Name: cytoplasmic inheritance in cells
Uploaded: 2020-11-23T11:47:35.000Z
Duration: 1 min 29 s
Channel: JoVE

K12 Standards

Alabama Course of Study Science

9-12

Biology

from-molecules-to-organisms-structures-and-processes

From Molecules to Organisms: Structures and Processes

9-12.B.1.3

Non-nuclear Inheritance

- Nelle cellule eucariotiche,
mitocondri e plastidi,

una categoria di organelli
di cellule vegetali

che comprende i cloroplasti,

si riproducono
indipendentemente nel citoplasma

e ognuno di essi ha il proprio set di geni

che ne dirige la
riproduzione e la funzione.

Il DNA mitocondriale e
plastidico assume la forma

di piccole molecole circolari di DNA

e viene chiamato DNA non
nucleare o citoplasmatico.

Ogni organello trasporta molte
copie identiche del suo DNA,

in contrasto con il nucleo,
dove in genere ci sono

solo due copie di ciascun cromosoma.

Inoltre, durante la divisione
cellulare, gli organelli

vengono casualmente separati
in nuove cellule figlie,

quindi il DNA non nucleare
che viene trasmesso

non segue uno schema prestabilito.

Nella riproduzione
animale e di molte piante,

il citoplasma nello
zigote proviene dall'uovo.

Perciò, mentre entrambi i
genitori contribuiscono equamente

al DNA nucleare, il DNA non
nucleare viene trasmesso

solo dalla madre.

Ciò significa che alcuni tratti,
come i disturbi metabolici

derivanti da mutazioni nei mitocondri,

possono essere rintracciati
in modo matrilineare.

Inoltre, alcuni tratti
fisici delle piante, come

il colore delle foglie, sono
diretti da geni non nucleari

e vengono tramandati uniparentalmente.

Miko, I. "Geni non nucleari e loro eredità". Educazione alla natura 1, n. 1 (2008). [<a href="https://www.nature.com/scitable/topicpage/non-nuclear-genes-and-their-inheritance-589">Fonte</a>]

Patananan, Alexander N., Ting-Hsiang Wu, Pei-Yu Chiou e Michael A. Teitell. 2016. "Modifica del genoma mitocondriale". Metabolismo cellulare 23 (5): 785–96. [<a href="https://doi.org/10.1016/j.cmet.2016.04.004">Sorgente</a>]

eredità non-nucleare

La maggior parte del DNA risiede nel nucleo di una cellula. Tuttavia, alcuni organelli del citoplasma cellulare, come i cloroplasti e i mitocondri, hanno anche il loro DNA. Questi organelli replicano il loro DNA indipendentemente dal DNA nucleare della cellula in cui risiedono. L'eredità non nucleare descrive l'eredità di geni provenienti da strutture diverse dal nucleo.

I mitocondri sono presenti sia nelle piante che nelle cellule animali. Sono considerate come le "centrali elettriche" delle cellule eucariotiche perché rompono il glucosio per formare energia che alimenta l'attività cellulare. Il DNA mitocondriale è costituito da circa 37 geni, e molti di loro contribuiscono a questo processo, chiamato fosforilazione ossidativa.

I cloroplasti si trovano nelle piante e nelle alghe e sono i siti di fotosintesi. La fotosintesi permette a questi organismi di produrre glucosio dalla luce solare. Il DNA cloroplasto è costituito da circa 100 geni, molti dei quali sono coinvolti nella fotosintesi.

A differenza del DNA cromosomico nel nucleo, il cloroplasto e il DNA mitocondriale non rispettano l'ipotesi mendeliana che metà materiale genetico di un organismo provenga da ciascun genitore. Questo perché gli spermatozoi generalmente non contribuiscono al DNA mitocondriale o cloroplasto agli zigoti durante la fecondazione.

Mentre uno spermatozoi contribuisce principalmente a un insieme aploide di cromosomi nucleari allo zigote, una cellula uovo contribuisce con i suoi organelli oltre ai suoi cromosomi nucleari. Gli zigoti (e i cloroplasti nelle cellule vegetali) ricevono tipicamente mitocondri e cloroplasti esclusivamente dalla cellula uovo; questa è chiamata eredità materna. L'eredità materna è un tipo di eredità non nucleare, o extranucleare.

Perché i mitocondri e i cloroplasti hanno il loro DNA? La spiegazione prevalente è la teoria endosimbiotica. La teoria endosimbiotica afferma che i mitocondri e i cloroplasti erano un tempo procarioti indipendenti. Ad un certo punto, si unirono alle cellule eucariotiche ospiti ed entrarono in una relazione simbiotica, che avvantaggiò entrambe le parti.

Eredità non-nucleare

Most DNA resides in the nucleus of a cell. However, some organelles in the cell cytoplasm&#8288;&#8212;such as chloroplasts and ...

Education

Didattica

JoVE Core

Molecular Biology

Biologia Molecolare

Unit 1

Unità 1

DNA Replication

Replicazione del DNA

KEY TERMS AND CONCEPTS

TERMINI E CONCETTI CHIAVE

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 chromosomes in the nucleus.

Cytoplasmic inheritance is often linked to the mother because the egg cell provides most of the cytoplasm to the embryo. That is why some traits appear to pass through the maternal line. Understanding this pattern is important for studying organelle genetics and unusual inheritance patterns.

Cytoplasmic Inheritance in Cells

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 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

comparing-mitochondrial-chloroplast-and-prokaryotic-genomes

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...

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

Learn how mitochondria and chloroplasts pass traits outside the nucleus through cytoplasmic inheritance, a key pattern in high school biology.

Cytoplasmic Inheritance in Cells | JoVE K12

molecular biology

Le video animazioni di JoVE Core Molecular Biology, organizzate in video lezioni, illustrano i processi molecolari cellulari in maniera chiara e concisa. Inoltre, nei video di "scienziati in azione", i concetti scientifici vengono applicati e dimostrati da ricercatori attraverso esperimenti in laboratorio.

myJoVE Corporation

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Nonsense-mediated mRNA Decay

The Eukaryotic Promoter Region

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Co-activators and Co-repressors

The Proteasome

Master Transcription Regulators

Regulated Protein Degradation

Regulated mRNA Transport

Proteins: From Genes to Degradation

mRNA Stability and Gene Expression

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9-12.B.1.2

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9-12.B.1.2.a

Cytoplasmic Inheritance in Cells

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