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BIOL 1408 FINAL

BIOL 1408 FINAL. PROTEIN SYNTHESIS. DNA (DEOXYRIBONUCLEIC ACID). DNA is a double-stranded chain of nucleotides. It is arranged in the shape of an alpha helix, the strands are twisted and coiled. NUCLEOTIDE STRUCTURE.

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BIOL 1408 FINAL

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  1. BIOL 1408 FINAL PROTEIN SYNTHESIS

  2. DNA (DEOXYRIBONUCLEIC ACID) • DNA is a double-stranded chain of nucleotides. • It is arranged in the shape of an alpha helix, the strands are twisted and coiled.

  3. NUCLEOTIDE STRUCTURE • An individual nucleotide is composed of 3 parts: A 5-sided sugar, a phosphate, and a nitrogenous base. • There are 2 classes of nitrogenous bases: Purines and Pyrimidines. • Adenine and Guanine are purines. • Thymine, Cytosine, and Uracil are pyrimidines.

  4. COMPLIMENTARY BASE PAIRING • Complimentary pairing occurs between the nitrogenous bases on the opposing strands of nucleotides in the DNA strand. • Adenine always pairs with Thymine. • Guanine always pairs with Cytosine.

  5. PROTEIN SYNTHESIS • Protein synthesis involves 2 stages: Transcription and Translation. • Transcription involves copying a segment of DNA. • Translation involves reading the copy to make a protein.

  6. TRANSCRIPTION • Occurs in the nucleus of the cell. • The enzyme DNA transcriptase “unzips” a segment of the DNA strand and exposes the nucleotides. • Free nucleotides match up with one side of the DNA strand and form a strand of messenger (mRNA). • In mRNA, Thymine is replaced by Uracil and pairs with Adenine.

  7. (mRNA) Messenger RNA • mRNA is simply a coded copy of one side of the exposed DNA strand. • The end result of transcription is a strand of mRNA. • mRNA stands for “messenger ribonucleic acid”. It carries the message of the DNA.

  8. TRANSLATION • Occurs at a ribosome in the cytoplasm of the cell. • The mRNA strand attaches to a ribosome (“Protein Factory”). • The mRNA strand is “read” 3 bases at a time. • This triplet code on the mRNA strand is known as a codon. • Each codon codes for a single amino acid.

  9. TRANSLATION (cont.) • In the cytoplasm are transfer RNA (tRNA) molecules that carry specific amino acids. • These tRNA molecules have a 3 base code sequence attached to them. The 3 base sequence on the tRNA molecule is called an anti-codon. • When the anti-codon of a tRNA molecule matches with a codon on the mRNA strand, the amino acid carried by the tRNA is dropped off at the ribosome.

  10. TRANSLATION (cont.) • As this process continues, a string of amino acids forms at the ribosome. • This string of amino acids is called a polypeptide. A long polypeptide chain is a protein. • When the entire mRNA strand is “read” and all the amino acids dropped off at the ribosome, the making of the protein is complete. • The protein breaks free from the ribosome and is transported to where it is needed.

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