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

- [Istruttore] Oltre alle
complesse disposizioni

di materiale genetico
all&#x27;interno del nucleo cellulare,

i geni umani mostrano anche
la loro unica organizzazione.

Sparsi nei cromosomi vi
sono oltre 20 000 geni

a volte separati da lunghi
filamenti di DNA non codificante.

O che non codifica per proteine.

La chiave dell&#x27; organizzazione
di un singolo gene

&#xE8; il promotore,

a cui si attaccano strutture

in special modo la RNA polimerasi.

Quando questo enzima trova

un sito di inizio trascrizione vicino

comincia a generare filamenti di RNA

utilizzando il DNA come modello.

La polimerasi poi attraversa
il materiale genetico

e continua a produrre RNA

fino a quando non incontra

la sequenza di terminazione
della trascrizione di un gene

e cos&#xEC; termina il processo.

E&#x27; importante notare che fra
questi punti di inizio e fine,

ci sono aree chiamati introni ed esoni,

le cui copie sono entrambe
contenute nel RNA prodotto.

Tuttavia, processi successivi
rimuovono gli introni

da questo trascritto.

Poich&#xE9; questo RNA verr&#xE0;
usato per generare proteine,

gli esoni denotano regioni codificanti

mentre gli introni sono un altro esempio

di materiale non codificante.

E&#x27; interessante notare che altri
tipi di DNA non codificante

come i silenziatori,

sono anch&#x27;essi associati a geni.

Certe proteine chiamate repressori

si legano a queste regioni

prevenendo il legame della polimerasi

ed inibendo la trascrizione.

Il risultato &#xE8; che i silenziatori

aiutano a regolare l&#x27;espressione genica.

Perci&#xF2; un gene &#xE8; composto
da vari componenti.

Fra loro: un promotore, esoni, introni

ed elementi regolatori,

che insieme contribuiscono

alla produzione di
proteine in una cellula.

1. William Roy, Scott e Walter Gilbert. "L'evoluzione degli introni spliceosomiali: modelli, enigmi e progresso". Nature Reviews Genetics 7, n. 3 (marzo 2006): 211–21. <a href="https://doi.org/10.1038/nrg1807">https://doi.org/10.1038/nrg1807</a>.

organizzazione dei geni

<h4>Panoramica</h4>

I genomi degli eucarioti possono essere strutturati in diverse categorie funzionali. Un filamento di DNA &#xE8; composto da geni e regioni intergeniche. I geni stessi sono costituiti da esoni codificanti di proteine e introni non codificanti. Gli introni vengono asbici una volta che la sequenza viene trascritta in mRNA, lasciando solo esoni a codice per le proteine.

<h4>I geni eucarioti sono separati dalle regioni intergeniche</h4>

Nei genomi eucarioti, i geni sono separati da grandi distese di DNA che non codificano per le proteine. Tuttavia, queste regioni intergeniche portano elementi importanti che regolano l&#x27;attivit&#xE0; genica, ad esempio il promotore in cui inizia la trascrizione, e stimolatori e silenziatori che perfezionano l&#x27;espressione genica. A volte questi siti di legame possono trovarsi lontano dal gene associato.

<h4>Gli esoni che codificano le proteine sono intervallati da Introni</h4>

Mentre i ricercatori studiavano il processo di trascrizione genica negli eucarioti, si sono resi conto che l&#x27;mRNA finale che codifica per una proteina &#xE8; pi&#xF9; corto del DNA da cui deriva. Questa differenza di lunghezza &#xE8; dovuta a un processo chiamato splicing. Una volta che il pre-mRNA &#xE8; stato trascritto dal DNA nel nucleo, lo splicing rimuove immediatamente gli introni e unisce gli esoni insieme. Il risultato &#xE8; l&#x27;mRNA codificante delle proteine che si sposta verso il citoplasma e viene tradotto in proteina.

<h4>Il numero di Introni per gene pu&#xF2; variare in modo significativo</h4>

Uno dei pi&#xF9; grandi geni umani, DMD, &#xE8; lungo pi&#xF9; di due milioni di coppie di basi. Questo gene codifica la distrofina della proteina muscolare. Le mutazioni nella DMD causano distrofia muscolare, un disturbo caratterizzato da un progressivo deterioramento muscolare. Questo gene contiene 79 esoni e 103 introni. Dall&#x27;altra parte dello spettro si trova il gene H1A tono: &#xE8; uno dei geni pi&#xF9; piccoli del genoma umano a soli 781 coppie di basi a lungo con un esone e nessun introne.

<h4>Gli Introni hanno funzioni importanti</h4>

Gli introni hanno il DNA spazzatura che deve essere rimosso? &#xC8; interessante notare che gli introni possono trasportare elementi importanti per la regolazione genica. Inoltre, il taglio della trascrizione iniziale e la ri-unione degli esoni permette di mischiare le sequenze di DNA. Questo processo di miscelazione e corrispondenza degli esoni &#xE8; noto come splicing alternativo. Permette di produrre diverse varianti proteiche da un&#x27;unica sequenza di codifica.

<h4>La stragrande maggioranza del genoma umano non codifica per le proteine</h4>

Sapevi che il 99% del tuo genoma non codifica le proteine? Nei primi giorni della ricerca sul genoma, i biologi hanno coniato il termine accattivante &#x22;DNA spazzatura&#x22; per queste sequenze apparentemente non funzionali. Nel frattempo, abbiamo imparato che gran parte del DNA non codificante svolge funzioni importanti. Almeno il 9% del genoma umano &#xE8; coinvolto nella regolazione genica, ovvero nove volte di pi&#xF9; rispetto alle sequenze di codifica delle proteine.

Organizzazione dei geni

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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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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3.1.9-12.B

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3.1.9-12.C

Genes, Introns, and Regulatory DNA

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