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Hi! 
Is it possible to ask a question? I really need to understand this and I'm struggling.

I don't understand how RNA codes the amino acids. I do understand that there is a mRNA and a tRNA and that there is more than one code for an amino acid. This is what's confusing, I copied something from your website.

"This cousin is the cgc-transfer-RNA, and she holds the correct amino acid on her top. Her amino acid is called 'alanine'. The cgc anti-codon on her bottom matches up with my codon gcg.  In nucleotide language, gcg means: Put alanine here. "

Can the cgc anti-codon match up with the gcg because they both code for alanine? Thanks so much for the trying to help.
Julie

Hi Julie,
This is a confusing concept until you get it.

The codon and anti-codon really attach to each other. The 'c' on one attaches to a 'g' on the other, and 'a' attaches to 't'. One codon will not mate, or attach, to the wrong anti-codon because of this.

Let's try this with a silly analogy. Let say that you and a girl friend and both of your boyfriends get bunches of clones. Then you all hold hands in threes and make triplet codons and triplet anti-codons. The only way a codon will match an anti-codon is if the anti-codon order has the correct boyfriend across from the correct girl friend.

Let me know if this helps some. If you need more information or another approach, just let me know and we will try again.

The fact that you are trying to understand this shows that you could be a very good scientist indeed ! Keep up the good effort.
Dr. Pat

Thanks I get this part.
 Are you up for one more? I think my problem is "can't teach an old dog new tricks".  I thought I understood the wobble hypothesis until I was given a situation. I was given 2 strands of DNA and one strand of mRNA all with some fill in the blank spots.  I'm supposed to fill in the blanks and match up the codons with amino acids. I'll put red letters in the spots that were blank the way I think it should be. They may be wrong.

DNA

A C G C T A C G C A ? T A C T C T C A A G T C G T A C G

T G C G A T G C G T ? A T G A G A G T T C A G C A T G C

mRNA

U G C G A U G C G U G A U G A G A G U U C A G C A U G C

polypeptide chain given

methionine-arginine-asparate-alanine ______ serine-alanine-cysteine

I see the serine,alanine,cysteine segment but the rest doesn't seem to be right. I sincerely appreciate your help but will understand if this question is too much to ask.
Julie

Hi Julie,
I take it from your "old dog" comment you are not in high school.

First, no red letters came through. But, I do see a ? in the DNA strands. You can tell that the top strand is a C and the bottom a G from the sequence in the mRNA.

There are three AUG's in your mRNA, but the first seems to be the start of the particular amino acid sequence. I can get the
meth-arg-asp-xxx-____-ser-ala-cys. 
But I do not get the first ala (I put xxx above), I get a codon of GAG which codes for glu, not ala. So, there may be a small error in your question, and not your answer.

As for the wobble hypothesis, it is to explain the multiple codons that code for a single amino acid. Since there are 64 combinations of triplets and only 20 amino acids, something has to happen in nature. Scientists so came up with this hypothesis to explain the variability of codons. They do see a pattern in the third position of the codon being the one with the most variation in the set of triplets that code for any one amino acids. They suggest that that position's "wobble" allows a bit of genetic 'give' to the DNA sequence before a mutation causes havoc in protein sequences. Also, this "wobble" in the triplets allow for less tight binding between codons and anti-codons, so that the correct amino acid can be incorporated into a peptide chain, even if a slight mistake occurs with the t-RNA recognition. That leaves the entire system a bit resistant to 'mistakes'.
Dr. Pat

Dr. Pat,
Yes, I am 40 and have just now figured out what I want to do (I think).

But your website is just my speed!! So please, explain things to me like you would a high school student :)

That's the problem I'm having. The question is directly from the worksheet. I, too, was beginning to think there was an error in the question. Unfortunately, I'm taking a distance education course and the instructor is not very "interactive". You've been much more helpful. I will contact the instructor.

Thanks again for your assistance!!
Julie

Dr. Pat,
Why does it take DNA to make DNA?
Samantha

  Hi Samantha,
You have asked an excellent question. This question was asked by scientists for decades. The easiest answer is as follows:

It does not take DNA to make DNA.  In most cells and viruses, DNA is the primary template (or sequence used to make duplicates).  But, in some viruses, RNA is used to make messenger RNA and DNA.  These kinds of viruses are called "retro-viruses" because they seem to be doing it backward from all other cells and viruses.

The task of copying DNA or making messenger RNA is a large one. And, except for those retro-viruses, cells and the rest of the viruses only have the set of enzymes needed for using DNA as the template. It is the only way cells and most viruses can do it.

Keep asking those questions. You show a keen ability and you could be a very good scientist.
Dr. Pat

 

 

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