Transcripción
Descripción general
La transcripción es el proceso de síntesis de ARN a partir de una secuencia de ADN mediante la ARN polimerasa. Es el primer paso e…
- [Narrador] La transcripción es el proceso
de sintetizar ARN a partir de una plantilla de ADN.
En el núcleo, el complejo de
preiniciación de la transcripción.
se ensambla alrededor del promotor central de un gen,
que incluye un sitio de unión al factor
de transcripción general aquí
en una caja TATA, un sitio de unión para la ARN polimerasa,
y el sitio de inicio de la transcripción.
Una vez unidos los componentes necesarios,
El complejo de preiniciación desenrolla
un corto tramo del ADN.
arriba del sitio de inicio de la transcripción, y la ARN
polimerasa comienza a producir una nueva cadena de ARNm.
Los nucleótidos se añaden uno por uno.
y se produce la síntesis del ARNm
en una dirección de cinco primos a tres primos
leyendo desde el hilo de la plantilla.
Esta nueva cadena de ARNm
Representa una copia de la información
en la cadena de codificación.
Excepto las timidinas son sustituidas por uracilos.
La síntesis continuará hasta
se encuentra una secuencia de terminación,
que liberará el ARNm recién hecho
y permitir un procesamiento posterior.
View the full transcript and gain access to JoVE Core videos
Q1: What is transcription and how does it begin?
Transcription is the process of synthesizing RNA from a DNA template. In the nucleus, the transcription preinitiation complex assembles around the core promoter, which includes a TATA box, an RNA polymerase binding site, and the transcription start site. Once components bind, the preinitiation complex unwinds DNA upstream of the start site, and RNA polymerase begins producing mRNA.
Q2: How does RNA polymerase synthesize mRNA during transcription?
RNA polymerase adds nucleotides one by one to synthesize mRNA in the five prime to three prime direction, reading from the DNA template strand. The newly created mRNA represents a copy of the coding strand information, except thymidines are replaced by uracils. Synthesis continues until a termination sequence is encountered, releasing the mRNA for further processing.
Q3: What types of RNA molecules can be produced by transcription?
Transcription produces different kinds of RNA molecules beyond messenger RNA. In eukaryotes, DNA is transcribed into pre-mRNA that becomes mature mRNA for protein synthesis. Transcription also produces microRNAs, transfer RNA (tRNA), and ribosomal RNA (rRNA), all of which contribute to protein synthesis in cells.
Q4: How does transcriptional regulation control cellular differentiation?
Transcriptional regulation determines cellular differentiation by controlling which genes are turned on or off in specialized cells. DNA-binding proteins called transcription factors orchestrate this process, activating or repressing genes that determine cellular fate. For example, during vertebrate development, induction signals activate transcription factors that direct ectoderm cells to become either skin cells or nervous system cells.
Q5: Why do organisms need to adjust transcription in response to environmental changes?
Organisms must respond to environmental changes such as temperature, precipitation, and food availability by adjusting transcription levels of large numbers of genes. These adjustments modify key traits like growth rates, immunity, and behavior. For instance, plants exposed to drought quickly adjust transcription of hundreds of genes to increase root growth and scavenge water from soil.
Q6: What is the relationship between transcription and protein synthesis?
Transcription is the first step in producing a protein from a gene sequence. RNA polymerase synthesizes mRNA from the DNA template, and this mRNA serves as the genetic instructions for protein synthesis. In prokaryotes, translation can begin while transcription is ongoing, but in eukaryotes, the pre-mRNA undergoes processing before translation occurs.
Q7: How do all cells in the human body have the same genetic information but different functions?
Although all cells contain the same genetic information, they assume diverse forms and functions through regulation of transcription during development. Transcriptional regulation controls which genes are expressed in each cell type, determining whether a precursor cell becomes a neuron, muscle cell, or other specialized cell. This selective gene expression orchestrated by transcription factors enables cellular differentiation.
Copyright © 2026 MyJoVE Corporation. All rights reserved