Name: how organelle genomes resemble bacteria
Uploaded: 2020-11-23T11:47:35.000Z
Duration: 2 min 16 s
Channel: JoVE

K12 Standards

Florida Department of Education

High School

Life Science

SC.912.L.14

SC.912.L.14.5

comparing-mitochondrial-chloroplast-and-prokaryotic-genomes

Comparing Mitochondrial, Chloroplast, and Prokaryotic Genomes

Prymitywne komórki drapieżników zinternalizowały bakterie, które później przekształciły się w mitochondria, tworząc komórki eukariotyczne. Fotosyntetyczne cyjanobakterie również utworzyły symbiotyczne relacje z niektórymi z tych komórek eukariotycznych i ostatecznie przekształciły się w chloroplast.
Dzisiejsze genomy mitochondrialne i chloroplastowe są pozostałościami tych przodków genomów prokariotycznych.
W porównaniu z genomami mitochondrialnymi, genomy współczesnych prokariontów są duże, takie jak Escherichia coli, które zawierają około 5 milionów bps i prawie 5000 genów.
Ludzki genom mitochondrialny ma prawie 17 000 punktów bazowych długości i zawiera 37 genów - podczas gdy genom mitochondrialny Arabidopsis thaliana, rośliny kwitnącej, ma ponad 350 000 punktów bazowych, ale zawiera tylko 57 genów.
W porównaniu z obecnymi genomami sinic, takimi jak genom Synechocystis, który ma około 3,5 miliona punktów bazowych i zawiera około 3200 genów, genom chloroplastów wśród roślin lądowych ma do 200 000 punktów bazowych i zawiera 120-135 genów. 
Mimo że są znacznie mniejsze, zarówno genomy mitochondrialne, jak i chloroplastowe są pod kilkoma względami podobne do genomu prokariotycznego. Ich DNA nie wiąże się z białkami histonowymi i jest zwykle okrągłe i dwuniciowe, podobnie jak plazmidy bakteryjne. 
W porównaniu z genomem mitochondrialnym, genom chloroplastowy bardziej przypomina genom prokariotyczny. Zarówno genomy chloroplastów, jak i prokariotyczne mają dość podobne sekwencje DNA dla promotorów i terminatorów transkrypcji.
Ponadto genomy mitochondrialne zwierząt są na ogół mniejsze niż genomy mitochondrialne roślin, ponieważ zarówno genomy mitochondrialne chloroplastów, jak i roślin mają introny, których nie ma w większości genomów mitochondrialnych zwierząt.

<ol>
	<li>Smitha, Davida Roya i Patricka J. Keelinga. "Architektura genomu mitochondrialnego i plastydowego: powtarzające się tematy, ale znaczące różnice na krańcach". Proceedings of the National Academy of Sciences 112, nr 33 (2015): 10177-10184.</li>
	<li> Shah, VC. "Ewolucja genomu chloroplastowego." Proc. Indian natn. Sci. Acad. B49 N0 6 (1983): 636-646.</li>
</ol>

