Name: how gene families evolve and diversify
Uploaded: 2020-11-23T11:47:33.000Z
Duration: 1 min 57 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 Families

Da sich Zellen häufig teilen, müssen sie auch häufig ihr Genom duplizieren. Dabei kann es zu Fehlern kommen, die dazu führen, dass DNA-Regionen dupliziert werden. 
Enthält ein duplizierter DNA-Abschnitt eine oder mehrere kodierende Regionen, spricht man von einer Genduplikation. Befreit von den Zwängen, die dem ursprünglichen Gen auferlegt werden, um seine Funktion aufrechtzuerhalten, kann die Genkopie nun Mutationen erwerben und sich weiterentwickeln, um eine neue Funktion innerhalb der Zelle zu erfüllen. Gene, die sich auf diese Weise - durch Duplikation vorhandener Gene im Genom einer einzigen Spezies - entwickelt haben, bezeichnen wir als "Paraloge". 
Orthologe hingegen ist ein Begriff, der verwendet wird, um Gene in verschiedenen Arten zu beschreiben, die aus einem gemeinsamen Vorfahren hervorgegangen sind, sich aber nach einem oder mehreren Artbildungsereignissen weiterentwickelt haben. 
Der Begriff "Homolog" kann in beiden Fällen verwendet werden und beschreibt einfach Gene mit einem gemeinsamen Vorfahren. Gruppen homologer Gene werden zusammenfassend als "Genfamilien" bezeichnet.
Aufgrund ihrer verwandten DNA und der daraus resultierenden Proteinähnlichkeiten produzieren Gene innerhalb einer Genfamilie typischerweise Proteine, die ähnliche Funktionen erfüllen. 
Zum Beispiel sind Hämoglobin und Myoglobin verwandte Proteine, die beide die Sauerstoffbindung bei Säugetieren übernehmen. Hämoglobin hat sich jedoch als primäres Sauerstofftransportmolekül entwickelt, während Myoglobin eine Rolle bei der Sauerstoffspeicherung spielt.
Bei der Untersuchung von Genomsequenzen können solche Genfamilien aufgrund ihrer hohen Sequenzähnlichkeit häufig identifiziert und klassifiziert werden. 
Darüber hinaus kann die Untersuchung von Genfamilien dabei helfen, Hypothesen über die Funktion eines neu entdeckten Gens aufzustellen, selbst wenn kein Protein vorhanden ist.

<ol>
	<li>1PDB-Kennung: 1GZX 
	Paoli, M., Liddington, R., Tame, J., Wilkinson, A., Dodson, G. (1996) Kristallstruktur von Hämoglobin im T-Zustand mit Sauerstoffbindung an allen vier Hämen. J Mol Biol 256: 775</li>
	<li>2PDB-Kennung: 3RGK 
	Hubbard, S.R., Lambright, S.G., Boxer, S.G., Hendrickson, W.A. (1990) Röntgenkristallstruktur einer rekombinanten menschlichen Myoglobinmutante mit einer Auflösung von 2,8 A. J Mol Biol 20: 215-218 DOI: 10.1016/S0022-2836(05)80181-0</li>
	<li>H.M. Berman, J. Westbrook, Z. Feng, G. Gilliland, T.N. Bhat, H. Weissig, I.N. Shindyalov, P.E. Bourne. (2000) Die Proteindatenbank Nukleinsäurenforschung, 28: 235-242</li>
	<li>D. Sehnal, A.S. Rose, J. Kovca, S.K. Burley, S. Velankar (2018) Mol*: Auf dem Weg zu einer gemeinsamen Bibliothek und Tools für die Web-Molekulargrafik MolVA/EuroVis Proceedings. doi:10.2312/molva.20181103</li>
	<li>S. Cheng, J. Ashley, J.. D. Kurleto, M.Lobb-Rabe, Y.J. Park, R.A. Carrillo, E. Özkan (2019). Molekulare Grundlagen der synaptischen Spezifität durch Immunglobulin-Superfamilien-Rezeptoren in Drosophila. eLife 2019; 8:e41028 DOI: 10.7554/eLife.41028</li>
</ol>

genfamilien

Genfamilien bestehen aus Gruppen von Genen, von denen angenommen wird, dass sie von einem gemeinsamen Vorfahren abstammen. Typischerweise entstehen diese durch Ereignisse, bei denen ein Gen oder mehrere Gene während der Zellteilung versehentlich dupliziert werden. Im Gegensatz zu ihren Elterngenen (die einem Selektionsdruck unterliegen, um ihre Funktion zu erhalten), müssen diese Genkopien ihre Sequenzen nicht bewahren und können sich relativ schneller entwickeln.

Gelegentlich können diese Regionen angepasst werden, um neue Rollen innerhalb des Organismus zu übernehmen und somit zu eigenständigen neuen Genen werden. Wenn dies geschieht, bezeichnen wir diese Gene als Paraloge – zwei Gene innerhalb derselben Spezies, die von einem gemeinsamen Vorfahrengen abstammen.

Ein weiterer häufig verwendeter Begriff in Bezug auf Mitglieder einer Genfamilie ist Ortholog. Orthologe Gene sind solche, die von einem gemeinsamen Vorfahrengen abstammen und sich nach einem oder mehreren Artbildungsereignissen weiterentwickelt haben. Beispielsweise hätte das Gen für das Enzym Trehalase bei Mäusen ein Ortholog beim Menschen, das ebenfalls das Enzym Trehalase produziert. Diese Gene und ihre Produkte wären jedoch aufgrund der evolutionären Veränderungen seit dem letzten gemeinsamen Vorfahren von Maus und Mensch zumindest teilweise unterschiedlich in ihrer Sequenz. Daher sind sie Orthologe in derselben Genfamilie.

