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a couple of questions about bio, please :( - January 29th 2009, 06:22 PM

1. Had Chargaff's data from a single source indicated the following, what might Watson and Crick have concluded?

A= 29% T=19% C=21% G=31%

Why would this conclusion be contradictory to Franklin's data?

(Basically, I don't understand what the question is asking)

2. Which is the least harmful and why?
An addition in an intron region versus an addition in an exon region?

3. Describe the consequences to protein synthesis if the following were inactivated.

- tRNA

- Ribosomes

4. The following is a sequence of DNA for a hypothetical peptide. Translate this sequence into protein using the genetic code

5'-AAGTACAGCAT-3'
3'-TTCATGTCGTA-5'

(I'm not sure which stage of protein synthesis I translate the code into, replication, transcription, or translation)

5. Why does more than one sequence exist when doing mRNA sequences? (It's talking about the genetic code, that even though a codon may have different base pairs, it could still be the same amino acid)

6. Hypothetically, there are 126 amino acids and only 5 nucleotides available. Calculate the minimum number of nucleotides required for all 126 amino acids.

7. Explain why amino acids cannot be coded with just two base pairs.


I know it's a lot of questions, but I need serious help
   
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Re: a couple of questions about bio, please :( - January 29th 2009, 08:21 PM

please helpppp
   
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Re: a couple of questions about bio, please :( - January 30th 2009, 09:41 AM

Quote:
Originally Posted by iamverybeautiful View Post
1. Had Chargaff's data from a single source indicated the following, what might Watson and Crick have concluded?

A= 29% T=19% C=21% G=31%

Why would this conclusion be contradictory to Franklin's data?

(Basically, I don't understand what the question is asking)

2. Which is the least harmful and why?
An addition in an intron region versus an addition in an exon region?

3. Describe the consequences to protein synthesis if the following were inactivated.

- tRNA

- Ribosomes

4. The following is a sequence of DNA for a hypothetical peptide. Translate this sequence into protein using the genetic code

5'-AAGTACAGCAT-3'
3'-TTCATGTCGTA-5'

(I'm not sure which stage of protein synthesis I translate the code into, replication, transcription, or translation)

5. Why does more than one sequence exist when doing mRNA sequences? (It's talking about the genetic code, that even though a codon may have different base pairs, it could still be the same amino acid)

6. Hypothetically, there are 126 amino acids and only 5 nucleotides available. Calculate the minimum number of nucleotides required for all 126 amino acids.

7. Explain why amino acids cannot be coded with just two base pairs.


I know it's a lot of questions, but I need serious help
I've recently finished 2nd year cell biology, so I'll try to make it very simple as I don't know your level of understanding. Don't copy my answers, they're probably not good enough for full marks. You'd need to explain them more, word it better, etc... .

One thing to know, for question 3, if you see a question that you think may cause a changed protein, that can be detremental to the cell. In some cases, it could be lethal. For these problems, think a) what the question wants and b) for the things in the question, what mechanisms underly the problems. However, this requires a thourough understanding which takes time to get.

1) Franklin suggested A%=T% and G%=C% because those two pair up under normal circumstances. Since this data is completely different, it's inconsistent.

2) Recall, for a mature mRNA to be produced several processes have to occur. One of them is splicing out the intron. The exons are joined together once intron is spliced, help mRNA mature and the proteins are synthesized. If the exons (things that remain) are changed, the mRNA will be changed and the proteins will be changed. For the introns, they're spliced out so GENERALLY it's less harmful if they're changed, however, it depends where the change occurs because there are some important sites on the intron. However, at a basic level, introns and less harmful.

3) Recall what each of the molecules are responsible for. tRNA's are adapter molecules to bring amino acids to mRNA. If the adapter is changed, either the wrong amino acid is brought (so wrong amino acid order of the protein) or the adapter is useless and cannot bring anything. Ribosomes are large multiprotein complexes that synthesize proteins. If they're changed, the proteins being produced could be changed.

4) This you can do by yourself. You'll need a genetic code, which should be in your textbook or online and look at 3 bases (the codons) and then look on the genetic code for what amino acids they corrospond to. You need to be careful though, there can be 3 reading frames. If this is at the beginning of the protein, you need to get AUG (methionine). If it's in the middle, you don't want a stop codon (UAA, UAG or UGA). If it's at the end, you do want to see a stop codon at the end. Remember, this is a DNA sequence so everywhere I've typed "U" replace that with "T".

You just translate the code into the amino acids. From that, it's hard to tell what stage unless you're observing the cell replicate, which you're not, or if the question gives background information.

5) The genetic code has several properties, one of them is redundancy. The reason takes a slight amount of thinking (hint: tRNA's). This part is the part I suggested that may be over your head. If you have a picture of a tRNA, take it out to follow along. The bottom of the tRNA is the anticodon loop. One of the 3 anticodons, I think it's the 3rd is a "wobble base". It can take more than 1 base, whereas the other 2 cannot (check, it may be the 1st or 3rd base). This allows 1 tRNA to transfer multiple amino acids to the mRNA.

6) I think this is just a simple division.

7) Simple, the modern genetic code uses triple amino acids or codons, not 2. If you have 2, then the genetic code couldn't produce any amino acid. Also, if it ends with 2, molecules to attach may be looking for 3 and thus, may not attach properly.
   
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