Name: why some gene regions evolve faster
Uploaded: 2020-11-23T11:47:33.000Z
Duration: 2 min 5 s
Channel: JoVE

K12 Standards

north-carolina-k-12-science-standard-course-of-study

North Carolina K-12 Science Standard Course of Study

9-12

Biology

Biological Evolution- Unity and Diversity

LS.Bio.9.2

Gene Evolution - Fast or Slow?

La forma en que las mutaciones afectan la supervivencia de una célula depende en gran medida de la ubicación del cambio genético. En regiones del genoma que no codifican genes o regiones reguladoras, las mutaciones pueden tener poco efecto, de modo que la célula a menudo puede continuar como de costumbre.
El efecto general es que las secuencias no codificantes son libres de cambiar con bastante rapidez en términos evolutivos, lo que significa que estas regiones de un genoma pueden ser casi irreconocibles incluso en dos especies estrechamente relacionadas.
Sin embargo, en las secuencias codificantes, las mutaciones no se adoptan tan libremente. Si bien en casos muy raros pueden ser beneficiosos, como una mutación en un gen de una enzima que crea una mejor afinidad de unión al sustrato; la mayoría será perjudicial.
Echemos un vistazo al gen de ARNr 16s, por ejemplo. Codifica un ARN estructural que forma parte del ribosoma. Algunas de las regiones de este ARN son críticas para la función de los ribosomas, y los cambios en estos segmentos son excepcionalmente raros. Estas regiones altamente conservadas cambian tan lentamente que se pueden usar para examinar la homología de secuencia entre filos, reinos e incluso todas las especies vivas, lo que las convierte en una herramienta valiosa para estudiar las relaciones entre organismos incluso distantemente relacionados.
Sin embargo, todavía hay secciones de la secuencia de ARNr 16s menos críticas para funcionar, que pueden evolucionar un poco más rápido. Estas "regiones variables" pueden ser útiles para dilucidar las relaciones entre especies más estrechamente relacionadas, como géneros o incluso cepas de bacterias.
En general, esto conduce al fenómeno de que diferentes regiones del genoma pueden evolucionar a tasas muy diferentes, incluso dentro de regiones que codifican un solo gen.

evolución genética: ¿rápida o lenta?

Los genomas de los eucariotas están marcados por largos tramos de secuencia que no codifican proteínas ni ARN. Aunque algunas de estas regiones contienen secuencias reguladoras cruciales, la gran mayoría de este ADN no cumple ninguna función conocida. Normalmente, estas regiones del genoma son aquellas en las que se observa el cambio más rápido, en términos evolutivos, porque normalmente hay poca o ninguna presión de selección que actúa sobre estas regiones para preservar sus secuencias.

Por el contrario, las regiones que codifican una proteína pueden experimentar una alta presión de selección, porque es probable que cualquier cambio en su secuencia dé como resultado una proteína menos capaz de realizar su función de manera óptima. Sin embargo, ocasionalmente, una mutación en una de estas regiones producirá un resultado beneficioso que contribuye a la aptitud general del organismo y dichas mutaciones a menudo persisten e incluso pueden fijarse en las poblaciones. Cuando se compara la frecuencia de estos eventos de mutación con los cambios relativamente regulares observados en secuencias no codificantes, esto es extremadamente raro y, por lo tanto, en general se considera que las regiones codificantes evolucionan lentamente.

También es cierto que existe una cantidad mensurable de variación en los niveles de conservación de secuencias dentro de las secuencias codificantes, y esto se observa en todos los organismos. Por ejemplo, tomemos el ejemplo de una proteína receptora. Estas proteínas suelen tener diferentes regiones que pueden realizar funciones como la unión a ligandos, la señalización intracelular o la integración en la membrana. En este caso, una mutación en la región implicada en la unión del ligando puede producir una proteína que sea menos eficaz para unirse al ligando. Por lo tanto, la presión de selección probablemente sería alta sobre los nucleótidos particulares que codifican esta parte de la proteína. Sin embargo, en la sección de la proteína que atraviesa la membrana, es posible que se observe menos efecto si se produce una sustitución de aminoácidos y, por lo tanto, niveles más bajos de presión de selección. En estas condiciones, podríamos ver que dos regiones del mismo gen codificador de proteínas podrían tener diferentes ritmos de evolución.

