Biology- mRNA transcription help! Watch

ImagineCats
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I get in the nucleus theres the DNA and the RNA polymerase comes along, breaking the H bonds and separating the strands causing them to uncoil and then the free RNA nucleotides in the nucleus go ahead and pair up with the now alone bases in the DNA- but whats the point of the mRNA's nucleotides joining with the DNA nucleotide only to be a single strand again?

I'm stumped after the separation of the double helix tbh.

Looked on youtube but no luck- can someone explain to me what happens after this? Maybe in baby terms so I can get my head around it, then throw in the key words.

Thanks!
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ImagineCats
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cmon people
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crashMATHS
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(Original post by ImagineCats)
I get in the nucleus theres the DNA and the RNA polymerase comes along, breaking the H bonds and separating the strands causing them to uncoil and then the free RNA nucleotides in the nucleus go ahead and pair up with the now alone bases in the DNA- but whats the point of the mRNA's nucleotides joining with the DNA nucleotide only to be a single strand again?

I'm stumped after the separation of the double helix tbh.

Looked on youtube but no luck- can someone explain to me what happens after this? Maybe in baby terms so I can get my head around it, then throw in the key words.

Thanks!
Possibly, because it needs to be a single strand otherwise the ribosomes will not be able to read the code.

Also a single strand is likely to be easier to shuttle out of the nuclear pores.

I'm guessing it has to attach to the double helix first, so that enzymes can allow for a complementary strand to be formed. It they were just put together in any order, you might have a gene coding for glucagon end up producing insulin!
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Eloades11
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Moved to the biology forum where hopefully you'll get more responses
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User2334541
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(Original post by ImagineCats)
I get in the nucleus theres the DNA and the RNA polymerase comes along, breaking the H bonds and separating the strands causing them to uncoil and then the free RNA nucleotides in the nucleus go ahead and pair up with the now alone bases in the DNA- but whats the point of the mRNA's nucleotides joining with the DNA nucleotide only to be a single strand again?

I'm stumped after the separation of the double helix tbh.

Looked on youtube but no luck- can someone explain to me what happens after this? Maybe in baby terms so I can get my head around it, then throw in the key words.

Thanks!
The use of the RNA nucleotides joining on the DNA molecule is so that the mRNA molecule can transcribe the gene sequence for a specific protein, that is found in the specific region of the DNA molecule. The mRNA essentially can, after being spliced by removing all the introns, which are regions of non-functional codons that does not code for an amino acid, allows for the protein to be translated into the form of the protein required by the phospholipid-membrane bound cell, with the use of specific ribosomes to allow the tRNA molecule to attach to the codons, which were before relating back to transcription, were the regions of DNA that code for the amino acid, to form the protein. The anticodon loop, therefore becomes complementary to the mature mRNA codon, to allow the amino acids to form the peptide bond, with the use of an enzyme, to bind them together.

Further structure is developed for the protein, undergoing the secondary, tertiary and quaternary structures respectively.

If you have any questions, just send me a PM! I am happy to help!
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Carrot_Cake_13
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Just posting so I can have a read when I later revise this :lol:
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ImagineCats
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(Original post by Eloades11)
Moved to the biology forum where hopefully you'll get more responses
Thank you!
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ImagineCats
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(Original post by User2334541)
The use of the RNA nucleotides joining on the DNA molecule is so that the mRNA molecule can transcribe the gene sequence for a specific protein, that is found in the specific region of the DNA molecule. The mRNA essentially can, after being spliced by removing all the introns, which are regions of non-functional codons that does not code for an amino acid, allows for the protein to be translated into the form of the protein required by the phospholipid-membrane bound cell, with the use of specific ribosomes to allow the tRNA molecule to attach to the codons, which were before relating back to transcription, were the regions of DNA that code for the amino acid, to form the protein. The anticodon loop, therefore becomes complementary to the mature mRNA codon, to allow the amino acids to form the peptide bond, with the use of an enzyme, to bind them together.

Further structure is developed for the protein, undergoing the secondary, tertiary and quaternary structures respectively.

