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Translation

Translation. PROTEIN SYNTHESIS. Whole process Step by step- from chromosomes to proteins. 4 Components used in Translation. mRNA - the message to be translated into protein. Amino acids - the building blocks that are linked together to form the protein.

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Translation

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  1. Translation PROTEIN SYNTHESIS

  2. Whole process • Step by step- from chromosomes to proteins

  3. 4 Components used in Translation • mRNA- the message to be translated into protein. • Amino acids- the building blocks that are linked together to form the protein. • Ribosomes- the “machines” that carry out translation.

  4. tRNA(transfer RNA)- brings an amino acid to the mRNA and ribosome. • One end of a tRNA molecule has an anticodon that complements with an mRNA codon. • The other end has a specific amino acid. • A tRNA molecule with a particular anticodon always carries the same type of amino acid.

  5. How does translation occur? • The ribosome binds to the mRNA molecule. • The tRNA with the anticodon that complements the first codon on the mRNA binds to the first site on the ribosome. • Another tRNA with the anticodon that complements the second codon on the mRNA binds to the second site on the ribosome.

  6. A peptide bond forms between the first two amino acids. • The first tRNA leaves, and the ribosome moves along the mRNA to the next codon. • The next tRNA brings in the next amino acid, and a peptide bond is formed between this amino acid and the growing amino acid chain. • The process continues with the ribosome moving along the mRNA molecule and the amino acids linking together until a STOP codon is reached.

  7. The CODE of translation

  8. CODONS mRNA nucleotides are translated in groups of 3 called codons. AUGCACUGCAGUCGAUGA

  9. Each codon codes for a specific amino acid. 20 different amino acids can be used in different combinations to form a protein. For example: mRNA codonamino acid AAU asparagine CGC arginine GGG glycine

  10. Amino Acid sequence determines the 3-D protein shape • Interactions between amino acids cause folding and bending of the chain Examples: • positive (+) and negative (-) parts of amino acids are attracted to each other. • hydrophobic regions are attracted to each other • Folding http://www.stolaf.edu/people/giannini/flashanimat/proteins/hydrophobic%20force.swf • Structure levels http://www.stolaf.edu/people/giannini/flashanimat/proteins/protein structure.swf

  11. How is the amino acid sequence determined? • The mRNA • Each codon is a code for one amino acid DNA sequence: T A C C G A G A T T C A mRNA sequence: A U GG C UC U AA G U amino acid sequence: Met -- Ala -- Leu -- Ser

  12. Your turn • Complete the “Translation Practice” worksheet

  13. Mutations Mutation- a change in the DNA nucleotide sequence Mutations can cause subtle or dramatic effects on observed traits in individuals

  14. Observed trait DNA mRNA protein translation protein function (enzyme activity) transcription How does your DNA determine your traits? • Remember: • Traits are determined by the functions of proteins • Protein function is determined by protein shape • Protein shape is determined by amino acid sequence

  15. Mutations can change the amino acid sequences of proteins DNA sequence: T A C C G A G A T T C A mRNA sequence: A U GG C UC U AA G U amino acid sequence: Met -- Ala -- Leu -- Ser DNA sequence: T A C C G A G A T T C A mRNA sequence: A U GG C UA U AA G U amino acid sequence: Met -- Ala -- Iso -- Ser T

  16. How does this mutation change the amino acid sequence? (Original) DNA sequence: A A T G C A T A T G C A mRNA sequence: U U AC G UA U AC G U amino acid sequence: Leu -- Arg -- Ile -- Arg (Mutated) DNA sequence: A A T T C A T A T G C A mRNA sequence: U U AA G UA U AC G U amino acid sequence: Leu -- Ser -- Ile -- Arg

  17. 3 types of mutations Substitution Insertion Deletion T T A C C G A G A T T C A Substituting one nucleotide for another. T A C C G A T G A T T C A Inserting one or more nucleotides T A C C G A G A T T C A Deleting one or more nucleotides

  18. Homework • Complete both sides of the “Mutations practice”. You will learn how some mutations can affect the amino acid sequence of proteins • Consider how severe of an effect each mutation would have on the ability of the protein to function.

  19. Warm-up • We’ve studied transcription, translation, and replication. A mistake in which of these processes would result in a mutation?

  20. Which mutations had the biggest effect on the protein sequence? WHY? • Which mutations had the smallest effect on the protein sequence? WHY? • Which examples would you predict to have the biggest effects on a trait? WHY? • Which examples would you predict to have the smallest effects on a trait? WHY?

  21. Different types of mutations happen Substitution Insertion Deletion T T A C C G A G A T T C A T A C C G A T G A T T C A T A C C G A G A T T C A

  22. Frameshift mutations • One or more than one nucleotide can be added or deleted with insertion and deletion mutations. • If the number of nucleotides is not a multiple of 3, it is called a frameshift mutation. • Why do we call this a frameshift mutation? • Can substitution mutations cause frameshifts? Explain why or why not.

  23. Consequences of mutations… • If a mutation in sperm or egg DNA is not fixed, the new sequence of DNA is passed on to offspring. • Over generations, more mutations accumulate. • As a result, differences occur between people’s DNA sequences!

  24. How much variation in DNA exists between 2 people? Hemoglobin (beta) gene sequence from person A

  25. How much variation in DNA exists between 2 people? Hemoglobin (beta) gene sequence from person B

  26. How much variation in DNA exists between 2 people? • About 1 in every 1,000 nucleotides is different between 2 people • (0.1% difference means 99.9% identical) • We have about 3 billion nucleotides in all, so that means there are about 3 million nucleotide differences between 2 people

  27. What is the observed effect of mutations? • No Effect (think about it: are there 3 million differences between 2 people?) • Why? • Some mutations code for the same amino acid • Most mutations are in sequences of DNA between genes. • Variation – there are a variety of traits in a population.

  28. Genetic diseases • Many alleles are harmless, but some can cause specific diseases. • One disease caused by a specific mutation is sickle cell anemia

  29. Genetic diseases Many alleles are harmless, but some can cause specific diseases. They can be dominant or recessive. To determine whether a disease is genetic, we trace the family history of a disease by creating a type of family tree called a pedigree.

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