Name: genome size and gene evolution
Uploaded: 2023-04-30T18:28:42.000Z
Duration: 3 min 21 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

heredity-inheritance-and-variation-of-traits

Heredity- Inheritance and Variation of Traits

LS.Bio.6.2

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

Genome Size and the Evolution of New Genes

A pesar de la naturaleza simple del código genético, existe una variación considerable en términos de tamaño del genoma, desde los genomas más pequeños conocidos, incluida la proteobacteria Candidatus Carsonella ruddii con menos de 160 mil pares de bases, hasta los más grandes, como la planta con flores japonesa Paris japonica con alrededor ><de 150 mil millones.
 
A pesar de estos extremos, las bacterias y las arqueas generalmente tienen alrededor de 3.000 genes dentro de sus genomas. Debido a que los procariotas casi no tienen secuencias no codificantes, esto significa que sus genomas pueden ser relativamente pequeños en comparación con los de los eucariotas. Los genomas más pequeños también significan menos para replicar en cada ronda de división celular, lo que tiene sentido logístico para una reproducción rápida.
Los eucariotas suelen tener alrededor de 20.000 genes, pero sus genomas están puntuados por largos tramos de secuencia no codificante, lo que significa que el tamaño de su genoma no se traduce necesariamente en complejidad. 
El genoma de Paris japonica puede ser más de cincuenta veces el tamaño del genoma humano, pero esto se debe, al menos en parte, a grandes cantidades de secuencias no codificantes y probablemente a altos niveles de duplicación, no necesariamente genes más nuevos.
Entonces, ¿cómo evolucionan los organismos nuevos genes? La respuesta suele ser modificando la secuencia que ya existe.
Uno de los principales recursos para que los nuevos genes evolucionen es a través de la duplicación de genes. Imagina que una sección de ADN que contiene un gen se duplica accidentalmente. Ahora el organismo tiene una segunda copia de un gen existente. 
Estas nuevas copias de genes están libres de las restricciones impuestas al original para mantener su función, por lo que pueden divergir, lo que podría evolucionar hacia un papel novedoso o una función modificada del original. 
Otra forma de crear nuevos genes es la mezcla de ADN, en la que los segmentos de un gen existente o una copia de un gen se separan y se mueven para unirse a los de un gen diferente, creando un gen híbrido que puede asumir una nueva función.
Mutación intragénica: los cambios en una secuencia genética introducidos por mutaciones a lo largo del tiempo, explican muchos genes "nuevos". Esta divergencia es más notable cuando se comparan especies o linajes que a su vez divergen de forma independiente. Una vez que esta divergencia está más allá de cierto punto, o un gen adquiere una función nueva, pueden clasificarse como genes completamente diferentes.
Por último, la transferencia horizontal de genes aporta nuevos genes y secuencias al genoma procedentes de fuentes externas, como otros individuos e incluso otras especies. Este tipo de adquisición de genes nuevos es más común en procariotas y arqueas, siendo la transferencia de genes de resistencia a antibióticos un ejemplo bien conocido. 
Si bien es raro en los eucariotas, todavía se considera una fuente esencial de novedad genética, y el material genético puede provenir incluso de especies lejanas relacionadas, como las bacterias y los hongos en este ejemplo.

el tamaño del genoma y la evolución de nuevos genes

Si bien cada organismo vivo tiene un genoma de algún tipo (ya sea ARN o ADN), existe una variación considerable en el tamaño de estos modelos. Un factor importante que afecta el tamaño del genoma es si el organismo es procariota o eucariota.

En los procariotas, el genoma contiene poca o ninguna secuencia no codificante, de modo que los genes están agrupados estrechamente en grupos u operones secuencialmente a lo largo del cromosoma. Por el contrario, los genes de los eucariotas están marcados por largos tramos de secuencias no codificantes. En general, esto contribuye al fenómeno de que los genomas procarióticos tienden a ser más pequeños (es decir, contienen menos bases) en promedio que los de los eucariotas.

Como era de esperar, dada esta observación, los genomas más pequeños conocidos son, en su mayoría, procariotas. Candidatus Carsonella rudii, por ejemplo, es una proteobacteria muy simplificada cuyo genoma tiene un tamaño de sólo 160.000 pares de bases. Habiendo perdido muchos genes que necesitaba para sintetizar proteínas esenciales para la vida, ha evolucionado hasta convertirse en un simbionte intracelular obligado. En el extremo opuesto del espectro, la planta con flores japonesa eucariota Paris japonica es uno de los genomas más grandes conocidos, con alrededor de 150 mil millones de pares de bases. Aunque se desconoce la cantidad de genes que codifica, el genoma muestra grandes cantidades de duplicación y secuencias no codificantes.

