Why is it argued that paleakyotes should be isolated from prokaryotes?

Archaea or archaea are some bacteria that grow in extremely special environments, and they used to be classified because archaea, also known as archaea or archaea, are a group of organisms that are independent of eubacteria and eukaryotes very early in the evolutionary pathway, mainly including some unique ecological types of prokaryotes, which are significantly different from eukaryotes and eubacteria in terms of biochemistry and macromolecular structure In terms of cell structure, it is relatively close to eubacteria, and its morphological structure, The DNA structure and its basic life activities are similar to those of prokaryotic cells, and they are both prokaryotic organisms Therefore, the answer is:

Because palakaryotes have characteristics that are different from both prokaryotic and eukaryotic cells, such as: lipids in cell membranes are not saponifiable; The cell wall does not contain peptidoglycan, some are protein-based, some contain heteropolysaccharides, and some are similar to peptidoglycan, but none of them contain muramic acid, D-type amino acids, and diaminopinoheptanedic acid.

It has been suggested that bacteria, archaea, and eukaryotes may each represent the descendants of a group of distant ancestors with simple genetic mechanisms. The phylogenetic tree based on RNA sequences also shows three distinct clades: bacteria, archaea and eukaryotes.

Therefore, it is advocated to separate the paleokaryotes.

Differences:

Eukaryotary transcription takes place in the nucleus, whereas prokaryotes do not have a nucleus and take place in the nucleomimetry; Eukaryotes generally code for only one gene, the monocistron, while prokaryotic transcription is usually polycistron; Eukaryotary RNA enzymes rely on transcription factors to recognize and bind to the starting sequence.

However, the prokaryotic holoenzyme binding promoter region reaches the transcription start site, and after the first phosphodiester bond is generated, the 6 subunits are detached, marking the completion of initiation. Eukaryotes have three different RNA polymerases that catalyze RNA synthesis and cannot transcribe RNA independently, and all three polymerases must be assisted by protein transcription factors to transcribe RNA.

Prokaryotes have only one RNA polymerase that catalyzes the synthesis of all RNA and can directly initiate transcription to synthesize RNA.

Eukaryotic transcription and translation cannot occur at the same time, whereas prokaryotes can; Mature RNA in eukaryotes needs to undergo processing processes such as modification, shearing, etc., while prokaryotes do not.

Archaea, sometimes called "archayotes," were recognized as prokaryotes before 1970 AD because, like bacteria, archaea do not have a nucleus and no membranous organelles. Referring to archaea as "archaea" is a way of referring to bacteria as "eubacteria" and grouping them together as prokaryotes — a classification that has long since become outdated, but you still see it a lot on the Internet, because that's what many readers receive about their biological education.

In the seventies and eighties of the twentieth century, studies successively found that there were repetitive sequences and nucleosomes in the genome of archaea [1], and at that time, there were voices of changing the classification scheme to isolate them. Half a century ago, people thought that archaea mainly lived in extreme environments such as volcanic hot springs and salt lakes, but later it was discovered that they were actually rotten streets, from soil, oceans, rivers to human mouths, large intestines, and **, everywhere.

Recent decades of research have shown that archaea have their own unique evolutionary process and are significantly different from bacteria, so the three-domain system proposed in 1977 lists archaea, bacteria, and eukaryotes as one domain

The classification and mapping methods of the various realms, phylums, classes, and purposes have changed many times since then.

You can also find such a phylogenetic tree:

Similarities between archaea and bacteria:

The cell volume is much smaller than that of eukaryotic cells, there is no nucleus, there are no membrane-bound organelles, a circular genome and manipulation groups (operons) are used, most genes have no introns, no post-transcriptional modifications, and polycistronic mRNA is used, and there are no 5'End caps[2], ribosomes are all 70 s in size (80 s for eukaryotes). There are many plasmids.

Similarities between archaea and eukaryotes:

There are no peptidoglycans outside the cell membrane, no muramic acid in the cell wall, DNA binds to histones, translation begins with methionine, uses similar RNA polymerases, promoters, and other transcriptional mechanisms, uses similar DNA replication and repair systems, and uses Type V ATPase. Ribosomes are sensitive to ubiquitin.

Unique features of archaea:

Unlike other organisms, the cell wall structure, flagellin structure, ribosome structure, tRNA sequence, and metabolism are glycerol ethers rather than glycerides, and there is no fatty acid synthase.

The answer to this is **.

Common features of DNA replication in prokaryotes and eukaryotes:

1. It is divided into three processes: initiation, extension and termination;

2 Must have primers that provide the 3' hydroxyl terminus;

The three parental DNA molecules were used as templates, four deoxytriphosphate nucleosides (DNTPs) were used as substrates, and a variety of enzymes and proteins were used.

DNA topoisomerase, DNA chain enzyme, single-stranded binding protein, primase,

DNA polymerases, RNA enzymes, and DNA ligases.

4. Generally, it is bidirectional replication, semi-reserved replication, and semi-discontinuous replication.

Prokaryotes differ from eukaryotes DNA replication characteristics:

1 Eukaryotes are linear DNA, with multiple replication start sites, forming multiple replication forks, and DNA polymerases move more slowly than prokaryotes. Prokaryotes are generally circular DNA with a single replication start site.

2 Eukaryotic DNA replication occurs only in the S phase of the cell cycle, and replication is no longer carried out after the start of a replication before completion, and multiple replication in prokaryotes occurs at the same time.

3 Eukaryotes replicon vary in size and are not synchronized.

4Prokaryotes have replication start sites composed of 9-mer and 13-mer repeats, while eukaryotes have no fixed replication start sites.

5 Eukaryotes have five DNA polymerases that require mg+The primary replicase is DNA polymerase δ ( primers are synthesized by DNA polymerase. There are only three types of prokaryotes, and the main replicase enzyme is DNA polymerase III

6 The eukaryotic ends are complemented by telomerase, while the prokaryotes are complemented in the form of polycouplets.

7 RNA primers between eukaryotic Okazaki fragments are removed by exonuclease MF1, while prokaryotic Okazaki fragments are removed by DNA polymerase I. 8 eukaryotic DNA polymerase is responsible for mitochondrial DNA synthesis. 9. The high ability of eukaryotic DNA polymerase δ comes from the interaction between RF-C protein and PCNA protein.

The ability of prokaryotic DNA polymerase III to advance comes from the interaction with the complex (clamp loader) with the subunit dimer (clamp).

Difference Between Prokaryotic and Eukaryotic DNA Replication:

1. The DNA replication of eukaryotes has multiple replication start sites, while prokaryotes have only one start site.

2. Once eukaryotic replication is initiated, no new replication can be started before the replication is completed, and the prokaryotic replication start site can start new replication continuously, especially in rapidly reproducing cells.

3. Eukaryotes and prokaryotes have different replication regulation.

4. The DNA polymerase III of the prokaryotes forms a dimer complex when replicating, while the eukaryotic polymerase remains separated.

5. The polymerase of eukaryotes does not have 5'-3'Exonuclease activity, which requires excision of a protein called FEN15'End primers, prokaryotic DNA polymerase I have 5'-3'Exonuclease activity.

Answer: e

The average slag in the synthesis direction is 5"→3"。Prokaryotic primers are 10-10 nucleotides in length; The Okazaki fragment is 1000 2000 nucleotides; 1 replication starting point. The length of eukaryotic primers is unclear; The Okazaki fragment is hundreds of nucleotides; There are multiple replication starting points.