porównanie genomów mitochondrialnych, chloroplastowych i prokariotycznych

Współczesne genomy mitochondriów i chloroplastów zachowały niektóre cechy swoich przodków prokariotów, a także nabyły nowe cechy podczas ewolucji w komórkach eukariotycznych. Podobnie jak genomy prokariotyczne, genomy mitochondriów i chloroplastów nie wiążą się z białkami histonopodobnymi ani nie wykazują złożonego upakowania w struktury podobne do chromosomów, jak zaobserwowano u eukariontów. W przeciwieństwie do podziałów komórek mitotycznych obserwowanych w komórkach eukariotycznych, mitochondria i chloroplasty ulegają rozszczepieniu binarnemu i w równym stopniu rozdzielają swoje DNA na organelle potomne, jak to obserwuje się u prokariotów. Ponadto rybosomy zarówno w mitochondriach, jak i chloroplastach są wrażliwe na antybiotyki antybakteryjne. Genomy prokariotyczne mają miliony par zasad i tysiące genów; genomy mitochondriów i chloroplastów, z wyjątkiem kilku roślin, są znacznie mniejsze i zawierają tysiące par zasad z kilkoma setkami genów. Ta różnica w wielkości genomu wystąpiła, ponieważ podczas ewolucji znaczne części prymitywnych genomów mitochondrialnych i chloroplastowych zostały wyeksportowane do jądra. Ten eksport genów uzależnił je od genomu jądrowego w zakresie dostaw niektórych białek niezbędnych do ich biogenezy. Ścieżki ewolucyjne zwierząt i roślin spowodowały duże różnice między genomami mitochondriów zwierzęcych a mitochondriami i chloroplastami roślinnymi. Genomy mitochondrialne zwierząt są mniejsze niż genomy mitochondrialne i chloroplastowe roślin. Ponadto, podobnie jak większość genomów prokariotycznych, genomy mitochondrialne zwierząt nie niosą żadnych intronów. Jednakże introny są obecne w genomach zarówno mitochondriów roślinnych, jak i chloroplastów. W porównaniu z genomami mitochondrialnymi, genomy chloroplastów wykazują mniejsze zróżnicowanie pod względem wielkości i struktury, a także zawierają więcej genów. Na przykład liczba genów obecnych w genomie chloroplastowym Arabidopsis thaliana jest prawie dwukrotnie większa niż liczba genów obecnych w jego genomie mitochondrialnym. Co więcej, genomy chloroplastów są bardziej podobne do swoich prokariotycznych odpowiedników niż genom mitochondrialny, ponieważ są podobne pod względem sekwencji regulacyjnych i rozmieszczenia wielu klastrów genów.

Porównanie genomów mitochondrialnych, chloroplastowych i prokariotycznych

Dzisiejsze genomy mitochondrialne i chloroplastowe zachowały niektóre cechy swoich przodków prokariotów, a także uzyskały nowe ...

Education

JoVE Core

Molecular Biology

Biologia molekularna

Unit 1

Jednostka 1

DNA Replication

Replikacja DNA

KEY TERMS AND CONCEPTS

Kluczowe terminy i pojęcia

how organelle genomes resemble bacteria

Mitochondrial and chloroplast genomes still keep several traits from their bacterial ancestors. They also show changes that happened after these organelles evolved inside eukaryotic cells. Eukaryotic cells are cells with a nucleus, while prokaryotes are cells without one.

Like prokaryotic genomes, mitochondrial and chloroplast genomes do not bind with histone-like proteins. They also do not show the complex chromosome-like packaging seen in eukaryotes. Mitochondria and chloroplasts divide by binary fission, and they split their DNA equally into daughter organelles, just as prokaryotes do. Their ribosomes are also sensitive to antibacterial antibiotics.

These organelle genomes are much smaller than prokaryotic genomes in most cases. Prokaryotic genomes often contain millions of base pairs and thousands of genes. Mitochondrial and chloroplast genomes usually contain only thousands of base pairs and a few hundred genes, except in a few plants. This size difference happened because many genes from early mitochondrial and chloroplast genomes moved to the nucleus during evolution.

That gene transfer made mitochondria and chloroplasts depend on the nuclear genome for some of the proteins they need to build and function. Evolution in animals and plants also produced important differences among their genomes. Animal mitochondrial genomes are smaller than plant mitochondrial and chloroplast genomes, and they usually do not contain introns, which are noncoding sections within genes. In contrast, introns are present in both plant mitochondria and chloroplasts.

Chloroplast genomes are usually more stable in size and structure than mitochondrial genomes. They also contain more genes. In Arabidopsis thaliana, the chloroplast genome has almost twice as many genes as the mitochondrial genome. Chloroplast genomes are also closer to prokaryotic genomes because their regulatory sequences and many gene clusters are arranged in similar ways.

How Organelle Genomes Resemble Bacteria

replication in prokaryotes

Prokaryotic DNA Replication Steps

Prokaryotic DNA replication copies the chromosome before a cell divides. In bacteria, this process starts at a specific DNA site called the origin of replication. From there, the cell builds new DNA strands using enzymes that match each base with its partner. The DNA double helix first opens so replication can begin. As the strands separate, each original strand serves as a template. New nucleotides are added in a set order, which helps the cell make an accurate copy of its genetic material. <br...

