Genes and Gene Technology Chapter 6 Genes and Gene Technology

Genes need to do 2 things Supply instructions for cell processes and for building cell structures Must be able to be copied so that each cell contains an identical set of genes.

Nucleotides – the subunits of DNA DNA is made of only four subunits Each subunit is identical except for the base. sugar + phosphate + base Possible bases are 1) adenine 2) thymine 3) guanine 4) cytosine

Thymine Cytosine Adenine Guanine

Chargaff’s Rule In 1950, he found that the amount of adenine in DNA always equaled the amount of thymine and that the amount of guanine always equaled the amount of cytosine. # adenine = # thymine # guanine = # cytosine

Watson and Crick * Concluded that it resembles * Discovered the a twisted ladder called a double helix * Discovered the structure of DNA

DNA Double Helix

DNA Structure The two sides of the ladder are made of alternating sugar and phosphate molecules. The rungs of the ladder are composed of a pair of nucleotide bases. Adenine always pairs with Thymine Guanine always pairs with Cytosine

Making Copies of DNA Because adenine always bonds with thymine and guanine always bonds with cytosine, one side of a DNA molecule is complementary to the other side. ACCGT will always bind with TGGCA In order to copy itself the DNA must first partially unwind.

Exceptions to Mendel’s Rules In higher level organisms, like humans, Heredity is much more complicated and harder to predict than Mendel’s peas. Incomplete Dominance Codominance One gene influencing many traits Many genes influencing a single trait

The importance of environment Many things in your environment also influence how you grow and develop. Diet, exercise, exposure to dangerous chemicals or radiation. Genetic Predisposition – a higher than normal probability that a particular trait will appear. Expression of the gene is influenced by the environment. Something in the environment turns the gene on (the ?)

DNA unites all organisms DNA functions in the same way for all organisms from bacteria to mosquitoes to whales to humans. All life as we know it is governed by DNA. At the same time it is what causes each of us to be unique.

How DNA Works Each group of 3 bases codes for one amino acid The order of the bases on the DNA determines the order of amino acids on the proteins which are assembled based upon the instructions coded in the genes. Each group of 3 bases codes for one amino acid

Why Proteins Proteins exist in an almost limitless variety. The human body contains about 50,000 different proteins. Proteins are the reason for the multitude of different shapes, sizes, colors, and textures found in living things, such as antlers, claws, hair, and skin.

How the Protein is Made A copy of the section of the DNA containing the gene for a particular protein is made. Copier enzymes copy this by utilizing the complementary code. A mRNA (messenger RNA) than carries this genetic info from the nucleus out into the cytoplasm.

How the Protein is Made continued 4) The copied DNA is fed through the ribosome (acting like a factory) reading three bases at a time & constructing the protein. 5) Transfer molecules (tRNA) carry around a specific amino acid in the cytoplasm. As the DNA copy is fed through the ribosome, the appropriate tRNA links up with the bases on the DNA. This causes the tRNA to drop off the amino acid it is carrying, such that a chain of amino acids is formed in concert.

Changes in Genes Mutation – a substitution, deletion, or an insertion of an extra base into the code. Caused by random errors and mutagens. Most mistakes are corrected by repair enzymes but sometimes the code is not corrected.

3 possible outcomes of mutations An improvement No change Harmful change If the mutation occurs in the sex cells then it can be passed on from generation to generation

How can DNA be damaged Mutagen – physical or chemical agent that can cause a mutation. high energy radiation asbestos cigarette smoke

Sickle Cell Anemia One 3 base sequence (GAA) that codes for the amino acid glutamic acid if changed to (GTA) ends up coding for valine instead resulting in a human blood cell being sickle shaped instead of the normal biconcave - resulting in substantial reduction in oxygen carrying capacity.

Genetic Counseling Carriers? Why counsel? What is a Pedigree diagram?

Sickle Cell Pedigree Chart

Designer Genetics Selective genetics – organisms with desirable characteristics are mated to produce a new breed or a super organism. Genetic Engineering – manipulation of individual genes to improve an organism or to repair a problem.

Ethical, Beneficial or Not? Cloning? Genetic Engineering of Foods? Gene Therapy for Diseases? Genetic Choice for babies? Creating super animals? Creating super humans?