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DNA NOTES

DNA NOTES. DNA STRUCTURE. DNA is constructed of three parts A sugar molecule called deoxyribose A phosphate group Nitrogen containing base 4 nitrogen containing bases are Adenine – A Guanine – G Cytosine – C Thymine - T. DNA STRUCTURE.

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DNA NOTES

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  1. DNA NOTES

  2. DNA STRUCTURE • DNA is constructed of three parts • A sugar molecule called deoxyribose • A phosphate group • Nitrogen containing base • 4 nitrogen containing bases are • Adenine – A • Guanine – G • Cytosine – C • Thymine - T

  3. DNA STRUCTURE • The four nitrogen containing bases are divided up into 2 groups • Purines: Adenine and Guanine • Pyrimidines: Thymine and Cytosine

  4. The Double Helix • In 1953, Watson and Crick created a model for the DNA molecule. The proposed model was 2 nucleotide chains that are wrapped like a spiral staircase. • This spiral staircase eventually became known as the double helix.

  5. The Double Helix • Rosalind Franklin was the person who used x-rays to look at DNA. • Watson and Crick then used her x-rays to see the spiral shape of the DNA.

  6. The Double Helix • The reason that the DNA molecule is twisted is because the molecules consist of complimentary pairs. • These pairs are pairs of nucleotide bases • Thymine always pairs with adenine • Cytosine always pairs with guanine • However in RNA there is no thymine instead adenine will pair with uracil. • The staircase is caused by the random order of the pairing and length of each molecule.

  7. DNA Replication • Before a cell can divide, it must replicate. • DNA replication begins when a section of the double helix unzips down the middle, exposing the nucleotide bases. • An enzyme called DNA polymerase moves along the two strands, pairing complimentary bases to the exposed nucleotides.

  8. DNA Replication • A complementary strand is formed for each strand of the original double helix. • DNA replication takes place at many places along the double helix and not at just one spot.

  9. DNA Replication

  10. Accuracy and Repair • The process of replication is highly accurate. There is about one error in 10,000 nucleotides. • A change in the nucleotide sequence is called a mutation. A mutation could be harmless or seriously harm a cell.

  11. RNA • The sugar molecule of RNA is ribose. • In RNA thymine is replaced by uracil, but still still pairs with adenine. • There are three types of RNA • Messenger RNA (mRNA) • Transfer RNA (tRNA) • Ribosomal RNA (rRNA)

  12. Messenger RNA • Consists of RNA molecules in a single uncoiled chain. • Carries genetic information from the DNA in the nucleus to the cytosol of an eukaryotic cell.

  13. Transfer RNA • Consists of a single chain of about 80 RNA nucleotides folded into a hairpin shape that binds to a specific amino acids • There are 45 varieties of tRNA

  14. Ribosomal RNA • rRNA is the most abundant form of RNA • rRNA consists of RNA nucleotides in a globular form.

  15. Transcription • What is transcription?

  16. Transcription • Give me some examples of where you would find transcription? • Why is transcription useful?

  17. Transcription • How would transcription be useful in DNA?

  18. Transcription • The process by which genetic information is transcribed from DNA to RNA • RNA polymerase is the enzyme used in transcription. • RNA polymerase starts transcription by binding to promoters. • It then adds a complementary pair to the chain.

  19. Translation • What is translation?

  20. Translation • Give me some examples of where translation would be found. • How is translation used in DNA?

  21. Translation • Translation takes place in the cytoplasm. • tRNA molecules and ribosomes help in the synthesis of proteins. • Translation begins when the mRNA leaves the nucleus and enters the cytoplasm. • The mRNA start codon AUG begins the protein chain.

  22. Translation • The mRNA and tRNA bind together allowing the process of translation to begin. • The binding between the two molecules continues until there is a stop codon reached. • During this time there is a long chain of amino acids created.

  23. Genetic Code • The correlation between a nucleotide sequence and amino acid sequence is called the genetic code. • The genetic information necessary for making proteins is encoded in a series of 3 mRNA nucleotides. Each combination of 3 nucleotides is called a codon. • There are a total of 64 codon sequences.

  24. CODON

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