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Protein Synthesis: From Genetics to Traits

Explore gene expression and protein production, from decoding DNA to building proteins, reviewing DNA structure, RNA types, and the central dogma process. Learn about mutations and their impact on gene expression and traits.

madonna-murphy
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Protein Synthesis: From Genetics to Traits

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  1. Gene Expression From a gene to a protein

  2. Central Dogma • (Crick 1958) • Determines the genetic flow of information

  3. Central Dogma First step: a genetic message from DNA is to copied (transcribed) into mRNA, which contains the code for making proteins Second step: is to decode mRNA into a polypeptide chain which builds a protein.

  4. Functions of a Protein Functions of Protein: • Structural • muscle, hair • Chemical • antibodies, hormones, enzymes (regulate all chemical reactions in cells)

  5. Proteins • Proteins are made, from mRNA, by joining amino acids into long polypeptides (which are proteins) • There are only 20 naturally occurring amino acids

  6. Review of DNA • DNA is the genetic material • DNA codes for different genes • Genes are codes for a protein which determines different traits

  7. DNA is made up of nucleotides Which contain: - a phosphate group - a sugar (deoxyribose) - a nitrogenous base

  8. Structure of DNA

  9. RNA • Involved in protein synthesis • Made up of nucleotides: • Nitrogenous bases (RNA only has A, U, C, G there is no T!) • A phosphate group • A sugar (ribose)

  10. Types of RNA • There are three main types: • Messenger RNA (mRNA) • Transfer RNA (tRNA) • Ribosomal RNA (rRNA)

  11. mRNA • Messenger RNA (mRNA)carries copies of instructions for assembling amino acids into proteins.

  12. rRNA • Ribosomal RNA (rRNA). • Along with proteins make up ribosomes.

  13. tRNA • During protein construction, transfer RNA (tRNA) transfers each amino acid to the ribosome.

  14. Transcription • Flow of info: DNA -> mRNA • Location: Nucleus • mRNA is produced by copying part of the DNA • The mRNA leaves the nucleus and goes into the cytoplasm and attaches to the ribosome.

  15. Transcription • Messenger RNA is transcribed in the nucleus, and then enters the cytoplasm where it attaches to a ribosome.

  16. The Genetic Code • The genetic code is read from mRNA • mRNA made off of a strand of DNA is read. • mRNA is only 4 letters A, U, C, and G • The code is read 3 letters/bases at a time • Codon= three consecutive nucleotides which are specific for an amino acid

  17. Codons

  18. Translation • Flow of info: mRNA -> Proteins • Location: Cytoplasm/Ribosomes • Translation is decoding mRNA into a polypeptide chain(protein)

  19. Step 1 Translation • mRNA attaches to a ribosome • The start codon (AUG) is located by tRNA • The matching tRNA, containing the anitcodon UAC, will bind to AUG • The tRNA carries the animo acid specific to the mRNA sequence AUG, which is methionine.

  20. Step 2 • The ribosome binds new tRNA molecules and amino acids as it moves along the mRNA.

  21. Step 3 As each new tRNA enters the ribosome, one leaves. Before tRNA can leave the ribosome, the animo acids will bond together to make a polypeptide chain

  22. Step 4 • The process continues until the ribosome reaches a stop codon.

  23. Mutations • Changes in genetic material • Many have little effect on gene expression or protein function • A few can be harmful and then some are good • Harmful mutations can cause cancer and genetic disorders • Good mutation can make altered proteins which may be beneficial in different/changing environments

  24. Point Mutations • Mutation of 1 or more nucleotides • Substitution – changing one base, usually only changes one amino acid • Insertion – addition of 1 or more bases, causes frameshifts • Deletion – removal of 1 or more bases, causes frameshifts

  25. Point Mutations

  26. Kinds of Mutations • Substitutions usually affect no more than a single amino acid.

  27. Chromosomal Mutations • Change in number or structure of a chromosome • Deletion – loss of all or part of a chromosome • Duplication – extra copies of parts of chromosomes • Inversion – reverse direction of parts of chromosomes • Translocation – chromosome breaks and attaches to another

  28. Chromosomal Mutations • Occur during Meiosis • Prophase I • Anaphase I or Anaphase II

  29. Nondisjuction • Error in meiosis in which chromosomes fail to separate.

  30. Changes to Chromosome Number • Monosomy 2n-1 • 45 chromosomes • Turners (XO) • Trisomy 2n+1 • 47 chromosomes • Down syndrome(trisomy 21), Klinefelters (XXY), Triple X (XXX), Jacobs (XYY) • Polyploidy (Triploid, Tetraploid, etc)

  31. Turners (45, XO) • 1 in 3,000 female births • Sterile females

  32. Down Syndrome • Mothers in early 20s 1 in 1,500 births • Mothers over 35 1 in 70 births • Mothers over 45 1 in 25 births

  33. Klinefelters (XXY) • 2 in 1000 male births • Sterile males

  34. Jacobs (XYY) • 1 in 1000 male births • Tall • Lower mental ability • Tendency for aggressiveness

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