DNA & Genes CHAPTER 11 relating the structure of DNA to its function the role of DNA in protein production distinguish amongst different types of mutations.

DNA Molecule of Life Proteins are important components of living cells. Metabolism of cells is controlled by proteins called enzymes. Proteins are essential for life. Every cell is capable of making all the thousands of different kinds of proteins it may need.

Modern Genetics DNA of the chromosomes is the genetic material that is passed from generation to generation. Genes are sections of DNA. DNA controls cellular activities by controlling the production of enzymes.

Think On This… How does the cell synthesize proteins? What determines the kinds of enzymes present in each cell?

The molecule that controls the production of proteins is a nucleic acid called Deoxyribonucleic Acid (DNA). DNA is found in the chromosomes in the nucleus. DNA carries information for running the cell. DNA is made of nucleotides.

DNA is made up of nucleotides DNA Structure DNA is made up of nucleotides Nucleotides Have Three Parts Simple Sugar (5-carbon sugar) Phosphate group Nitrogen Base

Looking at the Structure of DNA In 1953 Watson and Crick solved the puzzle (p. 290 Fig. 11:3) These two scientists viewed x-ray images of DNA crystals that were created by Rosalind Franklin and Maurice Wilkins. DNA Structure Resembles a ladder sides: sugar and phosphate rungs (steps): complementary pairs of nitrogen bases

The structure (shape) of the DNA is referred to as a double helix.

DNA Bases In DNA, there are four possible nitrogen bases: adenine (A) guanine (G) cytosine (C) thymine (T)

4 Possible Nitrogen Bases Purines Adenine (A) Guanine (G) Pyrimidines Thymine (T) Cytosine (C) Base Pair Rule Adenine (A) to Thymine (T) And Guanine (G) to Cytosine (C)

DNA Replication

Replication of DNA DNA molecules can build an exact copy of itself. This is called Replication. (ATP is the energy source) Replication is important for reproduction and must occur every time a cell divides. That way each cell has a complete set of instructions for making proteins.

: Protein Synthesis REMEMBER: DNA is in the Nucleus Proteins are synthesized in the Ribosomes “ How can the information get to the ribosomes?” By coping a near message >>mRNA (messenger RNA) The process of transferring the information from DNA to RNA is called transcription

Transferring the info…. To carry the genetic message from the nucleus into the cytoplasm we have mRNA. Any RNA strand is a direct order from the DNA.

RNA Structure (looks like one half of a zipper) The Sugar is Ribose Single Strand Bases are: Adenine (A) to Uracil (U) Guanine (G) to Cytosine (C) **Thymine is NOT found in RNA ** Thymine is substituted with Uracil

3 Types of RNA mRNA (messenger RNA) *Carries genetic information from nucleus to ribosomes. rRNA (ribosomal RNA) *Found in ribosomes *binds to mRNA and uses instructions to assemble the amino acids in the correct order tRNA (transfer RNA) * Found in the cytoplasm * Carries amino acids in the cytoplasm to the ribosomes

DNA….to Proteins DNA Replicates….mRNA carries message to the Ribosome…

The Genetic Code EXAMPLE There are 4 bases There are 20 different kinds of amino acids in cells (A.A. are the building blocks of proteins) The groups of three bases (3 letter code) in mRNA are called codons or triplets. AUA, Codon Or Triplet EXAMPLE UUU, Codon Or triplet ACG, Codon Or Triplet

The Genetic Code Each codon codes for a particular A.A. Each codon always codes for the same A.A The sequence can be different…this gives rise to different proteins. There are 64 possible 3 letter code words. Only 20 common A.A. Some codons do not code for A.A., they provide instructions for making the proteins Example: UAA (is a stop codon) this indicates that the protein ends at this point Example:AUG (is a start codon and codes for an A.A.)

TRANSLATION (see p. 294) Bonding A. A. to form proteins is called Translation (from mRNA to Protein) tRNA: * Is shaped like a cloverleaf (Fig. 11:8) *one end has an attached site for an A.A. * the other end has an exposed base triplet called and anticodon

Information is decoded Translation: Information is decoded * If a codon (3 bases on mRNA) is AUC …..then Its’ anticodon (3 bases on tRNA) is UAG *In the cytoplasm are the A. A. necessary for building proteins. tRNA will carry the proper A.A. to the mRNA and line them in the correct order. * Once the RNA attaches to its’ specific A.A. the combination moves toward a ribosome (protein factory)

Transfer RNA (tRNA) (p. 293) Three base anticodon

Amino Acid Codons

Effects of Mutation: (p. 298) Genetic Changes (11:3) Mutation: any change in the DNA sequence. Mutagen: any agent that can cause a change in DNA…(radiation, chemicals, and even high temperatures. Effects of Mutation: (p. 298) Point mutation: Change in a single base pair in DNA Frameshift Mutation: A single base is added or deleted from DNA

Four Kinds of Chromosomal Mutations (see.p. 300) Deletion: part of the chromosome is left out Insertion: part of the a chromatid breaks off and attaches to its sister chromatid Inversion: part of a chromosome breaks off and reattaches backwards Translocation: part of one chromosome breaks off and is added to a different chromosome