Secuenciación de genes o regiones genómicas para construir filogenias

Esta variación en la velocidad de la evolución del genoma en diferentes regiones puede estudiarse para responder preguntas sobre las relaciones evolutivas. Se pueden seleccionar y secuenciar genes y regiones genéticas en grupos de individuos para responder preguntas tan específicas como "¿son estas poblaciones especies potencialmente diferentes?" o tan amplias como “¿cómo se ubican estos filos en el árbol de la vida?”. Para el primero, seleccionar un gen que tenga una región relativamente ligeramente conservada ayudaría a identificar diferencias a nivel de población. Por el contrario, para responder preguntas sobre grupos tan diversos como los filos, una región genética altamente conservada puede proporcionar suficiente homología para producir una filogenia de dichos grupos. Las regiones comúnmente utilizadas para análisis filogenéticos moleculares como estos incluyen genes de ARNr ribosómico (como ARNr 16s, ARNr 18s o ARNr 28s) o regiones genómicas conocidas como ITS (Espaciadores internos transcritos, I o II) que se encuentran entre la subunidad de ARNr ribosómico. genes.

Evolución genética: ¿rápida o lenta?

Los genomas de los eucariotas están marcados por largos tramos de secuencia que no codifican proteínas o ARN. Aunque algunas de estas regiones contienen ...

Education

Educación

JoVE Core

Molecular Biology

Biología Molecular

Unit 1

Unidad 1

DNA, Cells, and Evolution

ADN, células y evolución

KEY TERMS AND CONCEPTS

TÉRMINOS Y CONCEPTOS CLAVE

why some gene regions evolve faster

Gene regions do not all change at the same rate. In eukaryotes, long stretches of DNA do not code for proteins or RNAs. Some of these non-coding regions include important regulatory sequences, but most have no known function. Because little or no selection pressure acts on them, they often change the fastest over evolutionary time.

Protein-coding regions usually evolve more slowly. A change in a coding sequence can alter a protein and make it less effective at doing its job. That creates strong selection pressure to keep the sequence unchanged. Still, a rare mutation can improve fitness, and those helpful changes may spread through a population and even become fixed.

Rates of change can also differ within the same gene. A receptor protein, for example, may have one part for ligand binding, another for intracellular signaling, and another for membrane integration. A mutation in the ligand-binding region may reduce how well the protein binds its target, so selection pressure there can be high. In the membrane-spanning region, an amino acid change may have less effect, so that part may evolve more slowly or more freely.

These differences in sequence conservation help scientists study evolutionary relationships. Researchers can choose and sequence genes or genomic regions to ask narrow questions, such as whether two populations may be different species, or broad questions, such as how phyla fit into the tree of life. Lightly conserved regions can reveal small differences, while highly conserved regions can still show homology across very distant groups. Common choices for molecular phylogeny include ribosomal rRNA genes such as 16s rRNA, 18s rRNA, and 28s rRNA, as well as ITS regions, or internal transcribed spacers, between the ribosomal subunit genes.

Why Some Gene Regions Evolve Faster

the dna helix

DNA Structure and Base Pairing

DNA has a helical structure that helps store genetic information. The double helix is the shape formed by two strands that twist around each other. This structure is a key feature of DNA in cells. The two strands are held together by base pairing. Bases on one strand match with bases on the other strand in a regular way. This pairing helps keep the DNA molecule stable and organized. The helix shape also helps explain how DNA fits into chromosomes and carries instructions for living things. By...

the central dogma

DNA to Protein: Central Dogma Steps

The central dogma explains how genetic information moves from DNA to RNA to protein. This flow is a key idea in molecular biology. It helps show how cells use genes to make the molecules that carry out work. DNA stores the instructions for making proteins. During transcription, a gene in DNA is copied into RNA. The RNA then carries that message to the next stage. In translation, the RNA message is used to build a protein. Proteins do much of the cell’s work, so this process connects genes to...

prokaryotic cells

Inside Prokaryotic Cell Structure

Prokaryotic cells have a simple internal structure compared with many other cells. They are usually divided into two groups: bacteria and archaea. These cells have no nucleus, so their DNA is not enclosed in a membrane-bound compartment. Instead, the genetic material is found in the nucleoid, a region where the DNA is located in the cell. Some prokaryotic cells also contain plasmids, which are small extra DNA molecules. A capsule may surround the cell and provide an additional outer layer. <br...