Dentro del genoma de un procariota promedio hay, aproximadamente, 3.000 genes. El eucariota promedio tiene alrededor de 20.000. Pero el tamaño del genoma, especialmente en eucariotas, es tremendamente variable, en gran parte debido a la cantidad de secuencia no codificante.

La creación de nuevos genes

Para desarrollar nuevos genes, los organismos tienen algunas opciones principales. Lo único que la mayoría de estos tienen en común es que modifican secuencias que ya existen.

La duplicación juega un papel importante en la creación de nuevos genes y existen algunos tipos de duplicación que pueden dar como resultado estas nuevas secuencias. En la duplicación de genes, se duplica una sección de ADN que contiene un gen. Esta segunda copia no enfrenta la presión de selección que constriñe a la primera, por lo que puede divergir. Con el tiempo, esto puede conducir a la evolución de genes nuevos, con nuevas funciones.

Otro tipo de duplicación, la mezcla de ADN, puede dar lugar a que sólo una sección de un gen se duplique y se una a otro gen. Esto puede dar lugar a la creación de genes novedosos, con productos novedosos.

A veces, nuevos genes simplemente evolucionan a partir de mutaciones acumuladas a lo largo del tiempo. Esto se conoce como mutación intragénica y es más notable cuando se comparan especies o poblaciones divergentes.

Finalmente, también es posible obtener nuevos genes de fuentes externas, en un proceso conocido como transferencia horizontal de genes. Esto significa que se puede incorporar material genético de otros individuos, a veces de la misma especie, pero también potencialmente de otra especie completamente. Esta es una fuente frecuente de genes nuevos en procariotas y arqueas. Es menos común en eucariotas, pero se ha demostrado que ocurre, y los eucariotas pueden incluso recoger información genética de fuentes tan distantes como bacterias u hongos.

El tamaño del genoma y la evolución de nuevos genes

Si bien todos los organismos vivos tienen un genoma de algún tipo (ya sea ARN o ADN), existe una variación considerable en los tamaños de estos planos. Uno de los principales ...

Education

Educación

JoVE Core

Cell Biology

Biología Celular

Unit 1

Unidad 1

Cells, Genomes, and Evolution

Células, genomas y evolución

KEY TERMS AND CONCEPTS

TÉRMINOS Y CONCEPTOS CLAVE

genome size and gene evolution

Genome size and gene evolution are linked through changes in DNA sequence and genome structure. Some genes can arise from parts of the genome that were not coding before, while others come from changes to existing genes. These shifts help explain how new genetic material can appear over time.

A genome is the full set of DNA in an organism. Its size can change as DNA is added, removed, or rearranged. The transcript highlights that genome size is not fixed, and that these changes can shape the evolution of new genes.

New genes may form by duplication and later change, or by other alterations in noncoding DNA. Over time, these changes can give rise to new functions. This process helps connect genome structure with the emergence of genetic novelty.

Genome Size and Gene Evolution

what are cells?

Cells as the Building Blocks of Life

Cells are the basic building blocks of life. A bacterium can be a single cell, while a human is made of trillions of cells. Even with this range, cells share key features that support life. A living cell has a plasma membrane. This is a bilayer of lipids that separates the cytoplasm inside the cell from the outside environment. A cell also carries genetic information in the form of DNA. In prokaryotic cells, DNA is found in a region called the nucleoid. In eukaryotic cells, DNA is enclosed...

the tree of life - bacteria, archaea, and eukaryotes

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

Three Domains on the Tree of Life

The tree of life shows how living things are grouped into three domains: Bacteria, Archaea, and Eukaryotes. This classification helps explain the major branches of life and how they are related. Bacteria and Archaea are both single-celled organisms, but they are not the same. Eukaryotes include organisms with more complex cells, such as plants, animals, and fungi. Together, these three domains give a broad picture of life on Earth. Understanding the tree of life helps students compare cell...

prokaryotic cells

How Prokaryotes Survive Without a Nucleus

Prokaryotes are small unicellular organisms that live without a nucleus. They include the domains Archaea and Bacteria. Bacteria include common microbes such as Salmonella and E. coli, while Archaea include extremophiles that live in harsh places like volcanic springs. Prokaryotic cells still share several basic features with eukaryotic cells. They have a plasma membrane, cytoplasm, ribosomes, and genetic material in the form of single, circular DNA. Their cell parts float freely in the...

