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Gene Expression

Gene Expression. From a gene to a protein. Central Dogma. (Crick 1958) Determines the genetic flow of information. Central Dogma. First step: a genetic message from DNA is to copied (transcribed) into mRNA, which contains the code for making proteins

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Gene Expression

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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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