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DNA / Protein Synthesis

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Presentation on theme: "DNA / Protein Synthesis"— Presentation transcript:

1 DNA / Protein Synthesis

2 I. DNA Structure Made up of 1000s of repeating units (nucleotides)
Each nucleotide has 3 parts: phosphate, sugar (deoxyribose) and a nitrogenous base

3 I. DNA Structure DNA Nucleotides can have 4 different bases Adenine
Cytosine Guanine Thymine

4 I. DNA Structure Watson – Crick Model of DNA
2 connected chains of nucleotides Sides = phosphates and sugars held together by strong ionic bonds Rungs = N. base pairs held together by weak hydrogen bonds 2 chains are twisted in a spiral (double helix)

5 I. DNA Structure The 4 bases only bind in a certain way
Adenine – Thymine (A – T) Cytosine – Guanine (C – G) The 2 strands are complimentary (A on one and T on the other)

6 I. DNA Structure

7 II. DNA Replication DNA can copy itself with the help of enzymes
Happens during mitosis and meiosis in the nucleus of the cell Process DNA unwinds 2 strands separate between the bases Free nucleotides in cytoplasm enter nucleus and bind with complimentary bases on DNA strand Makes 2 identical DNA molecules DNA replication


9 III. Gene Control of Cell Activities
Genes for a trait (phenotypes) are determined by the DNA nucleotide sequence Genes control protein and enzyme synthesis and these control cell activities

10 III. Gene Control of Cell Activities
Example Dominant gene for production of lactase (digests the milk sugar, lactose). People who are recessive cannot make lactase, so they cannot digest lactose The sequence of DNA nucleotides determines the sequence of amino acids in enzymes and other proteins There is over 1 meter of DNA in EACH human cell

11 IV. RNA Made of nucleotides but have 3 main differences
Sugar is ribose, not deoxyribose Uracil (U) is substituted for Thymine (T) Single stranded, not double stranded

12 IV. RNA Messenger RNA (mRNA) Made in nucleus and moves to ribosome
Formation (Transcription) DNA unwinds and unzips RNA nucleotides bind w/ complementary bases on DNA strand DNA serves as a template (pattern) for the synthesis of RNA Transcription

13 IV. RNA Sequence of nucleotides in mRNA contains the genetic code which determines the sequence of aa in proteins EACH aa is represented by a SPECIFIC sequence of 3 nucleotides (codon)

14 IV. RNA Transfer RNA (tRNA) Found in cytoplasm
20 different kinds of aa in cells, w/ at least one tRNA for each Each tRNA has a 3 nucleotide sequence (anticodon) that is complimentary to the codon on the mRNA tRNA carry the specific aa to ribosome and temporarily bind to mRNA during protein synthesis

15 V. Protein Synthesis mRNA is made in nucleus from a section of DNA (gene for protein) (transcription) mRNA moves to cytoplasm and binds to ribosome aa are carried to mRNA/ribosome by tRNA Anticodons on tRNA bind w/ codons on mRNA (bringing the aa with it) aas bind together (forming PEPTIDE bonds)

16 V. Protein Synthesis Once the aa binds, the tRNA breaks away to find a new aa This continues (forming an aa chain that will eventually form a protein) until a STOP codon is reached. The STOP codon tells the ribosome to break away and release the protein Translation

17 Gene Mutations ANY change in the sequence of nucleotides in DNA
MUST happen in sex cells in order to be passed on to offspring Types Addition (AAGCCA  AAGGCCA) Deletion (AAGCCA  AGCCA) Substitution (AAGCCA  AGGCCA) Inversion (AAGCCA  ACGACA)

18 VII. Cloning Make identical offspring from parent
Inject nucleus of body cell (2n) into an egg which had the nucleus removed “Fertilized” egg is implanted into surrogate mother and new organism forms Has been achieved in plants, frogs, mice, sheep, goats, cows and monkeys


20 VIII. Genetic Engineering
Transfer of genetic material from one organism to another Process Restriction enzyme is used to cut out a piece of DNA that has a desired gene from a donor organism’s DNA

21 VIII. Genetic Engineering
The piece of DNA is placed into a circular piece of bacterial DNA (plasmid) that was cut with the same restriction enzyme The “recombined” DNA is placed into the new organism. The protein from the trait can now be made.


23 VIII. Genetic Engineering
Used to make human growth hormone and insulin Genes were placed into bacteria. Now all of the offspring have the gene (mitosis) and they make the chemical Get large low cost Plants can now contain genes to make chemicals that kill insects feeding on the plants

24 IX. Gel Electrophoresis
Used to compare DNA from different organism Procedure DNA is cut using restriction enzymes. This cuts at specific points making different sized fragments of DNA Fragments are placed into wells on one side of gel

25 IX. Gel Electrophoresis
Electricity is run through the gel causing the (-) charged DNA to the (+) end (away from the wells) Smaller fragments travel faster through gel, making them further away Gel is then stained to show the “bar” pattern for the DNA sample Gel Electrophoresis


27 IX. Gel Electrophoresis
Used for: Relating different DNA samples to each other Determining the father of a child Proving hospital mistakes (wrong child) Proving guilt / innocence in a crime Determining the genes responsible for some genetic diseases

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