Remember the central dogma… Cytoplasm Ribosome Nucleus Translation
Central Dogma Genetic information travels from DNA RNA Protein (made of amino acids) The sequences of amino acids in proteins is determined by base pairs in the DNA
Review What happens to the two DNA strands before replicating? They separate How is DNA replication different in prokaryotes vs. eukaryotes? Prokaryotes no nucleus, one starting point; eukaryotes occurs in nucleus, may different starting points What two processes would replication occur before? Mitosis or Meiosis
Review What process involves swapping of DNA between homologous chromosomes? Crossing Over During what cell process does this occur? Meiosis What controls the sequence of amino acids in protein? DNA sequences containing genes What carries messages from DNA to ribosomes? RNA
AIM: How do changes in DNA affect genes?
What are mutations? Cells make mistakes in copying their DNA The wrong base can be inserted: T-C? It can happen in mutations A base can be skipped or not put in The mistakes in the DNA bases are called MUTATIONS
Types of mutations Point mutations – occur at one point in a DNA sequence Examples: Substitutions One base in the DNA sequence is changed to a different base A-T-T-A-G-C-G-A-T… A-T-C-A-G-C-G-A-T… T-A-A-T-C-G-C-T-A… T-A-A-T-C-G-C-T-A…
Types of mutations Point mutations – occur at one point in a DNA sequence Examples: 2. Insertions/Deletions One base is added or subtracted Alter amino acid sequence in protein – FRAMESHIFT MUTATION THESE CHANGE EVERY AMINO ACID AFTER THE MUTATION A-T- T-A- A -T-C-G-C-T-A … T -A-G-C-G-A-T… A-T-A-G-C-G-A-T-… T-A-A-T-C-G-C-T-A… INSERTIONS/DELETIONS can cause a protein to become dysfunctional because all the amino acids will be out of order…
Regents Review A change in the base sequence of DNA is known as a gene mutation a karyotype nondisjunction polyploidy
Regents Review A random change in the base sequence of DNA resulting in the production of a defective protein is called translocation addition deletion gene mutation
What causes mutations? Errors in replication Enzymes insert wrong bases about once every 10 million bases The environment - MUTAGENS Chemicals like pesticides, tobacco smoke RADIATION! X-ray, UV light (sunlight) Can be called MUTAGENIC AGENTS Radioactive Substances are very dangerous!!!!
Regents Review Although genetic mutations may occur spontaneously in organisms, the incidence of such mutations may be increased by radioactive substances in the environment lack of vitamins in the diet a long exposure to humid climates a short exposure to freezing temperatures
The effects of mutations They can have no effect Imagine an A gets deleted and another A gets inserted They can produce negative changes Maybe a mutations turns on cell division CANCER They can produce beneficial changes (yes, really) A plant can become resistant to certain bacteria POLYPLOIDY – an organism has an extra set of chromosomes Typically, this make plants larger and stronger!
Regents Review Because x-rays and ultraviolet light can change the chemical nature of DNA, they are known as mutagenic agents growth regulators hydrolytic enzymes toxic wastes
Regents Review Strontium-90, a radioactive isotope found in nuclear fallout, is incorporated and used by the human body in much the same manner as calcium. Because of its radioactive nature, strontium-90 would probably cause disjunction of chromosomes take the place of phosphorus in chromosomes act as a mutagenic agent within bone cells inhibit the development of mutations
Regents Review Mutagenic agents are substances that increase the rate of gene mutations decrease the rate of gene mutations have no effect upon the rate of gene mutation cause gene mutations but not other chromosomal changes