DNA - Transcription, Translation, and Mutations

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DNA - Transcription, Translation, and Mutations
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DNA

• Two strands coiled called a double helix
• Sides made of a pentose sugar Deoxyribose bonded
  to phosphate (PO4) groups by phosphodiester bonds
• Center made of nitrogen bases bonded together by
  weak hydrogen bonds

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DNA Double Helix

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Antiparallel Strands

• One strand of DNA goes from 5 to 3 (sugars)
• The other strand is opposite in direction going
  3 to 5 (sugars)

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DNA

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Synthesis Phase (S phase)

• S phase during interphase of the cell cycle
• Nucleus of eukaryotes

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DNA Replication

• Begins at Origins of Replication
• Two strands open forming Replication Forks
  (Y-shaped region)
• New strands grow at the forks

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Proofreading New DNA

• DNA polymerase initially makes about 1 in 10,000
  base pairing errors
• Enzymes proofread and correct these mistakes
• The new error rate for DNA that has been
  proofread is 1 in 1 billion base pairing errors

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DNA Damage Repair

• Chemicals ultraviolet radiation damage the DNA
  in our body cells
• Cells must continuously repair DAMAGED DNA
• Excision repair occurs when any of over 50 repair
  enzymes remove damaged parts of DNA
• DNA polymerase and DNA ligase replace and bond
  the new nucleotides together

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DNA, RNA, and Protein
The Code

• Experiments during the 1960s demonstrated that
  the DNA code was a three-base code.

• The three-base code in DNA or mRNA is called a
  codon.

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Central Dogma

• DNA is copied as RNA Transcription
• RNA uses U instead of T
• RNA is read to make proteins Translation
• Read by using the reverse of RNA, similar to
  DNAs 2nd strand

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DNA, RNA, and Protein
Translation

• In translation, tRNA molecules act as the
  interpreters of the mRNA codon sequence.

• At the middle of the folded strand, there is a
  three-base coding sequence called the anticodon.

• Each anticodon is complementary to a codon on the
  mRNA.

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Activity

• The first number tells you where the mutation
  starts, followed by the number or what is deleted
• Ex 487del7 means starting at base 487 7 bases
  are deleted.

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What Are Mutations?

• Changes in the nucleotide sequence of DNA
• May occur in somatic cells (arent passed to
  offspring)
• May occur in gametes (eggs sperm) and be passed
  to offspring

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Chromosome Mutations

• Five types exist
• Deletion
• Inversion
• Translocation (dont worry)
• Nondisjunction (dont worry)
• Duplication

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Deletion

• Due to breakage
• A piece of a chromosome is lost

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Inversion

• Chromosome segment breaks off
• Segment flips around backwards
• Segment reattaches

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Duplication

• Occurs when a gene sequence is repeated