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Chapter 10 Notes



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  • 1. Chapter 10 Molecular Genetics and Technology Mr. W.R. McCammon
  • 2. DNA Replication
    • Proteins control all of the process in a cell.
    • Since they are so important its vital that each protein is made exactly correct every time.
    • DNA controls the productions of every protein in a cell.
    • DNA is made up of nucleotides .
  • 3. DNA Replication
    • Nucleotides have 3 parts
      • A sugar (2 kinds)
        • Ribose (for RNA)
        • Deoxiribose (for DNA)
      • A Phosphate group
      • A nitrogen base (5 kinds)
        • Adenine is a purine
        • Thymine is a pyrimadine
        • Guanine is a purine
        • Cytosine is a pryimadine
        • Uracil replaces thymine in RNA
  • 4. DNA Replication
    • In 1953 two scientists named James Watson and Francis Crick were the first people to determine the structure of DNA
      • Two strands of nucleotides that are joined together at the nitrogen bases by hydrogen bonds.
      • Twisted ladder called a double helix. The nitrogen bases make up the “rungs” of the ladder and the phosphate and sugar units make up the sides of the ladder.
  • 5. DNA Replication
    • Chromosomes are made up DNA and proteins.
    • On chromosomes there are sections of DNA (called genes) that provide information about specific traits.
    • The sequences of the nucleotides in DNA determines the information that is passed on by the genes.
  • 6. DNA Replication
    • Steps of DNA Replication
      • The DNA unwinds and separate like an unzipping zipper (The hydrogen bonds are broken by an enzyme.)
      • Free nucleotides that are not hooked together start attaching to the unzipped DNA strand.
      • A bonds with T; C bonds with G.
      • Since DNA will contain one old strand of DNA and one new strand of DNA the process is called SEMI-CONSERVATIVE.
      • The new sugar and phosphate group combine to form the new slide of the new DNA ladder and the new nitrogen bases bond to form the new rungs of the DNA ladder.
      • DNA replication results in two identical DNA strands.
  • 7. Transcription and Translation Going from DNA to Proteins
    • RNA and DNA are different
      • RNA has a ribose sugar unit instead of the deoxiribose sugar unit.
      • DNA is double stranded and RNA is single stranded.
      • In RNA A pairs with U and not T. There is no Thymine in RNA.
  • 8. Transcription and Translation Going from DNA to Proteins
    • There are 3 different types of RNA each with different jobs:
      • Messenger RNA (mRNA) carries instruction from the DNA to the ribosomes.
      • Transfer RNA (tRNA) bring amino acids to the ribosomes.
      • Ribosomal RNA (rRNA) bind with the ribosomes to help make proteins.
  • 9. Transcription and Translation Going from DNA to Proteins
    • DNA can not leave the nucleus, therefore, the instructions have to be copied, sent to the ribosomes, and assembled there.
    • To transcribe something means to copy it. When I have you copy lines, I am having you transcribe the lines.
    • To transcribe DNA means to make a copy of it. When DNA is transcribed, a copy of the nucleotide sequence is copied by RNA.
  • 10. Transcription and Translation Going from DNA to Proteins
    • Steps of transcription
      • DNA unzips like in replication
      • Free RNA nucleotides (not DNA nucleotides like in DNA replication) pair with the nitrogen bases.
      • C binds with G; G binds with C; T (in DNA) binds with A (in RNA), but an A on the DNA strand binds with Uracil (U) on the RNA strand
      • When the base pairing is finished, the mRNA breaks away from the DNA stand, the DNA strand zips back up, the mRNA is processed, and it leaves to head for the ribosomes.
  • 11. Transcription and Translation Going from DNA to Proteins
    • Nucleotides in mRNA are in groups of 3 (called codons).
      • Each codon is the “code” for an amino acid
      • Since there are 4 bases, 64 different combinations are possible.
      • Codons code for 1 of 20 different amino acids. There are only 20 different amino acids and they make up all life on earth. This is why DNA is called the universal code.
  • 12. Transcription and Translation Going from DNA to Proteins
    • The next step when the mRNA reaches the ribosome is called translation.
      • Translation builds protins.
      • A rRNA attaches the mRNA to a ribosome and begins to “read” the nucleotide sequence
      • A tRNA will carry amino acids to the ribosome. Each rRNA has a 3 nucleotide sequence called an anticodon that will match the condons of the mRNA. If the codon is AUG then the anticodon would be UAC.
      • tRNA carries a specific amino acid to the ribosome to match the codon of the mRNA.
      • As amino acids are placed a bond forms in between the amino acids and a chain of amino acids result. There are special codons that code for “release.” They are called stop codons. They cause the polypeptide chain (protein) to be released from the ribosome.
      • The protein can either be used in a cellular process or bond with other proteins
  • 13. Transcription and Translation Going from DNA to Proteins
    • In general this process is:
    • DNA  mRNA  ribosomes  protein
  • 14. III. DNA Technology
    • Since the discovery of the structure of DNA in 1953, technology has improved and an entire new branch of science was discovered called molecular genetics.