eukaryotic compartmentalization

Cell Compartments in Eukaryotes

Eukaryotic cells use compartments to organize many different jobs inside one cell. These compartments help separate processes so they can happen in the right place. The compartment called the cytosol is the fluid part of the cell. It surrounds the other internal structures and helps support many cell processes. Inside the cell, membrane-bound organelles create distinct microenvironments. A microenvironment is a small internal space with conditions that fit a specific task. This separation...

the tree of life - bacteria, archaea, eukaryotes

the-tree-of-life-bacteria-archaea-eukaryotes

How Life Is Classified Into Three Domains

The tree of life shows how organisms are related through evolution. Its root represents the common ancestor of all life on Earth. From that point, branches spread out like a tree. The tips of the branches represent living, or extant, species. Species that no longer exist, called extinct species, appear closer to the center of the tree. Today, these organisms are grouped into three domains: bacteria, archaea, and eukaryotes. Scientists still debate these divisions, so the tree of life keeps...

mutations

How Mutations Change DNA

Mutations are changes in DNA. They can alter the genetic code and affect how genes work. In high school biology, students often study mutations to understand how DNA changes can influence traits. The transcript focuses on two common mutation types: point mutations and frameshift mutations. A point mutation changes one nucleotide, which is one DNA building block. A frameshift mutation happens when nucleotides are added or removed and the reading frame shifts. These changes matter because they...

gene evolution - fast or slow?

Gene regions do not all change at the same rate. In eukaryotes, long stretches of DNA do not code for proteins or RNAs. Some of these non-coding regions include important regulatory sequences, but most have no known function. Because little or no selection pressure acts on them, they often change the fastest over evolutionary time. Protein-coding regions usually evolve more slowly. A change in a coding sequence can alter a protein and make it less effective at doing its job. That creates...

genome size and the evolution of new genes

genome-size-and-the-evolution-of-new-genes

How Genome Size Shapes New Genes

Genome size can vary widely, and it also helps show how new genes form. Every living organism has a genome, whether it uses RNA or DNA. Yet the size of that genome can be very different from one organism to another. One major difference is whether the organism is prokaryotic or eukaryotic. Prokaryotic genomes usually have little to no non-coding sequence, which means genes are packed closely together in operons along the chromosome. Eukaryotic genomes contain long stretches of non-coding DNA...

gene families

How Gene Families Evolve and Diversify

Gene families are groups of genes that are thought to come from a shared ancestor. They usually form when a gene is copied by mistake during cell division. The original gene stays under selection pressure to keep its job, while the extra copy can change more quickly over time. Some copied genes gain a new role in the organism. When that happens, they are called paralogs, which are two genes in the same species that evolved from one common ancestral gene. Gene families also include orthologs,...

types of genetic transfer between organisms

types-of-genetic-transfer-between-organisms

How Genes Move Within and Across Generations

Genetic transfer is the movement of genetic information from one organism to another. It happens in two main ways: vertical gene transfer and horizontal gene transfer. Vertical gene transfer moves genes from one generation to the next. It is much more common than horizontal gene transfer. Vertical gene transfer happens during both sexual reproduction and asexual reproduction. In both cases, one or more organisms pass some or all of their genome to their offspring. This kind of transfer occurs...

key terms and concepts

Explore why non-coding DNA often changes quickly, why coding genes are more conserved, and how scientists use gene sequences to build phylogenies.

Why Some Gene Regions Evolve Faster | JoVE K12

molecular biology

JoVE Core Biología Molecular presenta los procesos moleculares de la célula a través de lecciones claras y concisas de animaciones audiovisuales. Además, en los vídeos de científicos en acción, se muestran aplicaciones de estos conceptos mediante experimentos reales en laboratorios especializados.

Next Generation Science Standards

High School

Life Science

heredity-inheritance-and-variation-of-traits

Heredity: Inheritance and Variation of Traits

HS-LS4-1

Florida Department of Education

SC.912.L.15

SC.912.L.15.2

new-york-state-science-learning-standards

New York State Science Learning Standards

Natural Selection and Evolution

HS-LS4-1.

Development of Antibiotic Resistance

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Understanding Species and Reproductive Barriers

A species is a group of organisms that interbreed and produce fertile offspring. Typically, individuals of the same species appear similar and share ...

Formation of Species

Speciation describes the formation of one or more new species from one or sometimes multiple original species. The resulting species are discrete from the ...

