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Chapter 3 Section 3 The Cell and Inheritance Walter Sutton American scientist Studied sex cells (egg and sperm) to determine how chromosomes are involved in the formation. Studied grasshoppers Sutton’s Work Grasshoppers have 24 chromosomes in body cells. Their sex cells (egg and sperm) each have 12 chromosomes. Result: egg cell + sperm cell = fertilized egg with 24 chromosomes Sutton’s Conclusion Genes are located on chromosomes Genes passed from parent to offspring on chromosomes Became known as Chromosome Theory of Inheritance Human Cells Human body cells contain 46 chromosomes (23 pairs) Sex cells (egg and sperm) contain 23 chromosomes The 23rd pair of chromosomes determines the sex of an individual. Female genotype – XX Male genotype – XY Design a Punnett Square to calculate the probability of a man and woman having a baby girl of baby boy Karyotype Definition – picture of all the chromosomes in a cell arranged in pairs Is this karyotype from a male or female? Where is there a problem? Meiosis Definition – process by which the number of chromosomes is reduced by half to form sex cells Similar to mitosis but the cell divides twice. Resulting sex cells have half the amount of chromosomes as other body cells. Meiosis vs. Mitosis Meiosis Video Clip http://www.youtube.com/watch?v=qCLmR 9-YY7o Mitosis vs. Meiosis Create a T chart to compare and contrast mitosis and meoisis for the following characteristics. Involved in what type of reproduction Type of cells which undergo the process Reason for this process to occur Stages involves (list all of the stages) Number of cells produced Number of chromosomes in the resulting cells How does resulting cell compare to the parent cell genetically? Mitosis Meiosis Reproduction Asexual Sexual Cell Type? Body cells Sex cells (Gametes) Reason? Replace old cells, add cells and growth Prepare cells for production of new offspring. Stages involved 4 stages: Prophase, Metaphase, Anaphase, Telophase 8 Stages: Prophase (I, II), Metaphase (I, II), Anaphase (I, II), Telophase (I, II), Number of cells produced 2 4 Number of chromosomes in resulting cells? Full Set (Diploid) Human = 46 Half set (haploid) Human = 23 How do daughter cells Identical DNA (clone) Different DNA – Protein Structure unwind The Genetic Code What are the 4 different nitrogen bases in a DNA molecule? How do they pair? Adenine pairs with Thymine Cytosine pairs with Guanine Base Pairing – The secret to code!! Adenine pairs with Thymine Guanine pairs with Cytocine The Genetic Code The order of nitrogen bases along a gene forms a Genetic Code that specifies what type of protein will be produced. The Genetic Code ATTCGGTG Genes make proteins Proteins make YOU!! The Genetic Code (cont.) What are the building blocks of protein? A group of three nitrogen bases codes for a specific amino acid. The production of proteins is called protein synthesis. Two steps – Transcription and Translation Introducing a new player - RNA DNA vs. RNA - Chart The Genetic Code Protein synthesis takes place on the ribosome. Two types of RNA Protein Synthesis http://highered.mcgrawhill.com/sites/0072943696/student_view0/chapter3/ animation__how_translation_works.html Mutation Definition – mistake that occurs in one gene of a chromosome. This causes the cell to produce an incorrect protein which results in a different physical trait or phenotype. Mutations Mutations are usually random and can be: Harmful – causes harm to the organism Helpful – helps the organism to survive Neither harmful or helpful. Mutations can also be caused by environmental hazards. These are usually harmful Mutations The mice ran away. Substitution Mutation Deletion Mutation Insertion Mutation The rice ran away. Thei cera naway. The migukce ran away. Steps of Protein Synthesis DNA “unzips” between the Nitrogen Base pairs Genetic info. from DNA is copied by the mRNA which leaves the nucleus and attaches to a ribosome in the cytoplasm. Steps of Protein Synthesis (cont.) Transfer RNA (tRNA) picks up amino acids according to the mRNA code of nitrogen bases. Each tRNA molecule attaches the amino acid to the growing protein chain. (Show overhead diagram and video clip) Protein Synthesis The genetic messenger is called messenger RNA (or mRNA). mRNA carries the DNA code from the nucleus out into the cell’s cytoplasm to the ribosomes where proteins are produced. This process is called TRANSCRIPTION Questions Why can’t DNA leave the nucleus to produce proteins? Why is it important for meiosis to occur? What would happen if human sex cells had 46 chromosomes instead of 23?