What are some differences between transcription and DNA replication?
Similarities:Both follow the direction from 5’ to 3’ (actually any polymerases, including RdRp and reverse transcriptase follow this rule).Both use nucleoside triphosphate (NTP or dNTP) as substrates, which lose a diphosphate group upon ligation to the nascent strand (which again is true for all polymerases).Differences:RNA transcription is de novo (primer independent), while DNA replication is primer dependent. One consequence is that there is a free triphosphate moiety at the 5’ end of the nascent RNA, because the first NTP being incorporated has nothing to ligate to. This moiety is later used to make the triphosphate bridge of the 5’ cap of mRNA.Another is that during RNA transcription, only a small segment of the parental DNA serves as the template. While OTOH, DNA replication goes through the entire DNA strand. It makes sense because RNA transcription is used to express a specific gene, while DNA replication is used to replicate the entire genome.Several viruses can integrate into the host chromosome as a piece of proviral DNA. Examples include retroviruses infecting eukaryotes and some DNA viruses infecting bacteria (also known as lysogenic bacteriophages). One interesting consequence is that because the genetic material of lysogenic phages is DNA, which is replicated via DNA replication, the proviral DNA needs to be excised before replication commences. While OTOH, because the genetic material of retroviruses is RNA, which is produced by RNA transcription, the proviral DNA of retroviruses doesn’t need to come off, and remains indefinitely in the host chromosome.
If transcription could proceed in both directions along both DNA strands of a gene....?
2 http://www.bookrags.com/research/one-gen...
How is information in a gene transcribed into the RNA?
The process of transcription is defined to be undergone with the help of an enzyme ,DNA dependent RNA polymerase in both the eukaryotes and prokaryotes.In prokaryotes, sigma factor and rho factor are the intiating and terminating factor respectively and they get bound to the polymerase at the promoter and terminator. RNA polymerase alone acts for elongation process. It works in the polarity of 5′ to 3′ and therefore the DNA strand running from 3′ to 5′ end acts as template strand and the other strand as coding strand.When the RNA polymerase reaches the terminator of the transcription unit , the rna polymerase and the nascent RNA falls off.In eukaryotes, RNA polymerase 1, 2, and 3 are responsible for several transcriptions. Capping, and tailing is further accompanied by splicing of introns using splicosome.
What are the major differences between transcription and translation in DNA and RNA?
Transcription is the synthesis of RNA from a DNA template where the code in the DNA is converted into a complementary RNA code. Translation is the synthesis of a protein from an mRNA template where the code in the mRNA is converted into an amino acid sequence in a protein.Transcription:1. It is formation of RNA from DNA.2. The template is antisense strand of DNA.3. It occurs inside the nucleus in eukaryotes and cytoplasm in prokaryotes.4. The raw materials are four types of ribo-nucleoside triphosphates — ATP, GTP. CTP and UTP.5. It forms three types of RNAs — rRNA, tRNA and mRNA.6. Transcription requires RNA polymerases and some transcription factors.7. Polymerase moves over the template. 8. An adapter molecule is not required,9. Product often requires splicing.10. The product undergos processing that involves cutting, modification of nitrogen bases, folding and attaching of specific groups at the ends.Translation:1. It is synthesis of polypeptide over ribosome.2. The template is mRNA.3. It occurs in cytoplasm.4. The raw materials are 20 types of amino acids.5. All the three types of RNAs take part in translation.6. Translation requires initiation, elongation and translocase factors.7. Ribosome moves over mRNA.8. Adapter (= adaptor) molecules bring amino acids over the template.9. Splicing is absent.10. Processing involves occasional modification of amino acids, combining with other substances (e.g., glycosylation) and packing.just Go through it in a simple way
What are 3 different levels of gene regulation? and provide an example of a regulated trait in eukaryotes?
Regulated stages of gene expression Any step of gene expression may be modulated, from the DNA-RNA transcription step to post-translational modification of a protein. The following is a list of stages where gene expression is regulated, the most extensively utilised point is Transcription Initiation: Chromatin domains Transcription Post-transcriptional modification RNA transport Translation mRNA degradation http://en.wikipedia.org/wiki/Regulation_of_gene_expression http://en.wikipedia.org/wiki/Gene_expression#Regulation_of_gene_expression Eukaryotes need to regulate their genes for different reasons than prokaryotes. In prokaryotes, gene regulation allowed them to respond to their environment efficiently and economically. While eukaryotes can respond to their environment (we'll see an example of this later), the main reason higher eukaryotes need to regulate their genes is cell specialization. Whereas prokaryotes are (relatively speaking) simple, unicellular organisms, multicellular eukaryotes consist of hundreds of different cell types, each differentiated to serve a different specialized function. Each cell type differentiates by activating a different subset of genes. (For more on this, see the module on developmental genetics.) Because of the multitude of cell types, the regulation of gene expression required to bring about such differentiation is necessarily complex. One way this complexity is demonstrated is in multiple levels of regulation of gene expression.
