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Genetics: transcription translation help!

  1. Jul 29, 2004 #1
    OK i just want some clarification on what i am doing is right if it is wrong please help me

    first i have a template strand for a part of a DNA
    this is

    now this strand is decoded via the process of transcription into mRNA where it moves to the cytoplasm.

    the mRNA formed is
    now with this the mRNA attaches to ribosomes and each amino acid is brought to the mRNA on ribosomes by tRNA. these tRNA molecules have 3 bases that make up an anticodon.
    this will form

    so far is my process right of transcription / translation.

    now the questions

    1. how many trna molecules did you make?
    would this be 7 since there are 7 anticodons?
    2. how many different trna molecules did you make?
    *** not sure about this ***i would assume 7 since each trna anticodon are not the same order or is it each trna anticodon gives a different amino acid
    3.how many different tRNA molecules would you expect to find in a cell
    *** also had problem*** would this be 64 as 4^3 gives the different instructions i would find in a cell or would it be 20 as there are only 20 different amino acids that can be formed.
    4.how many amino acids are there in the protein chain you made? how does this number relate to the number of triplets in the DNA molecule you started with? How does the number of amino acids relate to the number of codons in your mRNA molecule?
    ** please check***would there be 7 amino acids since this is the number of triplets, codons and anti-codons. the number of amino acids that are in the protein chain i made will relate to as the number of triplets, codons and anticodons is the number of amino acids that will be produced.

    can someone please give me the best answer for this general question
    1. what is meant when we say the 2 strands in a DNA molecule is anti-parallel.
  2. jcsd
  3. Jul 29, 2004 #2


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    You should translate the mRNA. You will find that the question as a tricky part.

    32 different kinds of tRNA in a typical eukaryotic cell. Thus most amino acids have more than one tRNA responsible for them. The anticodon on the tRNA may change and also there codon bias in cells. Therefore some codons are used more often than other (http://www.iscb.org/ismb2004/posters/danny-kATactcom.co.il_271.html [Broken]). The third (wobble) position in the codon also allow for some limited codon (http://www.web-books.com/MoBio/Free/Ch5C4.htm)

    Again translate the mRNA.

    One strand goes 5'-3' whereas the other goes 3'-5'. It like two arrow that are parrallel but point in different direction
    Last edited by a moderator: May 1, 2017
  4. Aug 6, 2004 #3

    1) 7 tRNAs are needed. The first codon (AUG) is the start of the open reading frame, but encodes the amino acid Met.

    2) 6 *different* tRNAs are needed because the codons ACU and ACG both encode the amino acid Thr. Each amino acid has its own tRNA synthesase, and subsequently its own tRNA, but since different codons can encode the same amino acid, different codons can utilize the same tRNA.

    3) 20 different tRNAs are found in a typical cell. However, there are some exceptions to this rule, as in some bacteria that lack a tRNA for glutamine. In that case the tRNA for glutamate is used and glutamate is coverted to glutamine via an amination reaction.

    4) 7 amino acids are encoded for this protein, one amino acid per codon, including the start codon (AUG). It should also be noted that the sequence of codons for this problem does not include a stop sequence (UAG, UGA, or UAA).
    Last edited: Aug 6, 2004
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