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Chapter 11: DNA and Genes

Chapter 11: DNA and Genes. 11-1 – DNA: The Molecule of Heredity. What is DNA?. DNA ultimately determines an organism’s trait. Achieves control by producing proteins Example: Skin, muscle, bone, hair, enzymes, etc. Enzymes (protein) control the chemical reactions needed for life.

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Chapter 11: DNA and Genes

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  1. Chapter 11: DNA and Genes 11-1 – DNA: The Molecule of Heredity

  2. What is DNA? • DNA ultimately determines an organism’s trait. • Achieves control by producing proteins • Example: Skin, muscle, bone, hair, enzymes, etc. • Enzymes (protein) control the chemical reactions needed for life. • DNA contains the information – the instructions for manufacturing all proteins.

  3. The structure of DNA • DNA = Deoxyribonucleic Acid • VERY long molecule • Polymer made of repeating subunits/nucleotides. • Nucleotides have 3 parts: • Sugar – Deoxyribose • Phosphate Group • Nitrogen Base • 4 Types of Nitrogen Bases: • Adenine (A) • Cytosine (C ) • Guanine (G) • Thymine (T) • DNA Backbone – Phosphate and Sugar • Nitrogen bases stick out of the backbone like teeth on a zipper.

  4. DNA Structure Continued • Chargoff’sRule: • The amount of Adenine (A) is always found in equal amounts to Thymine (T). • The amount of Cytosine (C ) is always found in equal amounts to Guanine (G). • Forming Complementary Base Pairs. • 1953 – Watson and Crick proposed that DNA is made of 2 chains of nucleotides joined together by Nitrogen bases that are held together by a hydrogen bond (weak bond). • DNA’s shape is a double helix

  5. What about Roslind Franklin?

  6. The Importance of Nucleotide Sequences • All organisms have DNA made of the same 4 Nitrogen bases. • How can organisms be so different from each other if their genetic material is made of the same 4 nucleotides? • Different sequences of nucleotides • ATTGAC carries different information from a sequence that reads TCCAAA. • The closer the relationship between 2 organisms the greater the similarity in their order of DNA nucleotides. • Used to determine whether 2 people are related or if a blood sample matches the DNA of a suspected criminal.

  7. DNA Replication • Each cell has a copy of DNA. • DNA is in the chromosomes and is copied during DNA Replication. • Each strand of DNA serves as a pattern to make a new DNA molecule. • Step by Step: • An enzyme breaks the H bonds between N bases that are holding them together. (Unzipping the DNA) • As the DNA unzips nucleotides that are floating free in the surrounding medium (cytoplasm) bond to the open single strand of DNA by base pairing. • Another enzyme bonds to the newly made strand and “proof-reads” the nucleotides to make sure no mistakes were made. • The process continues until the entire molecule has been unzipped and replicated. • The new strand is formed and is the complement of the original “parent” DNA strand.

  8. Let’s Practice DNA Replication • ATT GAC CAT TAC AAC CGT GTA GGG AGC • TAA CTG GTA ATG TTG GCA CAT CCC TCG • TTA CGG ACC TCG ACG TAA CTC GTT AAA • AAT GCC TGG AGC TGC ATT GAG CAA TTT

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