Chapter 12 DNA The Molecule of Heredity DNA

Chapter 12 DNA: The Molecule of Heredity

DNA n Deoxyribonucleic acid (Genes) is found in nucleus. Rosalind Franklin produced X-ray diffraction pictures of DNA. Wilkins (Her lab partner) shared Franklin's data, without her knowledge, with Watson and Crick, at Cambridge University, ultimately publishing the proposed structure of DNA in March 1953. Watson & Crick were given credit for discovering the DNA structure. The 1962 Nobel Prize was awarded to Maruice Wilkins, Francis Crick, and James Watson for the discovery of DNA's double helix.

DNA • All organisms contain DNA made up of nucleotides • DNA determines an organism’s traits & direct protein production • Enzymes are proteins that control all chemical reactions of an organism

n DNA is arranged in a double helix (twisted ladder) n DNA is a polymer made up nucleotides n Nucleotides are made up of 1. 2. 3. nitrogen base phosphate simple sugar

DNA G C A T Purines 2 loops A&G Pyrimidines 1 loop T&C

n The backbone (sides) of the ladder is made up of deoxyribose sugar and phosphoric acid (phosphate). n There are four nitrogen bases ATGC Complementary base pairs Adenine - Thymine Guanine - Cytosine These bases are held together by hydrogen bonds

DNA Replication n DNA is replicated during interphase n An enzyme breaks the hydrogen bonds between the nitrogen bases n (Untwist the DNA molecule, unzipping bonds) n Free nucleotides are bonded to original strand by a different enzyme Replication 1 Cell - 2 DNA 4 DNA 2 cells 2 DNA

DNA Replication Results in… n two identical strands of DNA n Each ½ the original (or parent nucleotides) and ½ a complementary (or new nucleotides).

DNA vs. RNA DNA RNA 2 1 Type of Sugar Deoxyribose Ribose Type of Bases ATCG AUCG Uracil # of Strands

11. 2 From DNA to Protein Ribonucleic acid - used to get the genetic code from DNA translated into a Protein

DNA to Protein

From DNA to RNA - Transcription n In the nucleus, enzymes make an RNA copy of a portion of a DNA strand. n This results in a single strand of m. RNA

From DNA to RNA n m. RNA (messenger RNA) carries this copy of the code for making proteins out into the cytoplasm to the ribosomes. n Ribosomes are made partly of ribosomal RNA ( r. RNA)

From DNA to RNA - translation n The m. RNA attaches to the Ribosome. n Transfer (t. RNA) Translates the code on the m. RNA by using an Anticodon. n The anticodon matches the codon and brings the correct Amino Acid.

From DNA to RNA – protein synthesis n The amino acids bond together with peptide bonds and form a protein n The proteins form anything from digestive juices to muscles

RNA CODE = CODONS n DNA codes for 20 amino acids (AA) that make up all of our proteins. n 3 nitrogen bases (called the codon) represent one amino acid n 61 of the 64 triplet codes represent the 20 amino acids. n Some codons are start and stop codons n Genetic code is universal (at least every living thing we know of).

Codons are how the RNA Makes Proteins

Amino Acid Chart of Codons

The Decoder Ring

DNA to Protein

Mutationsmistakes or changes in genetic material n Gene mutations- changes in one or more nucleotides n Chromosomal mutations- changes in number or structure of chromosomes n Sex cell mutations result in the entire offspring with that change in code n Body cell mutation affects that body part n Many, if not most, mutations are neutral, meaning that they have little or no effect

Gene Mutations 1. Normal Code THE CAT ATE THE RAT Point mutation n Frame shift n Mutation n n THE CAP ATE THE RAT THE CA-A TET HER AT THE CAR TAT ETH ERA T THE EHT ETA TAC RAT Substitution Deletion Insertion Inversion 2. 3. THE CAT ATE THE RAT HER BAT ATE THE BUG n HER BAT ATE THE RAT Translocation

Chromosomal Mutations Nondisjunction – the tetrads fail to disconnect during anaphase I of Meiosis • Polyploidy is a condition in which an organism has extra sets of chromosomes

12 -4 Mutations n 12– 4 Mutations

Gene Regulation Operon- a group of genes that operate together as a functioning unit of DNA including: • an operator • a common promoter • and one or more structural genes,

Gene Expression

RNA Editing Many eukaryotic genes have a sequence called the TATA box that helps position the polymerase just ahead of the sequences of nucleotides transcribed into m. RNA When RNA molecules are formed, introns and exons are copied from DNA. • introns are not involved in coding for proteins • exons are the DNA sequences that code for proteins are called.

RNA splicing

Development and Differentiation n As cells grow and divide, they undergo differentiation, meaning they become specialized in structure and function. n Hox genes control the differentiation of cells and tissues in the embryo.