      • The study of DNA molecules and making changes in DNA
      • A sub-field called genetic engineering which involves changing an organism’s DNA
  • 15. III. DNA Technology
    • DNA Extraction and Gel Electrophoresis
      • The first step in examining an organisms DNA is DNA extraction or removing the DNA from the rest of the cell.
      • DNA is very long and must be cut into smaller pieces to be studied.
      • DNA can be cut using restriction enzymes. Restriction enzymes cut DNA in specific sequences
  • 16. III. DNA Technology
      • Restriction enzymes are very site specific (they only will work on one nucleotide sequence) so scientists know exactly where they cut and can use whatever restriction enzyme will cut that piece of DNA they want.
      • Once cut into pieces (called fragments) the DNA is separated using gel electrophoresis.
  • 17.  
  • 18. III. DNA Technology
    • Gel Electrophoresis (con’t)
      • During gel electrophoresis the DNA containing liquid is placed into a special gel.
      • The gel is in a chamber that is connected to a power source.
      • When the power is turned on, the negatively charged DNA particles move toward the positive end of the gel.
  • 19.  
  • 20. III. DNA Technology
    • Gel Electrophoresis (con’t)
      • Smaller fragments move faster than larger ones so they travel further down the gel. These cause a pattern to be formed in the gel that can be observed.
      • These patterns can compare DNA. These patterns can be used to prove or disprove paternity , guilt or innocence of a crime, determining evolutionary history, etc
  • 21.  
  • 22. III. DNA Technology
    • Each persons DNA separates differently. When this is taken and run using gel electrophoresis a DNA fingerprint is determined.
    • DNA fingerprints are useful in crime to compare 2 DNA samples.
  • 23.  
  • 24. III. DNA Technology
    • Recombinant DNA
      • Taking short pieces of DNA from one organism and joining to the DNA of a completed different organism.
        • Once the new DNA is made it can be placed back into living cells in a process called transformation.
        • This is useful in medicine because they can transform bacteria with human DNA and have the bacteria make insulin, a human hormone that some people can not make. Lack of insulin causes one form of diabetes.
  • 25. III. DNA Technology
    • Recombinant DNA (con’t)
      • Before bacterial transformation to produce insulin people took sheep or pig injections for insulin but this caused allergic reactions in some people.
      • Now Scientists produce human insulin from bacteria using recombinant DNA and bacterial transformation.
  • 26. III. DNA Technology
    • Recombinant DNA (con’t)
      • Plasmids are small circular pieces of DNA found only in bacteria.
      • The gene for insulin is cut from a piece of human DNA and a bacterial plasmid is cut using the same restriction enzyme.
      • The DNA is combined together and placed back into a bacteria
      • The bacteria grow, reproduce and all will make human insulin.
  • 27. III. DNA Technology
    • Transgenic Organisms
      • Organisms that contain genes from a different organism .
      • Transgenic cows have extra copies of growth hormones so they grow larger and faster.
      • Transgenic plants are more resistant to disease and pests.
      • Some people think they could pollinate with wild plants and be uncontrollable or be harmful to the environment.
      • Sometimes referred to as genetic pollution.
  • 28. III. DNA Technology
    • Cloning
      • Transferring genetic material of a donor cell into an egg cell that has had its nucleus removed.
      • The egg is then stimulated to divide with the new DNA.
      • Then it’s implanted into a female for birth.
  • 29. IV. Genetic Mutations
    • Mutations are mistakes in DNA sequencing and they effect the genetic information that is passed along to the offspring.
    • Mutations can be beneficial or harmful. Most mutations are harmful and cause the death of the organisms, but some are beneficial and allow the organism to reach reproductive success.
  • 30. IV. Genetic Mutations
    • There are 2 types of mutation.
      • Gene mutations – one nucleotide is changed
        • Insertion – A nucleotide is added and changes the codons.
        • Substitution – A different nucleotide is inserted instead of the intended one.
        • Deletion – A nucleotide is left out.
  • 31.
    • Normal
    • Serine-arginine-cysteine-lysine
    • Insertion
    • Serine-arginine-leucine-stop
    • Substitution
    • Serine-arginine-phenylal-lysine
    • Deletion
    • serine-arginine-valine
    U inserted U substituted for G U is deleted
  • 32. IV. Genetic Mutations
    • There are 2 types of mutation (con’t)
      • Chromosome Mutations – The structure or number of chromosomes change
        • Deletion – A piece of chromosome is removed.
        • Duplication – Part of a chromosome is copied
        • Inversion – Pieces of chromosomes switch places.
        • Translocation – Pieces of one chromosome change places with pieces from another chromosome.
  • 33. Normal Chromosome deletion Inversion translocation A B C D E A B E A B D C E C D M F G H F G H F G H N O P Q R
  • 34. IV. Genetic Mutations
    • Karyotype – A picture of chromosomes used to see if there are abnormal numbers of chromosomes
      • Usually taken during metaphase when they are easy to see.
      • Arranged by pair, by length, and by location of centromeres.
  • 35. Karyotype
  • 36. IV. Genetic Mutations
    • Gel Electrophoresis
      • Tool used to separate DNA fragments in a gel. Shorter sections of DNA move faster and further. Shorter ones are slower.