eukaryotic compartmentalization

How Organelles Keep Cells Working

Eukaryotic cells keep their organelles separate so each part can do a specific job. Organelles such as the nucleus and mitochondria are surrounded by membranes. These membranes are selectively permeable, which means they control what enters and leaves. That control creates small internal environments with conditions suited to each organelle. These controlled spaces help organelles work more efficiently. In animal cells, lysosomes keep an acidic environment that helps their enzymes digest...

eukaryotic evolution

How Eukaryotic Cells Became Complex

Eukaryotic cells became complex through a debated evolutionary path that likely involved endosymbiosis. The most accepted model is the endosymbiont theory, which explains how organelles such as mitochondria and chloroplasts may have entered an ancestral cell. Other ideas include the nucleus-first hypothesis, the mitochondria-first hypothesis, and the eukaryote-first hypothesis. The nucleus-first hypothesis says an ancestral prokaryote first formed a membrane around its DNA, creating the...

animal and plant cell structure

Plant vs Animal Cell Division and Specialization

Plant and animal cells differ in how they divide, organize into tissues, and specialize for different jobs. Both cell types divide by mitosis in non-gametic cells and by meiosis in gametic cells, but the details are not the same. These differences help explain how each cell type supports growth and reproduction. During cell division, animal cells use centrosomes to organize spindle fibers and separate chromosomes. Plant cells do not have centrosomes. Instead, they use a microtubule-organizing...

cytoplasm

Cytoplasm and the Cell’s Internal Support

The cytoplasm is the cell’s internal space that holds organelles and the cytoskeleton. It is suspended in the cytosol, an aqueous fluid made of water, ions, salts, and many organic molecules. This fluid helps keep the cell organized and supports many cellular activities. The cytoplasm is also where protein synthesis and protein folding take place. The watery cytosol helps proteins fold correctly. In a folded protein, hydrophobic amino acid side chains tend to stay buried in the core, while...

the nucleus

Nuclear DNA, Chromatin, and Nucleoli

The nucleus is a membrane-bound organelle that stores chromosomal DNA and helps control what proteins a eukaryotic cell makes. It acts as the cell’s control center. DNA in mitochondria and chloroplasts is different because it mainly supports functions specific to those organelles. Inside the nucleus, DNA is wrapped around proteins called histones. This DNA-protein complex is called chromatin. During interphase, when the cell is not dividing, chromatin stays loosely arranged so the DNA is easy...

the dna helix

How DNA Structure Was Discovered

DNA is the genetic material that passes traits from one generation to the next in organisms and most viruses. It is made of two strands of nucleotides that twist into a spring-like double helix. The shape is not perfectly even. It also has repeating grooves called the major groove and the minor groove. The major groove forms where the sugar-phosphate backbones are farther apart. This wider space gives DNA-binding proteins, including transcription factors, better access to the bases. The minor...

the central dogma

DNA to Protein: RNA’s Role

DNA to protein flow depends on RNA as the link between genetic information and the amino acids that build proteins. Early scientists knew that DNA stores the information for cell functions and that proteins carry out most of those functions. For a long time, they did not know how the code in DNA became a working protein. At first, many people thought one gene was changed directly into its protein. Two findings in eukaryotic cells challenged that idea. Protein production does not happen in the...

mutations

Mutations in DNA and Inherited Disease

Mutations are changes in the DNA sequence. They can happen on their own during DNA copying, or they can be caused by environmental factors. Scientists describe mutations in several ways, including whether they change the amino acid sequence of a protein, how much DNA they affect, and whether they occur in somatic cells or germline cells. Some mutations are point mutations. A point mutation changes a single nucleotide in DNA. Other mutations are chromosomal alterations, which change the number...

genome size and the evolution of new genes

Genome size and gene evolution are linked through changes in DNA sequence and genome structure. Some genes can arise from parts of the genome that were not coding before, while others come from changes to existing genes. These shifts help explain how new genetic material can appear over time. A genome is the full set of DNA in an organism. Its size can change as DNA is added, removed, or rearranged. The transcript highlights that genome size is not fixed, and that these changes can shape the...

gene families

Shared Origins of Gene Families

Gene families are groups of related genes that share a common origin. They form when genes are copied and then change over time. These related genes can be found within the same genome. The video also connects gene families to homologous genes and orthologous genes. Homologous genes are genes with a shared evolutionary origin. Orthologous genes are homologous genes found in different species. Gene families help show how these relationships are used to study evolution and related gene functions.

gene evolution - fast or slow?