If you have any questions, just send me a PM! I am happy to help!
I understand the translation part- I'm just still confused about why go through with the complimentary base pairing of the floating free nucleotides only to be split again to be a single strand?? How does it even go back to the strand? Thank you for your help so far!
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Asklepios
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(Original post by ImagineCats)
whats the point of the mRNA's nucleotides joining with the DNA nucleotide only to be a single strand again?
The free ribonucleotides needs to match up with the DNA strand (through Watson-Crick base pairing) in order for the mRNA strand to be synthesized as the right 'code'

I'm stumped after the separation of the double helix tbh.
Transcription can be thought of as having three 'phases':

- Initiation - this is when RNA polymerase binds to the DNA double helix at special sequences at the start of a gene called promoters. This is mediated by a number of proteins known as transcription factors which form the initiation complex. You also get unwinding of the double helix and formation of a DNA-RNA hybrid on the template strand.

- Elongation - the RNA polymerase molecule translocates along the template strand and catalyses the addition of new ribonucloetides to the growing mRNA transcript though the formation of phosphodiester bonds. As it moves the DNA-RNA hybrid is maintained in a 'transcription bubble' by different parts of the polymerase molecule, known as the 'zipper' and 'rudder.' The growing mRNA transcript begins to emerge from the exit tunnel

- Termination - when RNA polymerase reaches a termination sequence on the DNA, a hairpin RNA structure is formed and a bunch of adenines are added to the end of the mRNA (around 200) - known as polyadenylation. The polymerase then comes apart from the DNA double helix. This is mediated by various proteins known as cleavage and polyadenylation factors.
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ImagineCats
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(Original post by Asklepios)
The free ribonucleotides needs to match up with the DNA strand (through Watson-Crick base pairing) in order for the mRNA strand to be synthesized as the right 'code'



Transcription can be thought of as having three 'phases':

- Initiation - this is when RNA polymerase binds to the DNA double helix at special sequences at the start of a gene called promoters. This is mediated by a number of proteins known as transcription factors which form the initiation complex. You also get unwinding of the double helix and formation of a DNA-RNA hybrid on the template strand.

- Elongation - the RNA polymerase molecule translocates along the template strand and catalyses the addition of new ribonucloetides to the growing mRNA transcript though the formation of phosphodiester bonds. As it moves the DNA-RNA hybrid is maintained in a 'transcription bubble' by different parts of the polymerase molecule, known as the 'zipper' and 'rudder'

- Termination - when RNA polymerase reaches a termination sequence on the DNA, a hairpin RNA structure is formed and a bunch of adenines are added to the end of the mRNA (around 200) - known as polyadenylation. The polymerase then comes apart from the DNA double helix. This is mediated by various proteins known as cleavage and polyadenylation factors.
The 3 phases aren't on my spec, but this is so helpful!

(Original post by Asklepios)
The free ribonucleotides needs to match up with the DNA strand (through Watson-Crick base pairing) in order for the mRNA strand to be synthesized as the right 'code'
I thought the mRNA was the right code anyway as in it already has the bases on it?

When the mRNA strand matches with the free nucleotides on the DNA strand does this change the sequence of codons on the mRNA? woaaaaaah
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Asklepios
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(Original post by ImagineCats)
I thought the mRNA was the right code anyway as in it already has the bases on it?

When the mRNA strand matches with the free nucleotides on the DNA strand does this change the sequence of codons on the mRNA? woaaaaaah
There is no mRNA prior to transcription. The cell has DNA and 'wants' to make RNA that has the same coding sequence as it. Only DNA is passed on through mitosis.
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mariapops
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(Original post by ImagineCats)
I get in the nucleus theres the DNA and the RNA polymerase comes along, breaking the H bonds and separating the strands causing them to uncoil and then the free RNA nucleotides in the nucleus go ahead and pair up with the now alone bases in the DNA- but whats the point of the mRNA's nucleotides joining with the DNA nucleotide only to be a single strand again?

I'm stumped after the separation of the double helix tbh.

Looked on youtube but no luck- can someone explain to me what happens after this? Maybe in baby terms so I can get my head around it, then throw in the key words.