Der dritte häufig verwendete Begriff innerhalb von Genfamilien sind homologe Gene. Dieser Begriff ist breiter gefasst und bezieht sich auf alle verwandten Gene innerhalb einer Genfamilie.

Zusätzlich wird manchmal der Begriff Superfamilie verwendet, um sehr große Gruppen von Genen und Proteinen zu bezeichnen, die genügend Homologie aufweisen, um eine gemeinsame Abstammung zu haben. Bei diesen großen Familien kann die Gruppierung auf mechanistischen Ähnlichkeiten beruhen, um den Umfang der Gruppe zu bestimmen. Aufgrund ihrer gemeinsamen genetischen Entstehung führen die Gene innerhalb einer Genfamilie in der Regel verwandte Funktionen aus. Die Immunglobulin-Superfamilie umfasst beispielsweise eine große Anzahl von Genen, die sowohl für lösliche als auch für zellgebundene Proteine kodieren, die an immunologischen Reaktionen wie Zellbindung oder Adhäsion beteiligt sind. Das Hauptmerkmal dieser Familie ist, dass die Mitglieder eine gemeinsame Domäne teilen, die als Immunglobulin-Faltung bekannt ist und für ihre Funktion entscheidend ist.

Genfamilien

Genfamilien bestehen aus Gruppen von Genen, von denen angenommen wird, dass sie von einem gemeinsamen Vorfahren abstammen. Typischerweise entstehen diese durch Ereignisse, bei denen ein oder mehrere Gene ...

Education

Lehre

JoVE Core

Molecular Biology

Molekularbiologie

Unit 1

Einheit 1

DNA, Cells, and Evolution

DNA, Zellen und Evolution

KEY TERMS AND CONCEPTS

KERNBEGRIFFE UND KONZEPTE

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, which are genes in different species that came from the same ancestral gene and kept evolving after speciation, or the split of one species into separate species.

A mouse trehalase gene, for example, has an ortholog in humans that also makes the trehalase enzyme. Even so, the mouse and human genes, and the proteins they produce, are not identical. They differ at least partly in sequence because of the time since mouse and human shared a common ancestor.

The term homologous genes is broader. It includes all related genes in a gene family. The term superfamily is sometimes used for very large groups of genes and proteins with enough homology, or shared ancestry, to be grouped together. For these large groups, scientists may also use shared mechanism as part of the classification.

Genes in the same family usually do related jobs. One example is the immunoglobulin superfamily. It includes many genes that code for soluble proteins and cell surface proteins involved in immune responses such as cell binding and adhesion. A key feature of this family is a shared domain called the immunoglobulin fold, which is important for function.

How Gene Families Evolve and Diversify

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?

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...

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

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

Learn how gene families form from duplicated genes, and how paralogs, orthologs, and homologous genes are related in evolution and function.

How Gene Families Evolve and Diversify | JoVE K12

molecular biology

JoVE Core Molecular Biology veranschaulicht die molekularen Prozesse der Zelle in prägnanten animierten Video-Lektionen. In Videos von Wissenschaftlern in Aktion wird die Anwendung dieser Konzepte zusätzlich durch reale Experimente in modernen Laboren demonstriert.

new-jersey-student-learning-standards-for-science

New Jersey Student Learning Standards for Science

High School

Life Science

heredity-inheritance-and-variation-of-traits

Heredity: Inheritance and Variation of Traits

HS-LS3-1

Development of Antibiotic Resistance

Antibiotic resistance is a major public health concern that arises when bacteria evolve mechanisms to withstand the effects of antibiotic treatments. This ...

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

Speciation is the evolutionary process resulting in the formation of new, distinct species&#x2014;groups of reproductively isolated populations.The ...

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 ...

Simulating Natural Selection
ExpandTo begin, cut the white, black, and gray pipe cleaners into quarters, which should produce a total of 100 pieces that ...

Artificial Selection

Natural Selection and Adaptive Evolution
In natural settings, adaptive evolution takes place by natural selection, a process in which differences in ...

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

Observing Artificial Selection in Plants 
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

Phylogenetic trees come in many forms. It matters in which sequence the organisms are arranged from the bottom to the top of the tree, but the branches ...

Conditions on Early Earth

Around 4 billion years ago, oceans began to condense on earth while volcanic eruptions released nitrogen, carbon dioxide, methane, ammonia, and hydrogen ...

The Colonization of Land

Changes in the environment of the early Earth drove the evolution of organisms. As prokaryotic organisms in the oceans began to photosynthesize, they ...

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 ...

Gene Evolution - Fast or Slow?

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 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 ...

Diversity and Extinction during the Paleogene Epoch
ExpandBegin this procedure by reading the extinction reading supplement that has been printed out for ...

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

John H. Renwick first coined the term &#8220;synteny&#8221; in 1971, which refers to the genes present on the same chromosomes, even if they are not ...

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

Phylogeny is concerned with the evolutionary diversification of organisms or groups of organisms. A group of organisms with a name is called a taxon ...

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.

How Gene Families Evolve and Diversify

Description

Transcript

Tags

More videos by Standards