FOB: Chapter 11

Section 11.1

DNA: The Molecule of Heredity

Vocab:
-Nucleotide
-Nitrogenous Base
-Double Helix
-DNA Replication

​I CAN...
Determine how the structure of DNA enables it to reproduce itself accurately.

• Proteins and Enzymes are essential for life​!

• Structure of DNA contains complete instructions for manufacturing ALL proteins.

What is DNA?

• DNA is a polymer with repeating subunits called nucleotides.

• Nucleotides:

  • Simple Sugar

  • Phosphate Group

  • Nitrogenous Base

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Nucleotide Structure

• Simple Sugar = Deoxyribose

• Phosphate Group = 1 Phosphorus surrounded by 4 Oxygen atoms

• Nitrogenous Base = A (adenine), T (thymine), C (cytosine), or G (guanine)

• DNA is made of 2 chains of nucleotides held together by nitrogenous bases.

• Just as teeth of a zipper hold the two sides of the zipper together, the nitrogenous bases of the two nucleotides hold the two strands of DNA together with weak HYDROGEN BONDS.

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• Always equal amounts of C & G or equal amounts of A & T

• 2 strands twisted together = double helix

• Sequence forms unique genetic info

• A-T-T-G-A-C is different from

  T-A-T-A-C-G

• 6 letter word spelled two ways; same letters different meaning.

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Importance of Nucleotide Sequence

• A cell divides by either Mitosis or Meiosis, but FIRST it must make a copy of its chromosomes.

• DNA in the chromosomes is copied through DNA replication.

• 2 molecules are formed, each strand has 1 original strand (blue) and one newly synthesized strand (pink)

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Replication of DNA

• An enzyme breaks the hydrogen bonds between bases that hold the two DNA strands together

  • Unzipping

• As DNA unzips, free floating nucleotides attach to their base pair by H⁺ bonds.

  • Another enzyme bonds these nucleotides into a chain

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​How DNA Replicates

• Process continues until entire molecule has been unzipped and replicated.

• Each new strand is a complement of one of the original, or parent, strands.

• Result = 2 DNA molecules, each of which is identical to the original DNA molecule.

  • Genetic info can then be passed on through Mitosis or Meiosis.