Thanks!
Hey the reason it joins is because the separated DNA strand acts as a template! It's called the sense strand and whilst you're right in that mRNA is single stranded so in theory it would be pointless if it were double stranded but the reason why this happens is to make sure that the mRNA is complementary to the sense strand! If you just had a single strand straight away, the nucleotides would just be in a random order whereas they need the template dna so complementary nucleotides can form opposite it.
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PLM98
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I think RNA polymerase does not break the H bonds. It is helicase that breaks the H bonds and unwinds the double helix. Then free activated RNA nucleotides come along and bond to complementary bases on the DNA strand, which serves as a template, and RNA polymerase moves along the bases, joining them together by forming phosphodiester bonds between ribose and phosphate groups of neighbouring RNA nucleotides. They join to the DNA because the DNA is the template, the combination of bases on the DNA is complementary to that of the mRNA. Specific combinations of bases in DNA lead to the formation of mRNA strands with a specific combination of bases, which are then translated by ribosomes to form specific polypeptides.
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Asklepios
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(Original post by PLM98)
I think RNA polymerase does not break the H bonds. It is helicase that breaks the H bonds and unwinds the double helix. Then free activated RNA nucleotides come along and bond to complementary bases on the DNA strand, which serves as a template, and RNA polymerase moves along the bases, joining them together by forming phosphodiester bonds between ribose and phosphate groups of neighbouring RNA nucleotides. They join to the DNA because the DNA is the template, the combination of bases on the DNA is complementary to that of the mRNA. Specific combinations of bases in DNA lead to the formation of mRNA strands with a specific combination of bases, which are then translated by ribosomes to form specific polypeptides.
RNA polymerase has its own helicase activity so no additional helicase enzymes are needed for transcription. This is in contrast to DNA replication, as DNA polymerase does not have helicase activity.
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PLM98
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(Original post by Asklepios)
RNA polymerase has its own helicase activity so no additional helicase enzymes are needed for transcription. This is in contrast to DNA replication, as DNA polymerase does not have helicase activity.
Oh right, didn't know that, thanks. I am pretty sure the rest is right though haha did all this last year.
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User2334541
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Why don't we make a whole thread on A2 Biology on specific topics and revise together by using each other's knowledge and be able to get to the desired place that we want to be and get to a good positive outcome before the exams?
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mariapops
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(Original post by User)
Why don't we make a whole thread on A2 Biology on specific topics and revise together by using each other's knowledge and be able to get to the desired place that we want to be and get to a good positive outcome before the exams?
Good idea!
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Rigby16
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(Original post by ImagineCats)
I get in the nucleus theres the DNA and the RNA polymerase comes along, breaking the H bonds and separating the strands causing them to uncoil and then the free RNA nucleotides in the nucleus go ahead and pair up with the now alone bases in the DNA- but whats the point of the mRNA's nucleotides joining with the DNA nucleotide only to be a single strand again?

I'm stumped after the separation of the double helix tbh.

Looked on youtube but no luck- can someone explain to me what happens after this? Maybe in baby terms so I can get my head around it, then throw in the key words.

Thanks!
The RNA nucleotides need to join with DNA nucleotides on the DNA TEMPLATE STRAND so that when the phosphodiester bonds form between the RNA NUCLEOTIDES to make the MRNA stand, the MRNA has a complementary sequence of bases to the template strand and as it's complementary to the TEMPLATE strand the CODING strand (other strand) will have the same sequence of bases as MRNA which will code for a protein.
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ImagineCats
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(Original post by User2334541)
Why don't we make a whole thread on A2 Biology on specific topics and revise together by using each other's knowledge and be able to get to the desired place that we want to be and get to a good positive outcome before the exams?
Eh this is AS biology! New course- it's moved some A2 stuff to this course. Good idea though- wouldnt mind one for my AS this year and if you start the A2 one this year I'll be the heir to the thread for you
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ImagineCats
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(Original post by mariapops)
Hey the reason it joins is because the separated DNA strand acts as a template! It's called the sense strand and whilst you're right in that mRNA is single stranded so in theory it would be pointless if it were double stranded but the reason why this happens is to make sure that the mRNA is complementary to the sense strand! If you just had a single strand straight away, the nucleotides would just be in a random order whereas they need the template dna so complementary nucleotides can form opposite it.
Thank you!!!
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