What are 3 ways in which gene regulation differs between prokaryotic and eukaryotic cells?
Well there are more regulatory pathways in the eukaryotic systems than in the prokaryotic systems mainly because eukaryotes are multicellular. So the mRNA made could be 1. degraded if its faulty (many pathways of degradation) 2. By decreasing a factor needed for protein synthesis, the production of the protein product using mRNA could be stalled for a bit. So yeah there could be pathways for that. so there are many ways by which gene expression is regulated in eukaryotes such as I - Transcription Control The most common type of genetic regulation Turning on and off of mRNA formation II - Post-Transcriptional Control Regulation of the processing of a pre-mRNA into a mature mRNA III - Translational Control Regulation of the rate of Initiation VI - Post-Tranlational Control Regulation of the modification of an immature or inactive protein to form an active protein But main differences are 1. prokaryotes don't have a nucleus so the transcription and its regulation is much more simpler where eukaryotes have to transcribe and then have a process for mRNA processing (5'cap, splicing nd poly A tail additon) and then have a special mechanism to transport the pocessed mature mRNA to the cytoplasm from the nucleus. 2. Another big difference is the complexity. Eukaryotic system is wayy more complex. If you look at the beginning where I mentioned about the various regulatory steps involved in eukaryotic systems .... do not apply for prokaryotic systems as much. There are many factors involved with gene regulation that differ majorly amongst the two cell types too. 3. prokaryotes have operons (Genes are grouped together based on similar functions into functional units called operons). While eukaryotes do not contain operons. The eikaryotes have Transcription start site, basal promoter with a TATA binding site etc etc. 4. Prokaryotes don't contain introns. So splicing of introns and joining of exons as done in eukaryotes are not needed. 5. Eukaryotes don't express their genes all at once they express one at a time. Prokaryotes do. http://www.infoplease.com/cig/biology/re...
Why is DNA replicated in the 5'-3' direction?
why in 5′-3′ direction?the energy for the formation of the phosphodiester bond comes from the dNTP, which has to be added. dNTP is a nucleotide which has two additional phosphates attached to its 5' end. In order to join the 3'OH group with the phosphate of the next nucleotide, one oxygen has to be removed from this phosphate group. This oxygen is also attached to two extra phosphates, which are also attached to a Mg++. Mg++ pulls up the electrons of the oxygen, which weakens this bond and the so called nucleophilic attack of the oxygen from the 3'OH succeeds, thus forming the phospodiester bond.why cannot it take place in 3′-5′ direction?If you try to join the dNTP's 3'OH group to the 5' phosphate of the next nucleotide, there won't be enough energy to weaken the bond between the oxygen connected to the 5' phosphorous (the other two phosphates of the dNTP are on the 5' end, not on the 3' end), which makes the nucleophilic attack harder because there is no good leaving group to allow this to happen.
Plasmid gene orientation?
Firstly RNA polymerase reads the template strand in a 3'->5' Direction. Alternating transcription direction is because there is two strands. These plasmids are from bacteria not viruses so they don't need one continuous sense or antisense genomes, instead they have the sense and antisense strands interchanging depending on which transcription unit we are referring to. One operon may start with the sequence 3'-ATTATATAG-5' and RNA polymerase will come along and bind to this sequence specifically via its sigma subunit and start transcribing, now imagine it transcribed the same sequence into mRNA it would be 5'-UAAUAUAUC-3' - now the mRNA is always the sense and the strand that it was copied from is called the antisense. But imagine polymerase bound to the other strand which would be 5'-TAATATATC-3' this would mean that a different subunit could cause polymerase to recognise this sequence, this would mean that the mRNA will be transcribed as 3'-AUUAUAUAG-5' and this mRNA is always the sense and the sequence which is complementary to it is the antisense. So here you see that at one specific point in the plasmid polymerase can bind to either strand depending on things like sigma factors. This binding of polymerase to DNA will always orient polymerase so that it is reading in the 3'->5' direction, this means that the mRNA will always be transcribed in the 5'->3' direction. Here we see how we have transcribed two complementary sequences of DNA to produce two different mRNAs which are both sense and both strands are antisense - meaning that whether it is sense or antisense depends solely on the mRNA you get from it since it is always sense. So the ribosome will recognise the mRNA at the 5' and read along 5'->3' and produce a protein. That's about all I can say about that - 5' binds and is read along and produces an amino acid sequence dependent on its mRNA sequence. Using my example these two mRNAs will produce 2 different proteins even though the ribosome moved in two different directions - obviously at different times and locations along the plasmid in real life.