DNA and RNA help!?

Question

I have 4 short questions....

The DNA sequence for one small segemnt of a gene is

"ATG GCG TAT GAC CTA"

1. How is this segment of DNA transcribed into messenger RNA?

2. wHAT is the nucleotide sequence of the mRNA that corresponds to this gene segment?

3. What are the transfer RNA (tRNA) anticodes that bind to the mRNA molecule whose sequence was determined in the above question?

4. How is the nucleotide sequence in the mRNA translated into a polypeptide sequence?


Please be specific, I can't help my son with homework if I dont understand myself.

Answer 1

I've come across to this exact question by another user a couple of days ago.

For parts how transcription and translation occur, you really need to refer to textbooks. I don't know your background so I can't start analyzing the processes. I'll refer you to the book "molecular biology of the cell" for a very well written explanation with great figures. You can access it freely on-line. Just go to
http://www.ncbi.nlm.nih.gov/books/bv.fcgi?
Through the search box you can access the contents of the book.

As far as the exact sequences are concerned...

BE VERY CAREFUL

DNA is a double helix. One strand will code for the protein and the other is used as a template for the polymerase to use in order to make the mRNA.

BY CONVENTION, the GENE sequence is the CODING sequence and NOT the sequence of the template.
They give you the GENE sequence.
Thus the sequence of them RNA is going to be the same with U instead of T.

5'-AUG GCG UAU GAC CUA-3'

Teachers and students get usually confused by this and sometimes even the questions are poorly formulated and many get confused if the DNA sequence they are given is the template or the coding sequence; sometimes even the teachers themselves ask for the wrong answer! However when you are working in the field you cannot make/afford such mistakes.

The anticodons of the transfer RNAs have to be complementary to the codons. Each codon consists of 3 bases. A and U are complementary with each other, G and C are again complementary with each other.

The first codon is AUG so the complex of the codon and the anticodon is

5'-AUG-3'
3'-UAC-5'

BUT by convention nucleic acid sequences are written in the 5'->3' direction, so the anticodon is written CAU

For GCG, you get CGC
For UAU you get AUA
For GAC you get GUC
For CUA you get UAG


The protein sequence will be
MAYDL in single letter code or
Met-Ala-Tyr-Asp-Leu in three letter code.

You can use http://au.expasy.org/tools/dna.html...
to translate any sequence

Answer 2

I guess I should try this one....
1. A segment of DNA is transcribed into RNA by adding bases that are complementary to those in the DNA segment in the same order. mRNA does not contain Thymine. Instead it has Uracil.

2. The sequence of mRNA corresponding to this DNA segment: UAC CGC AUA CUG GAU

3. The anticodons in tRNA : AUG, GCG, UAU, GAC and CUA.

4. The triplet codons in the mRNA. Each of these represent an aminoacid. tRNAs are attached to specific aminoacids. The tRNA contains "anticodons" that are complementary to the triplet "codon" present in the mRNA. For example, AUG in the mRNA is recognized by Methionine carrying aminoacid (with an anticodon UAC).

For the aminoacid sequence corresponding to the mRNA sequence refer the genetic code dictionary that you will find in almost all the standard molecular biology books.

Hope this answers all your questions.

Wonder what grade your son is in?????

Answer 3

Everything except for e is technically correct. RNA is transcribed by the ribosome, not produced by. D can be different depending on the situation; like for example, RNA, not DNA, is used in the HIV virus because RNA is somewhat more stable and more useful in a retrovirus. B is commonly true, but to the best of my knowledge, double stranded RNA does exist.

Answer 4

I'll give you a web site that explains all this stuff. It also has a DNA calculator. Just type in your sequence, and it will do the rest for you.

Hope this helps you!

http://www.vivo.colostate.edu/molkit/translate/index.html