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transcription and translation. HELP!!!

Argh, i never understood it in class, and so am trying to find out what exzactly happens.
Could someone walk me through transcription step by step, as biology mad..com and my two textbooks say conflicting things. one says that RNA is made, the other mRNA is made. argh

Reply 1

joeybee

The start of each gene on DNA is marked by a special sequence of bases.
DNA unwinds by enzyme action involving breaking of hydrogen bonds.
The enzyme RNA polymerase moves along the sense strand containing the genetic code.
The enzyme catalyses the assemble of an mRNA molecule by matching nucleotides.
When mRNA is made the base Thymine is replaced by Uracil, so base pairing is A+U and G+C.
The mRNA molecule peels off the gene and passes out of the nucleus.

That is what i have so far, now is that correct or are there bits missed out???

Reply 2

gyrase

joeybee

That is what i have so far, now is that correct or are there bits missed out???

Pretty much correct. :smile:

That's a description of transcription. Translation is using the mRNA code to assemble polypeptides in ribosomes, by the mRNA strands joining with amino acid binded tRNA molecules in which only specific amino acids are assembled together according to the mRNA code. These produce large polypeptide proteins.

Reply 3

J2K

Simple run through:

1. DNA Unzips as Hydrogen Bonds between bases break
2. RNA Polymerase binds to the sense strand and assembles free nucleotides to form an mRNA molecule
3. The sequence of bases on the mRNA is complimentary to the sequence of bases on the DNA (i.e. Purines (Adenine and Guanine) bind with Pyramidines (Uracil, Thymine or Cytosine)).
4. The mRNA is edited so any introns (non-coding DNA) are no longer present in the base sequence.
5. The mRNA molecule leaves the nucleus and binds to a ribosome.
6. tRNA molecules are activated using ATP and this joins an amino acid to them. Specific tRNA molecules carry a specific amino acid.
7. A sequence of three bases on the mRNA (the codon) is complimentary to a set of three bases on the tRNA molecule (anticodons).
8. The tRNA molecule binds to the mRNA and then leaves to collect another amino acid.
9. Therefore the sequence of bases on the mRNA molecule determines the sequence of amino acids.
10. Peptide bonds form between the amino acids and a polypeptide is formed.

Hope that makes sense =). If you do AQA Biology A, six of those points should be enough to get you six marks in one of those big questions.

Reply 4

joeybee

thankyou very much :biggrin:

I'd rep you both but i have already repped someone today! maybe tomorrow.
i think i am well on my way to finnishing revision notes on dna, protein synthesis and genetic eng, i only have to write up notes now for forensic biology and immunology, it's all going to plan :smile:

i hope the exam is a nice one this time, well as nice as they can be.

Reply 5

MadNatSci

joeybee

biology mad..com and my two textbooks say conflicting things. one says that RNA is made, the other mRNA is made. argh

Just one point: mRNA is just a type of RNA. So they are both right :smile:

It's just that mRNA is a more specific term - it's RNA that codes for proteins, specifically, rather than RNA that does a number of other jobs.

(Sorry, I used 'specific' twice in quick succession but I can't be bothered to work out how to rephrase this morning - exams to take! :biggrin:

)

Reply 6

J2K

Oh yeah, forgot to mention.

mRNA = Messenger RNA
tRNA = Transfer RNA

Reply 7

Miss Amy

Lol, Ive always had a problem with this aswell, so yesterday i decided to sit down and go over it untill i understood it.....I come on here today and theres a full description!! lol

Well atleast this thread backs up my knowledge of it now aswell :smile:

Some nice, simple descriptions there guys btw, nice one!