replication in eukaryotes

Eukaryotic DNA Replication Steps

Eukaryotic DNA replication copies the genome before a cell divides. In eukaryotes, this process happens in a controlled sequence so each new cell can receive genetic information. Replication begins at specific sites on the DNA called origins. The DNA is opened, and each original strand serves as a template, meaning it guides the building of a new complementary strand. This sets up two DNA molecules from one original molecule. The process then continues as enzymes add matching nucleotides to...

dna base pairing

DNA Base Pair Rules

DNA base pairing follows specific rules that help DNA carry genetic information. In DNA, the bases pair in a regular way, with adenine matching thymine and cytosine matching guanine. These pairs fit together because of their chemical shapes and bonding patterns. These base pairs also support accurate DNA replication. When DNA copies itself, each strand can guide the formation of a new partner strand using the pairing rules. Understanding base pairing helps explain how DNA stays organized and...

the dna replication fork

DNA Replication Stress and Fork Stalling

DNA replication stress and fork stalling can disrupt the copying of a cell’s genome. The replication fork is the Y-shaped site where DNA strands separate and new complementary strands are made at the same time. This linked unwinding and synthesis helps cells duplicate DNA efficiently and with fewer errors. In organisms with small circular DNA, such as E. coli, replication often begins at a single origin. That setup creates two replication forks that move in opposite directions from the opening...

proofreading

Proofreading in DNA Replication

Proofreading in DNA replication helps keep DNA copying accurate. It is a built-in check that reduces mistakes as new DNA is made. DNA polymerase is the enzyme that carries out this checking during replication. When it adds a wrong nucleotide, it can remove the error and replace it with the correct one. This correction step helps maintain the correct DNA sequence. Proofreading is an important part of DNA replication because it supports genetic accuracy. By catching mistakes as they happen, the...

dna helicases

Helicase Motor Proteins in DNA Unwinding

Helicase motor proteins help unwind DNA during key cell processes. They use energy from ATP hydrolysis, which is the breakdown of ATP to release usable energy. This movement lets helicases separate DNA strands when the cell needs access to the genetic code. These enzymes are involved in DNA replication, repair, recombination, and transcription. Helicases are found in all living organisms, but their structure, function, and movement can differ. In prokaryotes, the DnaB helicase moves along the...

the replisome

DNA Replication Teams in the Replisome

DNA replication depends on the replisome, a coordinated complex of proteins that copies DNA with high accuracy. This DNA replication machinery brings many parts together so the leading and lagging strands can be made at the same time. A key idea in this process is the trombone model, proposed by Bruce Alberts in 1980. In this model, a loop forms on the lagging strand when a primer is made. The loop grows as an Okazaki fragment is synthesized, then falls apart when that fragment is finished.

lagging strand synthesis

Okazaki Fragments in DNA Replication

DNA replication uses a leading strand and a lagging strand, and they are made at different rates. The leading strand starts first. The lagging strand starts later, moves more slowly, and is made in pieces. The two strands also differ in direction and starting steps. Leading strand synthesis follows the opening replication fork. Lagging strand synthesis goes in the opposite direction. The leading strand needs one RNA primer, while the lagging strand needs multiple RNA primers. After priming,...

mismatch repair

Fixing DNA Copying Errors

Mismatch repair helps fix DNA copying errors after replication. When DNA is copied, small mistakes can slip through. This repair system finds those mismatches and corrects them before they become permanent changes. The process depends on a group of mutator proteins. These proteins work together to detect the error, remove the incorrect section, and help replace it with the proper DNA sequence. In this way, mismatch repair supports the accuracy of genetic information. If the repair system does...

dna topoisomerases

How Topoisomerases Untwist DNA

DNA topoisomerases are enzymes that untwist DNA when it becomes overcoiled during cell processes such as DNA replication and transcription. They help regulate positive and negative DNA supercoiling without changing the nucleotide sequence. Clockwise overwinding creates positively supercoiled DNA, while counterclockwise underwinding produces negatively supercoiled DNA. Topoisomerases are grouped into two main types. Type I topoisomerases act on one strand of double-stranded DNA, and they...

telomeres and telomerase

How Telomerase Protects Chromosome Ends

Telomerase helps protect chromosome ends during eukaryotic DNA replication. When the final primer is removed, a single-stranded DNA fragment can remain at the end of the chromosome. That piece cannot be copied in the same way as the rest of the strand because there is no 3' end for new DNA to attach to. If this end piece is not replaced, chromosomal DNA is gradually lost each time a cell divides. The exposed single-stranded DNA can also trigger a DNA damage response from enzymes that detect it.

