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DNA

DNA. DNA (Deoxyribonucleic acid) is a long polymer of repeating units. The monomers are called nucleotides. Each nucleotide has three components: A phosphate group A ring-shaped sugar, known as deoxyribose . A nitrogen-containing base. One molecule of DNA contains billions of nucleotides.

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DNA

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  1. DNA

  2. DNA (Deoxyribonucleic acid) is a long polymer of repeating units. • The monomers are called nucleotides. • Each nucleotide has three components: • A phosphate group • A ring-shaped sugar, known as deoxyribose. • A nitrogen-containing base

  3. One molecule of DNA contains billions of nucleotides. • However, there are only four nucleotides that make up DNA. • The four nucleotides are: • Cytosine • Guanine • Thymine • Adenine

  4. PYRMIDINES PURINES • Thymine & Cytosine • Single-ring structures • Cytosine pairs with guanine • Adenine & Guanine • Double-ring structures • Adenine pairs with thymine

  5. In a single strand of DNA, nucleotides join together through covalent bonds. • The sugar base of one nucleotide bonds to the phosphate group of another nucleotide.

  6. Double Helix • DNA forms a twisted staircase when the covalent bonds form. • The structure of DNA is a double helix; meaning that the DNA is double stranded, with the two strands wrapping around each other.

  7. The bases of each strand pair together through hydrogen bonds. • A and T form two hydrogen bonds, while G and C form three hydrogen bonds.

  8. DNA Replication • Replication ensures that every cell has a complete set of identical genetic information. • A single strand of DNA serves as a template to make another identical copy.

  9. Proteins and enzymes do all the actual work of replication. • Enzymes begin the process by unwinding the double strands of DNA. • Specific proteins hold the DNA strands apart while each strand serves as a template. • Free floating nucleotides in the nucleus can pair up with the existing strands. • DNA polymerases bond the new nucleotides with the old strands.

  10. The result is two new strands of genetically identical DNA

  11. Fast & Accurate • DNA replication occurs very quickly and accurately. In humans, about 50 nucleotides are added every second. • Replication proceeds from hundreds of origins of replications along a chromosome. • DNA polymerases are also able to detect errors, take out the incorrect nucleotide and replace it with the proper one.

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