to 3’ direction. In many cells, DNA polymerases have different jobs in this process. DNA polymerase delta and DNA polymerase epsilon can proofread when nuclear DNA is being copied. These polymerases...

mismatch repair

DNA Mismatch Repair in Replication

DNA mismatch repair fixes copying errors that happen during DNA replication. When DNA polymerase makes a mistake, the cell can detect a wrong base pair, such as A with G or T with C, and replace it with the correct nucleotide. This repair system works in both prokaryotes and eukaryotes and depends on several proteins. The Mutator protein family plays a central role in this process. In bacteria such as Escherichia coli, MutS first binds the mismatch. MutL then helps identify which strand is the...

nucleotide excision repair

DNA Damage Repair by Excision

DNA damage repair by excision protects cells from mutagens that can change DNA. Exposure to environmental mutagens can create bulky lesions that bend the double helix or block transcription. If these changes are not repaired, they can lead to mutations and may contribute to cancer or disease, depending on which DNA sequences are affected. Nucleotide excision repair, or NER, is the process that detects and removes this kind of damage. Specialized proteins scan the DNA for a damaged region, then...

mutations

DNA Changes From Point Mutations to UV Damage

Mutations are changes in the DNA sequence. They can happen by chance during DNA copying, or they can be caused by environmental factors such as radiation and chemicals. Scientists also describe mutations by how much DNA they affect, how they change a protein, and whether they happen in body cells or germline cells. Some mutations affect only one nucleotide, which is a point mutation. When a point mutation falls inside a gene, the outcome depends on how the amino acid sequence changes. A silent...

transcription

Transcription and Gene Control

Transcription and gene control explain how cells make RNA from DNA and decide which genes are active. RNA polymerase copies a DNA sequence into RNA, and this is the first step in making a protein from a gene. Many other proteins and control sequences help make messenger RNA, or mRNA, correctly. In eukaryotes, the DNA is first copied into a primary RNA, also called pre-mRNA. This RNA can then be processed into mature mRNA, which serves as the template for protein synthesis. In prokaryotes such...

translation

Protein Synthesis and mRNA Decoding

Protein synthesis begins when ribosomes decode messenger RNA (mRNA) and build a chain of amino acids. This final step of gene expression is called translation. The finished chain is a polypeptide, which can later become a functional protein. Proteins are often called the building blocks of life because they make up much of the body, from muscle fibers to hairs and immune system parts. The instructions for each protein are encoded in genes found in the DNA of every cell. In biology, the central...

bacterial transformation

Griffith’s Mouse Experiment and DNA

Bacterial transformation explains how DNA can move into bacteria and change their traits. Frederick Griffith first noticed this in 1928 while studying pneumonia-causing Streptococcus pneumoniae in mice. He compared one pathogenic strain with one non-pathogenic strain and found that only the pathogenic strain killed the host mice. Griffith made an unexpected discovery when he killed the pathogenic bacteria and mixed their remains with live, non-pathogenic bacteria. The mixture killed the mice,...

key terms and concepts

Explore how eukaryotic genes are organized with exons, introns, intergenic regions, and regulatory DNA, plus how splicing and alternative splicing work.

Genes, Introns, and Regulatory DNA | JoVE K12

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New Jersey Student Learning Standards for Science

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DNA Packaging

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3.1.9-12.B

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3.1.9-12.C

Genes, Introns, and Regulatory DNA

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