non-nuclear inheritance

Cytoplasmic Inheritance in Cells

Cytoplasmic inheritance explains how some traits are passed through cell structures outside the nucleus. These traits come from organelles such as mitochondria and chloroplasts. They do not follow the usual nuclear pattern of inheritance. Mitochondria and chloroplasts each contain their own DNA. Because of this, they can carry genetic information that affects cell function and certain visible traits. In high school biology, this topic helps explain why not all inherited traits come from...

animal mitochondrial genetics

Animal Mitochondrial DNA and Inheritance

Animal mitochondrial DNA has its own genome, separate from nuclear DNA. It is a double-stranded, closed circular molecule with about 20,000 base pairs. One strand is the heavy, or H-strand, because it is rich in guanine. The other is the light, or L-strand, because it is rich in cytosine. Compared with nuclear DNA, mitochondrial DNA has very little non-coding sequence. It also has no introns. Its genes are packed closely together, and some even overlap. The D-loop is the main non-coding...

comparing mitochondrial, chloroplast, and prokaryotic genomes

Mitochondrial and chloroplast genomes still keep several traits from their bacterial ancestors. They also show changes that happened after these organelles evolved inside eukaryotic cells. Eukaryotic cells are cells with a nucleus, while prokaryotes are cells without one. Like prokaryotic genomes, mitochondrial and chloroplast genomes do not bind with histone-like proteins. They also do not show the complex chromosome-like packaging seen in eukaryotes. Mitochondria and chloroplasts divide by...

export of mitochondrial and chloroplast genes

export-of-mitochondrial-and-chloroplast-genes

How Organelles Pass Genes to the Nucleus

Eukaryotic cells can carry three genetic systems: nuclear, mitochondrial, and chloroplast. Over time, many genes from mitochondria and chloroplasts have moved into the nucleus. In some plant species, this gene transfer is still happening. This movement has affected large parts of the genome in some organisms. About 18% of the Arabidopsis thaliana nuclear genome is thought to come from the chloroplast's cyanobacterial ancestor. In yeast, around 75% of the genome is derived from the...

single-strand dna binding proteins

How SSB Proteins Protect DNA Strands

Single-strand DNA-binding proteins, or SSB proteins, help protect DNA during replication. When double-stranded DNA is unwound, the two strands separate. SSB proteins bind to the exposed single strands and keep them stable. These proteins bind in a sequence-independent manner. That means the order of the nitrogenous bases does not have to follow a specific pattern for SSB proteins to attach. Their binding straightens single-stranded DNA and makes it more rigid. This support may help DNA...

key terms and concepts

See how mitochondrial and chloroplast genomes keep bacterial traits, why their DNA is smaller, and how plant and animal organelles differ.

How Organelle Genomes Resemble Bacteria | JoVE K12

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Biology

BIO.5

BIO.5.B

What are Cells?

Cells are the smallest and basic units of life, whether it is a single cell that forms the entire organism, e.g., in a bacterium or trillions of them, ...

Characteristics of Life

Biology is a natural science that studies life and living organisms, including their structure, function, development, interactions, evolution, ...

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Animal and Plant Cell Structure

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Eukaryotic Evolution

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Cell Diversity

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Chemistry of the Cell

The cell is chemically composed of water, organic molecules and inorganic ions.
Water
The polarity of the water molecule and its resulting hydrogen ...

Describe the scientific theory of cells (cell theory) and relate the history of its discovery to the process of science.

SC.912.L.14.1

Cell Size

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Eukaryotic Compartmentalization

One of the distinguishing features of eukaryotic cells is that they contain membrane-bound organelles, such as the nucleus and mitochondria, that carry ...

Prokaryotic Cells

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Cytoplasm

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The Nucleus

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Endoplasmic Reticulum

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Ribosomes

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Golgi Apparatus

As they leave the Endoplasmic Reticulum (ER), properly folded and assembled proteins are selectively packaged into vesicles. These vesicles are ...

Microtubules

There are three types of cytoskeletal structures in eukaryotic cells&#x2014;microfilaments, intermediate filaments, and microtubules. With a diameter of ...

