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DNA Translation - Chapter 8.5

Last updated over 6 years ago
23 questions
Note from the author:
Video clip and text describing how a protein is made during translation at the ribosome.
Translation is the process that converts an mRNA message into a polypeptide, or protein. An mRNA message is made up of combinations of four nucleotides, whereas proteins are made up of twenty types of amino acids. The mRNA message is read as a series of non-overlapping codons, a sequence of three nucleotides that code for an amino acid. Many amino acids are coded for by more than one codon. In general, codons that code for the same amino acid share the same first two nucleotides. Three codons, called stop codons, signal the end of the polypeptide. There is also a start codon, which both signals the start of translation and codes for the amino acid methionine. This genetic code is the same in almost all organisms, so it is sometimes called the universal genetic code.

Although tRNA and rRNA are not translated into proteins, they play key roles in helping cells translate mRNA into proteins. Each tRNA molecule folds up into a characteristic L shape. One end has three nucleotides called an anticodon, which recognize and bind to a codon on the mRNA strand. The other end of the tRNA molecule carries a specific amino acid. A combination of rRNA and proteins make up the ribosome. Ribosomes consist of a large and small subunit. The large subunit has binding sites for tRNA. The small subunit binds to the mRNA strand.

At the start of translation, a small subunit binds to an mRNA strand. Then the large subunit joins. A tRNA molecule binds to the start codon. Another tRNA molecule binds to the next codon. The ribosome forms a bond between the two amino acids carried by the tRNA molecules and pulls the mRNA strand by the length of one codon. This causes the first tRNA molecule to be released and opens up a new codon for binding. This process continues to be repeated until a stop codon is reached and the ribosome falls apart.
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Last Name, First Name

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This amino acid chart will be helpful as you complete the worksheet on translation.
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The reading frame is a series of 3 non-overlapping nucleotides read in order.

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A codon is a three nucleotide sequence that codes for an protein.

Codons code for amino acids.
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The common language is the genetic code (A, C, G, T) that is shared by almost all organisms.

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Start codons signal the start for translation to occur. Give the code for the start codon methionine.

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Stop codons signal the end of translation. Give the three stop codons typing them in alphabetical order with one space between each triplet.

A triplet is a three letter codon
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The ribosome consists of a large subunit that binds to a transfer RNA (tRNA).

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The ribosome also has a small subunit that binds to the messenger RNA (mRNA).

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An anticodon is the 3 nucleotides on a tRNA molecule that bind to a complimentary mRNA.

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A transfer RNA (tRNA) finds and carries a specific amino acid from the cytoplasm to the ribosome. One end has a specific anticodon and the other end attaches to a specific amino acid.

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Label the parts of the ribosome during translation. #1 is pointing to the

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Label the parts of the ribosome during translation. #2 is pointing to the special type of bond that is created between the amino acids as a protein is created. It is called a

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#4 is pointing the the part that locates and brings in an amino acid to the ribosome. It is called a

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#3 is pointing towards one part of the ribosome. It is the

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#5 is pointing to the specific three nucleotide sequence on the mRNA. This 3 nucleotide sequence is called a

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#6 is pointing to a specific part of the ribosome. It is the

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#7 is pointing to the strand of genetic material that has the code for the protein. It is called

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#8 is pointing to the bottom part of the tRNA. The special 3 nucleotide sequence is called a

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Under Process. #1 - the ribosome assembles at a start codon; complementary tRNA molecules pairs with the exposed codon.

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As the ribosome bonds the amino acid to the start codon; it breaks the bond between the amino acid and tRNA.

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The ribosome pulls the mRNA strand the length of the codon; first tRNA returns to cytoplasm and another codon is exposed for the next tRNA binding.

Now that you have all the terms down. Go to the sites in the assignment and practice making mRNA (transcription) and proteins (translation).