Gene Evolution Rates and Selection

Gene evolution can happen at different rates, and natural selection helps shape those changes. Some genes change slowly because important DNA changes are removed over time. Other genes can change more quickly when different mutations are kept in a population. The rate of evolution depends on how a gene is used and how strongly it is affected by selection. Genes with essential jobs often stay more similar across species. Genes under weaker pressure may show more variation and may evolve faster.<br...

types of genetic transfer between organisms

types-of-genetic-transfer-between-organisms

Vertical and Horizontal Gene Transfer

Genetic transfer between organisms happens in two main ways: vertical gene transfer and horizontal gene transfer. These two routes explain how hereditary material moves from one generation to the next or between organisms that are not parent and offspring. Vertical gene transfer passes genes from parent to offspring during reproduction. This is the usual way genetic information is inherited in living things. Horizontal gene transfer moves genetic material between organisms outside of...

key terms and concepts

Explore how genome size changes can shape gene evolution, including gene duplication, DNA rearrangement, and the rise of new genetic functions.

Genome Size and Gene Evolution | JoVE K12

cell biology

JoVE Core Biología Celular ilustra procesos celulares complejos mediante completos vídeos animados fáciles de entender. Esta colección se centra en los componentes esenciales de las células y su funcionamiento, incluyendo los orgánulos y las membranas, el transporte celular y el metabolismo energético celular. Todo este material se complementa con los vídeos de científicos en acción, que muestran la aplicación de la biología celular en experimentos reales de investigación.

Pennsylvania State Academic Standards

Life Science

Inheritance and Variation of Traits

3.1.9-12.P

3.1.9-12.Q

Louisiana Student Standards for Science

High School

Life Sciences

Biological Evolution: Unity And Diversity

HS-LS4-1

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Ohio’s Learning Standards and Model Curriculum

Heredity

Mutations

Virginia  Standards of Learning

HIgh School

BIO.5

BIO.5.b

Arizona Science Standards

HS.L3

HS.L3U1.25

HS+B.L3

HS+B.L3U1.12

Next Generation Science Standards

Heredity: Inheritance and Variation of Traits

HS-LS3-2

new-york-state-science-learning-standards

New York State Science Learning Standards

HS-LS3-1.

What is Meiosis?

Meiosis is the process by which diploid cells divide to produce haploid daughter cells. In humans, each diploid cell contains 46 chromosomes, half from ...

Meiosis I

Meiosis II

Meiosis vs. Mitosis

Crossing Over

Crossing over is the exchange of genetic information between homologous chromosomes during prophase I of meiosis I. Genetic recombination gives rise to ...

Nondisjunction

Nondisjunction is the failure of homologous chromosomes or sister chromatids to separate correctly and move to the opposite poles of the cells. This ...

Spermatogenesis

Spermatogenesis is the process by which haploid sperm cells are produced in the male testes. It starts with stem cells located close to the outer rim of ...

Oogenesis

In human women, oogenesis produces one mature egg cell or ovum for every precursor cell that enters meiosis. This process differs in two unique ways from ...

Fertilization

During fertilization, an egg and sperm cell fuse to create a new diploid structure. In humans, the process occurs once the egg has been released from the ...

Cleavage and Blastulation

After a large-single-celled zygote is produced via fertilization, the process of cleavage occurs while zygotes travel through the uterine tube. Cleavage ...

Gastrulation

Gastrulation establishes the three primary tissues of an embryo: the ectoderm, mesoderm, and endoderm. This developmental process relies on a series of ...

Neurulation

Neurulation is the embryological process which forms the precursors of the central nervous system and occurs after gastrulation has established the three ...

Cell Migration

Cell migration, the process by which cells move from one location to another, is essential for the proper development and viability of organisms ...

Determination

During embryogenesis, cells become progressively committed to different fates through a two-step process: specification followed by determination. ...

Use models to explain how DNA is passed from parents to offspring through the processes of meiosis and fertilization in sexual reproduction.

LS.Bio.6.1

Mutations are changes in the sequence of DNA. These changes can occur spontaneously or they can be induced by exposure to environmental factors. Mutations ...