Peroxisomes

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Gap Junctions

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The Extracellular Matrix

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Tissues

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Plant Cell Wall

The plant cell wall gives plant cells shape, support, and protection. As a cell matures, its cell wall specializes according to the cell type. For ...

Plasmodesmata

The organs in a multicellular organism&#x2019;s body are made up of tissues formed by cells. To work together cohesively, cells must communicate. One way ...

What are Membranes?

A key characteristic of life is the ability to separate the external environment from the internal space. To do this, cells have evolved semi-permeable ...

Membrane Fluidity

Cell membranes are composed of phospholipids, proteins, and carbohydrates loosely attached to one another through chemical interactions. Molecules are ...

Fluid Mosaic Model

The fluid mosaic model was first proposed as a visual representation of research observations. The model comprises the composition and dynamics of ...

What is an Electrochemical Gradient?

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Diffusion

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Osmosis

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Tonicity in Animals

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Tonicity in Plants

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Introduction to Membrane Proteins

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Facilitated Transport

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Primary Active Transport

In contrast to passive transport, active transport involves a substance being moved through membranes in a direction against its concentration or ...

Secondary Active Transport

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Receptor-mediated Endocytosis

Overview

Receptor-mediated endocytosis is a process through which bulk amounts of specific molecules can be imported into a cell after binding to cell ...

Pinocytosis

Cells use energy-requiring bulk transport mechanisms to transfer large particles, or large amounts of small particles, into or out of the cell. The cells ...

Phagocytosis

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Exocytosis

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Relate structure to function for the components of plant and animal cells. Explain the role of cell membranes as a highly selective barrier (passive and active transport).

SC.912.L.14.2

Cell Structure

Background
Cells represent the most basic biological units of all organisms, whether it be simple, single-celled organisms like bacteria, or large, ...

Compare and contrast the general structures of plant and animal cells. Compare and contrast the general structures of prokaryotic and eukaryotic cells.

SC.912.L.14.3

Overview of Microscopy Techniques

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Introduction to Light Microscopy

The light microscope is an instrument used by researchers in many different fields to magnify specimens to as much as a thousand times their original ...

Overview of Electron Microscopy

The wavelengths of visible light ultimately limit the maximum theoretical resolution of images created by light microscopes. Most light microscopes can ...

phase-contrast-and-differential-interference-contrast-microscopy

Phase Contrast and Differential Interference Contrast Microscopy

Phase-Contrast Microscopes
In-phase-contrast microscopes, interference between light directly passing through a cell and light refracted by cellular ...

Confocal Fluorescence Microscopy

Confocal microscopy is an advanced microscopic technique. The prime advantage of the confocal microscope over other microscopy techniques is its ability ...

Introduction to Fluorescence Microscopy

Fluorescence microscopy is a very powerful analytical tool that combines the magnifying properties of light microscopy with visualization of fluorescence. ...

Super-resolution Fluorescence Microscopy

Super-resolution fluorescence microscopy (SRFM) provides a better resolution than conventional fluorescence microscopy by reducing the point spread ...

Compare and contrast structure and function of various types of microscopes.

SC.912.L.14.4

The present-day mitochondrial and chloroplast genomes have retained some of the characteristics of their ancestral prokaryotes and also have acquired new ...

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

The Tree of Life - Bacteria, Archaea, Eukaryotes

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The Anatomy of Chloroplasts

Green algae and plants, including green stems and unripe fruit, harbor specialized organelles called chloroplasts to carry out photosynthesis. They ...

Explain the evidence supporting the scientific theory of the origin of eukaryotic cells (endosymbiosis).

An Overview of Genetics and Disease

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Factors Affecting Illness

When a person&#39;s physical, emotional, intellectual, social development or spiritual functioning is compromised, this deviation from a healthy normal ...

Gene-Environment Interactions

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Dimensions of Health and Illness

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Factors Affecting the Risk of Infection

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SC.912.L.14.6

A. Cells have characteristic structures and functions that make them distinctive.

B. Processes in a cell can be classified broadly as growth, maintenance, reproduction, and homeostasis.

C. Life can be organized in a functional and structural hierarchy ranging from cells to the biosphere.

D. Most multicellular organisms are composed of organ systems whose structures reflect their particular function.

How Organelle Genomes Resemble Bacteria

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