THE ROLE OF RNA

DNA is the nucleic acid that is responsible for storing a cell's genetic information in the form of coded instructions. Because DNA does not leave the cell's nucleus, the instructions must be copied onto a messenger that can bring the genetic information from the nucleus to the ribosomes. Once here, the ribosomes make proteins, which control the biochemical pathways within the cell.

The nucleic acid that is responsible for performing these functions is RNA. RNA consists of a single chain of nucleotides. Each nucleotide contains a 5-carbon sugar (ribose), a phosphate group, and one of the following nitrogenous bases: guanine (G), cytosine (C), adenine (A), or uracil (U).

Although a cell contains many different forms of RNA, there are three main types that are involved in expressing the genetic code. The three main types of RNA are messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA). The process of transferring the genetic information from DNA to mRNA is called transcription. The process that decodes mRNA into a protein is known as translation.

PROCEDURE- Transcription:

  1. On the next page is a model of each of the mRNA nucleotides. Cut out each nucleotide.
  1. Assume that transcription has already taken place and that a portion of a DNA molecule with the code AGT GTT GCT initiated the formation of a RNA molecule with the code UCA CAA CGA. Each combination of three nitrogenous bases on mRNA is called a codon. Construct a model of this molecule using the nucleotides you have cut out.
  1. Tape this sequence to a piece of paper.

mRNA travels to the ribosomes where the genetic information must be decoded. tRNA, meanwhile, is present in the cell's cytoplasm. On each tRNA molecule, there are three exposed nitrogenous bases that will pair with a codon on mRNA.

Name: ______Date: ______Per: ___

PROCEDURE- Translation:

Attached to each tRNA on the end opposite its three bases (anticodon) is an amino acid. An anticodon specifies for each of the cell's 20 amino acids. By matching the tRNA anticodon to the mRNA codon, the correct amino acid is put into place in the ribosome.

PROCEDURE- Translation continued:

  1. Cut out the amino acid pieces and the tRNA pieces.
  1. Match the symbols to join the amino acids to their specific tRNA molecule.
  1. Answer the questions that follow.

a)Which amino acid is connected to the tRNA with the anticodon AGU? ______

b)Which amino acid is connected to the tRNA with the anticodon GUU? ______

c)Which amino acid is connected to the tRNA with the anticodon GCU? ______

  1. Now join the tRNA/Amino Acids to the mRNA model you have already constructed.
  1. Answer the following questions before you move on.

a)Can your tRNA molecule join with your mRNA molecule in any other configuration? ______EXPLAIN your answer ______

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b)Which nitrogenous base in mRNA complimentary base pairs (joins) with the

"A" of tRNA? ______

"U" of tRNA? ______

"G" of tRNA?______

c)What sequence of bases in tRNA can join only with base sequence AAA in mRNA? ______

Please label on your diagram:

  1. mRNA strand
  2. tRNA molecules
  3. Amino Acids
  4. Transcription
  5. Translation
  1. Color ONE monomer of RNA red on your mRNA chain.
  2. Color ONE codon blue.
  3. Color ONE anticodon green.
  1. What is the main function of DNA? ______
  1. Why does a disposable copy of DNA need to be made? ______

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  1. List the three ways RNA is different that DNA.

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  1. What is the monomer of RNA? ______
  2. What are the 3 parts that make up a monomer of RNA?

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  1. List the three main types of RNA.

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  1. The process of making mRNA from DNA is known as…______
  1. Where in the cell does the process (#10 above) happen? ______
  2. What is the process called that makes a protein based on the sequence of mRNA?

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  1. Where does the process (#12 above) happen in the cell? ______