Types of Genetic Transfer Between Organisms

Base-pairing and DNA Repair

The DNA Replication Fork

Lagging Strand Synthesis

The Replisome

Proofreading

Synthesis of new DNA molecules is carried out by the enzyme DNA polymerase, which adds nucleotides on the daughter strand complementary to the template ...

Replication in Prokaryotes

DNA replication has three main steps: initiation, elongation, and termination. Replication in prokaryotes begins when initiator proteins bind to the ...

Replication in Eukaryotes

In eukaryotic cells, DNA replication is highly conserved and tightly regulated. Multiple linear chromosomes must be duplicated with high fidelity before ...

Overview of DNA Repair

Base Excision Repair

Nucleotide Excision Repair

DNA Distortion and Damage
Cells are regularly exposed to mutagens&#8212;factors in the environment that can damage DNA and generate mutations. UV ...

Mismatch Repair

Organisms are capable of detecting and fixing nucleotide mismatches that occur during DNA replication. This sophisticated process requires identifying the ...

Fixing Double-strand Breaks

Homologous Recombination

Gene Conversion

Restarting Stalled Replication Forks

Construct an explanation to summarize how inheritable genetic variations may result from: new genetic combinations in meiosis, mutations during replication, or mutations caused by environmental factors.

An Overview of Genetic Analysis

An organism&#8217;s physical traits, or phenotype, are a product of its genotype, which is the combination of alleles (gene variants) inherited from its ...

Genetic Crosses

To dissect genetic processes or create organisms with novel suites of traits, scientists can perform genetic crosses, or the purposeful mating of two ...

Punnett Squares

Monohybrid Crosses

Dihybrid Crosses

Trihybrid Crosses

Trihybrid Crosses
Some of Mendel&#8217;s crosses examined three pairs of contrasting characteristics. Such a cross is called a trihybrid cross. A ...

Law of Independent Assortment

Chi-square Analysis

The chi-square test is a statistical hypothesis test. It is used to check whether there is a significant difference between an expected value and an ...

Pedigree Analysis

Multiple Allele Traits

Incomplete Dominance

Gregor Mendel&#39;s work (1822 - 1884) was primarily focused on pea plants. Through his initial experiments, he determined that every gene in a diploid ...

Lethal Alleles

Agouti: A Lethal Allele
Lucien Cu&#233;not discovered lethal alleles in 1905 while studying the inheritance of coat color in mice. The agouti gene is ...

Polygenic Traits

background-and-environment-affect-phenotype

Background and Environment Affect Phenotype

Although the genetic makeup of an organism plays a major role in determining the phenotype, there are also several environmental factors, such as ...

Use mathematics and computational thinking to predict the variation and distribution of expressed traits based on: Mendelian inheritance, co-dominance, incomplete dominance, multiple alleles, and sex-linked inheritance.

LS.Bio.7.1

Overview

A pedigree is a diagram displaying a family&#x2019;s history of a trait. Analyzing pedigrees can reveal (1) whether a trait is dominant or ...

Probability Laws

Overview

The probability of inheriting a trait can be calculated using the sum and product rules. The sum rule is used to calculate the probability of ...

The Concept of Multiple Allelism

Multiple allelism describes genes that exist in three or more allelic forms. Although diploid organisms, like humans, ...

Analyze and interpret data to explain how polygenic traits result in a wide range of phenotypes.

LS.Bio.7.2

Pleiotropy

Pleiotropy is the phenomenon in which a single gene impacts multiple, seemingly unrelated phenotypic traits. For example, defects in the SOX10 gene cause ...

Nature and Nurture

Many human characteristics, like height, are shaped by both nature&mdash;in other words, by our genes&mdash;and by nurture, or our environment. For ...

Construct an explanation to summarize how traits result from interactions of genetic factors (multiple genes and/or alleles) and environmental factors.

LS.Bio.7.3

PCR: The Polymerase Chain Reaction

The polymerase chain reaction, or PCR, is a technique used to amplify DNA through thermocycling &#8211; cyles of temperature changes at fixed time ...

DNA Gel Electrophoresis

DNA gel electrophoresis is a technique used for the detection and separation of DNA molecules. An electric field is applied to a gel matrix comprised of ...

DNA Isolation

DNA isolation protocols can be fast and straightforward or complex and time-consuming depending on the type and quality of DNA required for further ...

Analyze and interpret data to compare DNA samples.

LS.Bio.8.1

Understand genetic mechanisms for variation.

Genome Size and Gene Evolution

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