he3456
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q) mRNA is used during translation to form polypeptides. describe how mRNA is produced in the nucleus of a cell;

a)
1. Helicase;
2. Breaks hydrogen bonds;
3. Only one DNA strand acts as template;
4. RNA nucleotides attracted to exposed bases;
5. (Attraction) according to base pairing rule;
6. RNA polymerase joins (RNA) nucleotides together;
7. Pre-mRNA spliced to remove introns.

why would you not write about RNA polymerase binding to a region of non coding DNA...etc. instead since isn't DNA helicase related to DNA replication rather than mRNA formation?
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RM_Asclepius
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(Original post by he3456)
q) mRNA is used during translation to form polypeptides. describe how mRNA is produced in the nucleus of a cell;

a)
1. Helicase;
2. Breaks hydrogen bonds;
3. Only one DNA strand acts as template;
4. RNA nucleotides attracted to exposed bases;
5. (Attraction) according to base pairing rule;
6. RNA polymerase joins (RNA) nucleotides together;
7. Pre-mRNA spliced to remove introns.

why would you not write about RNA polymerase binding to a region of non coding DNA...etc. instead since isn't DNA helicase related to DNA replication rather than mRNA formation?
DNA helicase is simply an enzyme that overcomes hydrogen bonds between the two strands of DNA and is therefore required in both DNA replication and mRNA formation. RNA polymerase does not bind to the non-coding strand at all, but it binds to the RNA nucleotides that have undergone complementary base pairing with the TEMPLATE STRAND.
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he3456
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(Original post by RM_Asclepius)
DNA helicase is simply an enzyme that overcomes hydrogen bonds between the two strands of DNA and is therefore required in both DNA replication and mRNA formation. RNA polymerase does not bind to the non-coding strand at all, but it binds to the RNA nucleotides that have undergone complementary base pairing with the TEMPLATE STRAND.
ohh, and the RNA polymerase simply binds the new nucleotides together?
its just my textbook says soemthing completely different to the markscheme
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A.shaquile
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Can someone explain 3 to 5 leading and lagging strand in DNA replication? Thanks.
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RM_Asclepius
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(Original post by he3456)
ohh, and the RNA polymerase simply binds the new nucleotides together?
its just my textbook says soemthing completely different to the markscheme
Yes that is correct. I would say the RNA polymerase catalyses the formation of phosphodiester bonds between adjacent RNA nucleotides (through hydrolysis of ATP) just to be specific.
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Exdoz
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(Original post by he3456)
q) mRNA is used during translation to form polypeptides. describe how mRNA is produced in the nucleus of a cell;

a)
1. Helicase;
2. Breaks hydrogen bonds;
3. Only one DNA strand acts as template;
4. RNA nucleotides attracted to exposed bases;
5. (Attraction) according to base pairing rule;
6. RNA polymerase joins (RNA) nucleotides together;
7. Pre-mRNA spliced to remove introns.

why would you not write about RNA polymerase binding to a region of non coding DNA...etc. instead since isn't DNA helicase related to DNA replication rather than mRNA formation?
(Original post by RM_Asclepius)
Yes that is correct. I would say the RNA polymerase catalyses the formation of phosphodiester bonds between adjacent RNA nucleotides (through hydrolysis of ATP) just to be specific.
Yep this is correct. RNA polymerase is the same as DNA polymerase during DNA semi-conservative replication.It basically forms the backbone for the new strand which is the mRNA strand
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RM_Asclepius
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(Original post by A.shaquile)
Can someone explain 3 to 5 leading and lagging strand in DNA replication? Thanks.
When DNA helicase attaches to a molecule of DNA, it 'unzips' the molecule in the 5' to 3' direction. As this is occurring DNA polymerase has attached to the parts of the two strands that are exposed. As DNA polymerase is an enzyme that has a specific shape, it may only join nucleotides and move up the DNA in the 5' to 3' direction, we know however that the two strands of DNA in a molecule are antiparallel which means that one of the strands will run in the 3' to 5' direction. This means that on the 5' to 3' strand, that DNA helicase and polymerase are running in the same direction, this is known as the leading strand. The other strand is known as the lagging strand because as we mentioned before, DNA polymerase can only run in the 5' to 3' direction which means that in this strand, it has to keep stopping and reattaching to the newly exposed bases created by the action of DNA helicase. I found this link that explains it pretty well: https://www.biologyexams4u.com/2013/...l#.XgHz0C10dQI
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