Categorie: Tutti - ribosomes - transcription - dna - nucleus

da Anni Yang mancano 10 anni

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Prokaryotes vs. Eukaryotes

Eukaryotic cells are characterized by their distinct nucleus enclosed by a nuclear envelope, complex gene expression mechanisms including RNA processing, and transcription involving three types of RNA polymerases and various transcription factors.

Prokaryotes vs. Eukaryotes

Prokaryotes vs. Eukaryotes

Prokaryotes

Binary fission

chromosome is duplicated before division

2 cells with identical genetic composition

50 kinds of protein
composed of 3 kinds of rRNA
smaller size
Circular and has no ends

not formed into chromosomes

Plasmids

only one circular DNA molecule

"naked" and has no histones

Located in the cytoplasm

no cytoplasmic streaming

no cytoskeleton

consist of 2 protein building blocks
not complex

Proton driven

Rotary movement

doesn't have RNA processing

sigma factors are needed to start

needs a DNA sequence called pribnow box to start

Carried out by a single RNA polymerase

No membrane bound organelles
No true nucleus
0.2-2.0 mm in diameter

Eukaryotes

Cell division
Mitosis

movements directed by microtubules

each daughter cell receives copy of original DNA

replicated chromosomes positioned in middle of cytoplasm then segregated

Use special enzyme called telomerase

Ribosomes
80 kinds of protein
composed of 5 kinds of rRNA
larger size
DNA
Linear

Organized into chromosomes

contains a number of chromosomes

Complexed with "histones"

Located in the nucleus
Flagella
consist of multiple microtubules
Complex

ATP driven

Bending movement

Gene expression
undergoes RNA processing

spliceosome catalyzes the reaction

takes out the introns and keeps exons

Transcription

transcription factors needed to initiate process

needs DNA sequence called the promoter to start

carried out by 3 types of RNA polymerases

Nucleus
Covered by nuclear envelope
Has distinct nucleus
Size of cell
10-100mm in diameter