Speciation Rates

Speciation can proceed at markedly different rates, and evolutionary biologists commonly describe these differences through the models of gradualism and ...

Genetics of Speciation

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Hybrid Zones

Hybrid zones are narrow regions where two closely related species interact, mate, and produce hybrids. Relative to either parent species, hybrids may ...

What is Natural Selection?

Natural selection is an evolutionary process in which individuals with survival-promoting traits reproduce at higher rates. These favorable traits become ...

Types of Selection

Natural selection influences the frequencies of particular alleles and phenotypes within populations in several different ways. Primarily, natural ...

Frequency-dependent Selection

When the fitness of a trait is influenced by how common it is (i.e., its frequency) relative to different traits within a population, this is referred to ...

Limits to Natural Selection

Organisms that are well-adapted to their environment are more likely to survive and reproduce. However, natural selection does not lead to perfectly ...

Natural Selection

Fitness
Widespread variation of phenotypes in natural populations provides the raw material for evolution, which is the change in the inherited traits of ...

Simulating Natural Selection
ExpandTo prepare for the lab, set out workstations for each student pair containing 6 white, 6 black, and 13 gray 12 inch ...

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Artificial Selection

Natural Selection and Adaptive Evolution
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Observing Artificial Selection in Plants
ExpandTwo weeks before beginning the pollination experiments, collect a sufficient amount of small pots with a ...

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ExpandTo begin the experiment, collect five two-week old grown plants from the generation one population that ...

Analyze and interpret data to summarize how various factors such as geographic isolation, pesticide resistance, antibiotic resistance can influence natural selection.

LS.Bio.9.1

Phylogenetic Trees

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Conditions on Early Earth

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The Colonization of Land

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What is Evolutionary History?

Scientists record evolutionary history by analyzing fossil, morphological, and genetic data. The fossil record documents the history of life on Earth and ...

The Evidence for Evolution

Genetic variations accumulating within populations over generations give rise to biological evolution. Evolutionary changes can result in the formation of ...

The Fossil Record

The fossil record documents only a small fraction of all organisms that have ever inhabited Earth. Fossilization is a rare process, and most organisms ...

Convergent Evolution

Evolution shapes the features of organisms over time, ensuring that they are suited for the environments in which they live. Sometimes, selection pressure ...

The genomes of eukaryotes are punctuated by long stretches of sequence which do not code for proteins or RNAs. Although some of these regions do contain ...

Genome Size and the Evolution of New Genes

While every living organism has a genome of some kind (be it RNA, or DNA), there is considerable variation in the sizes of these blueprints. One major ...

Gene Families

Gene families consist of groups of genes proposed to have originated from a common ancestor. Typically these arise through events in which a gene or genes ...

Types of Genetic Transfer Between Organisms

Genetic transfer occurs when genetic information is passed from one organism to another. It occurs via two mechanisms: vertical gene transfer and ...

Ribozymes

The term ribozyme is used for RNA that can act as an enzyme. Ribozymes are mainly found in selected viruses, bacteria, plant organelles, and lower ...

Construct an explanation to illustrate how common ancestry and biological evolution are supported by multiple lines of empirical evidence.

Use models to illustrate the conditions required for natural selection, including the overproduction of offspring, inherited variation, and the struggle to survive.

LS.Bio.9.3

Construct an explanation to explain how natural selection leads to adaptations within populations.

LS.Bio.9.4

Extinction

The History of Life on Earth
Fossils of organisms that were different from anything alive today had been documented as early as the 17th century, but it ...

Diversity and Extinction during the Paleogene Epoch
ExpandFirst, familiarize yourself with the extinction reading supplement for the background on what ...

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Construct explanations to illustrate how varying environmental conditions may result in: changes in the number of individuals of a species, the emergence of new species over time, or the extinction of other species.

LS.Bio.10.1

Synteny and Evolution

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Multi-species Conserved Sequences

Next-generation sequencing technologies have created large genomic databases of a variety of animals and plants. Ever since the human genome project was ...

Taxonomy

Taxonomy is the science of defining and naming groups of biological organisms based on shared characteristics. It uses a hierarchy of increasingly ...

Phylogeny

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Use models (including dichotomous keys, scientific nomenclature, cladograms, phylogenetic trees) to identify organisms and exemplify relationships.

LS.Bio.10.2

Understand natural selection as a mechanism for biological evolution.

Why Some Gene Regions Evolve Faster

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