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

מכיוון שתאים מתחלקים לעתים קרובות, הם חייבים גם לשכפל לעתים קרובות את הגנום שלהם. במהלך תהליך זה, טעויות יכולות להתרחש אשר מובילות לשכפול אזורים של DNA. 
אם מקטע משוכפל של דנ"א מכיל אזור קידוד אחד או יותר, זה נקרא שכפול גנים. משוחרר מהאילוצים שהוטלו על הגן המקורי כדי לשמור על תפקודו, עותק הגן יכול כעת לרכוש מוטציות ועשוי להתפתח כדי למלא תפקיד חדש בתוך התא. אנו מתייחסים לגנים שהתפתחו באופן זה - באמצעות שכפול גנים קיימים בגנום של מין יחיד - כ"פרלוגים". 
אורתולוגים, לעומת זאת, הוא מונח המשמש לתיאור גנים במינים שונים שצמחו מאב קדמון משותף אך המשיכו להתפתח לאחר אירוע התמיינות אחד או יותר. 
המונח "הומולוג" יכול להיות מיושם בשני המקרים, ופשוט מתאר גנים עם אב קדמון משותף. קבוצות של גנים הומולוגיים נקראות ביחד "משפחות גנים".
בגלל הדנ"א הקשור אליהם ודמיון החלבונים הנובע מכך, גנים במשפחת גנים אחת מייצרים בדרך כלל חלבונים המבצעים תפקידים דומים. 
לדוגמה, המוגלובין ומיוגלובין הם חלבונים קשורים אשר שניהם מבצעים קשירת חמצן ביונקים. עם זאת, המוגלובין התפתח כמולקולת הובלת חמצן עיקרית, בעוד שתפקידו של מיוגלובין הוא באחסון חמצן.
כאשר בוחנים רצפי גנום, לעתים קרובות ניתן לזהות ולסווג משפחות גנים כאלה בשל הדמיון הגבוה בין הרצפים. 
בנוסף, חקר משפחות גנים יכול לסייע בהשערת תפקודו של גן חדש שהתגלה גם בהיעדר חלבון.

<ol>
	<li>מזההPDB אחד: 1GZX 
	Paoli, M., Liddington, R., Tame, J., Wilkinson, A., Dodson, G. (1996) מבנה גבישי של T State Haemoglobin עם חמצן קשור בכל ארבעת Haems. J מול ביול 256: 775</li>
	<li>2מזהה PDB: 3RGK 
	האברד, ס.ר., למברייט, ס.ג., בוקסר, ס.ג., הנדריקסון, ו.א. (1990) מבנה גבישי רנטגן של מוטנט מיוגלובין אנושי רקומביננטי ברזולוציה של 2.8 אמפר. J מול ביול 20: 215-218 DOI: 10.1016/S0022-2836(05)80181-0</li>
	<li>H.M. ברמן, ג 'יי ווסטברוק, Z. Feng, ג 'גילילנד, T.N. Bhat, H. Weissig, I.N. Shindyalov, P.E. בורן. (2000) בנק נתוני החלבונים מחקר חומצות גרעין, 28: 235-242</li>
	<li>D. Sehnal, A.S. Rose, J. Kovca, S.K. Burley, S. Velankar (2018) Mol*: לקראת ספרייה משותפת וכלים לגרפיקה מולקולרית באינטרנט MolVA/EuroVis Proceedings. doi:10.2312/molva.20181103</li>
	<li>ס. צ'נג, ג'יי אשלי, ג'יי. ד Kurleto, M.Lobb-Rabe, Y.J. פארק, R.A. Carrillo, E. Özkan (2019). הבסיס המולקולרי של ספציפיות סינפטית על ידי קולטני אימונוגלובולינים ממשפחת העל בדרוזופילה. eLife 2019; 8:e41028 DOI: 10.7554/eLife.41028</li>
</ol>

משפחות גנים

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משפחות גנים מורכבות מקבוצות של גנים המוצעים שמקורם באב קדמון משותף. בדרך כלל גנים אלה מתרחשים בעקבות אירועים שבהם גן או גנים משוכפלים בטעות במהלך חלוקת התא. בניגוד לגנים האביים שלהם (שנתונים ללחץ בחירה כדי לשמור על תפקוד), עותקי גנים אלה אינם צריכים לשמר את הרצפים שלהם ועשויים להתפתח יחסית בקצב מהיר יותר.

מדי פעם ניתן להתאים את האזורים הללו למלא תפקידים חדשים בתוך האורגניזם, ולהפוך לגנים חדשים בפני עצמם. כאשר זה קורה, אנו מתייחסים לגנים הללו פרלוגים - שני גנים בתוך אותו מין שהתפתחו מגן קדמון משותף.

מונח נפוץ נוסף כאשר מתייחסים לבני משפחת גנים הוא אורתולוג. גנים אורתולוגיים הם אלה שנבעו מגן קדמון משותף אך המשיכו להתפתח לאחר אירוע מיון אחד או יותר. לדוגמה, לגן לאנזים העכבר טרהלאז יהיה אורתולוג בבני אדם שמייצר גם את האנזים טרהלאז. עם זאת, הגנים הללו והמוצרים שלהם יהיו שונים לפחות בחלקם ברצף עקב שנות השינוי האבולוציוני מאז העכבר האחרון והאב הקדמון המשותף האנושי. לכן, הם אורתולוגים מאותה משפחת גנים.

המונח הנפוץ השלישי בשימוש במשפחות גנים הוא גנים הומולוגיים. מונח זה רחב יותר ומתייחס לכל הגנים הקשורים במשפחת הגנים.

בנוסף, המונח משפחת-על משמש לעתים כדי להתייחס לקבוצות גדולות מאוד של גנים וחלבונים המציגים מספיק הומולוגיה כדי להיות בעלי מוצא משותף. עבור משפחות גדולות אלו, הקיבוץ עשוי להסתמך על קווי דמיון מכניסטיים כדי לקבוע את היקף הקבוצה. כתוצאה מההתחלה הגנטית המשותפת שלהם, הגנים בתוך משפחת גנים מבצעים בדרך כלל פונקציות קשורות. משפחת העל של האימונוגלובולינים, למשל, כוללת מספר רב של גנים המקודדים הן לחלבונים מסיסים והן לחלבונים משטח התא המעורבים בתגובות אימונולוגיות כמו קשירת תאים או הידבקות. המאפיין המרכזי של משפחה זו הוא שהחברים חולקים תחום משותף הנקרא קפל האימונוגלובולינים - שהוא קריטי לתפקודם.

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משפחות גנים מורכבות מקבוצות של גנים שהוצע כי מקורם באב קדמון משותף. בדרך כלל אלה נובעים באמצעות אירועים שבהם גן או גנים ...

Education

JoVE Core

Molecular Biology

ביולוגיה מולקולרית

Unit 1

יחידה 1

DNA, Cells, and Evolution

DNA, תאים ואבולוציה

KEY TERMS AND CONCEPTS

מונחים ומושגים מרכזיים

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 showcases the molecular processes of the cell through clear and concise animated video lessons. Additionally, in scientist-in-action videos, these concepts' application is demonstrated through real experiments in modern laboratories.

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 ...

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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

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Limits to Natural Selection

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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

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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

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The Fossil Record

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Convergent Evolution

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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

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