GENE EXPRESSION Individuality & Mutations
I. Are all genes turned on in all cells? The answer is NO! Every body cell contains your DNA (genetic make-up) Cells use only genes specific for function EX. Red blood cells use only genes that make it carry oxygen Can you list more examples of proteins made? Enzymes, insulin, cell membrane, hair, muscles
**THEREFORE, NOT ALL DNA IS EXPRESSED (MADE INTO PROTEIN) IN EVERY CELL!**
Turning genes on video (5 min): http://www.teachersdomain.org/reso urce/novat10.sci.life.evo.fruitfly/ 4 This video segment investigates why one species of fruit fly has wing spots while another genetically similar one does not. As the video explains, although two organisms may both possess the same gene linked to a particular trait, this trait may not be expressed unless the gene is turned on
II. Review: Determining Sex Human Chromosomes 46 in a normal human cell! Two types: a) Normal chromosomes: 44 in each BODY CELL; 22 in each GAMETE (sex cell) b) Sex chromosomes: 2 in each BODY CELL; 1 in each GAMETE (sex cell) MALE: X and Y FEMALE: X and X
Karyotype Is this a male or a female??
Chances for having a boy or girl? 50% OF COURSE LET S SEE! X Y X XX XY X XX XY
DNA fails to copy accurately http://www.brainpop.com/science/cellula rlifeandgenetics/geneticmutatio (2:33)ns
III. Mutations: What happens when DNA goes wrong A change in the genetic material which effect genetic information and traits Not all mutations are bad, some are beneficial Ultimate source of genetic variation (depends on environment) MUTATIONS MUST OCCUR IN SEX CELLS IN ORDER FOR THEM TO BE PASSED ON TO NEXT GENERATION!!!!!!!!!! When do mutations occur? During replication (meiosis / mitosis) and protein synthesis
Mutations caused by Mutagenic Agents: 1. Radiation x- rays, UV, radioactive substances 2. Chemicals formaldehyde, benzene, asbestos fibers, nicotine
A. Chromosomal Mutations Change in number of chromosomes or structure Ex: normal human body cell = 46 Human Karyotype Arrangement of a male
Types of Chromosomal Mutations 1. Deletion A portion of a chromosome is taken away form a chromosome 2. Duplication A portion of one chromosome breaks off and is attached to its homologous chromosome giving it an extra copy 3. Inversion A portion of a chromosome breaks off and then becomes reattached to the same chromosome in an inverted (upside down) fashion 4. Translocation transfer of one section of a chromosome
Genetic Disorders Relating to chromosomal mutations Down Syndrome Due to nondisjunction failure of homologous chromosomes to separate during meiosis An extra chromosome 21
Klinefelter Syndrome XXY abnormal sexual development and infertility
B. Gene Mutations A random change in DNA sequence **Review** What does DNA ultimately code for? Proteins!!! Is construction of protein based on original DNA strand? Yes! (b/c it is what codes for mrna) What would happen to the protein if DNA sequence was changed? Wrong protein made Wrong shape of protein This would make protein unusable DNA MUTATION VIDEO http://www.bing.com/videos/search?q=mutation+videos&form=vire6#v iew=detail&mid=0f73b8e85ce1098084470f73b8e85ce109808447
Types of Gene Mutations A. POINT MUTATION: affects 1 nucelotide (base) Example: CTC on DNA makes mrna = GAG codes for GLUTAMINE If T changed to A, would have GUG which codes for VALINE Wrong AMINO ACID is coded for which means, wrong PROTEIN is made
B. FRAME-SHIFT: A base is deleted or added Example: TCA-TTT on DNA; mrna = AGU-AAA on codes for Serine + Lysine If the T is deleted in the DNA, the mrna would now read GUA-AA rrna will CODE GUA first which is for Valine 1. Similar if a base is added 2. Wrong AMINO ACID is coded for = wrong PROTEIN is made OR Translation will abruptly STOP
Disorders from Gene Mutations Sickle cell anemia Sickle shaped cells get caught in capillaries (can t transport oxygen sufficiently) Normal red blood cells (top) and sickle cells (bottom) Cystic Fibrosis- affects recessive allele mutating the CFTR gene
IV. Environmental Expression Some genes are turned on under certain environmental conditions. EX. Himalayan Rabbit: Fur changes color due to TEMPERATURE change WARM = White fur (no pigment produced) COLD = Black fur Why does this make sense? Because black absorbs the heat, helping little bunny rabbit to stay warm
V. The Human Genome How do we know that traits and diseases are genetically related? THE HUMAN GENOME PROJECT What is it? Project to identify the location of 30,000 genes Why do it? To identify the locations of genetic diseases and possibly control and/or eliminate them How far along are we? The map was completed in 2004
Class and/or Homework: Topic 3 RB pages 50-52 Read these pages and answer questions 23-31 on loose leaf paper
Topic 3 RB pgs 50-52 23) 4 24)a gene mutation is a change in the instructions of the gene. The nitrogenous bases forms the code instructions, so changing this sequence would alter the amino acid/protein 25) 3 26) 2 27) 4 28) 1 29) 1 30) 4 31) 1