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Transcript
9. Genetics Living Environment Mr. Wiley 144 Genetics • Genetics- the study of heredity • Heredity- passing of traits from parent to offspring • Trait- Gregor Medel (1820-1884) • Known as the father of modern genetics • Poor farming family, father hurt and lost job • Became Austrian Monk • Worked with pea plants • Work was not accepted until the early 1900’s • Some people claimed that his work was too perfect to be true. Breaking down DNA • Gene- a piece of DNA that has instructions for specific proteins • Allele- different forms of a gene Ex: Gene for blue eyes vs gene for brown eyes We get 2 alleles of each gene, why? Using the picture and your knowledge of biology answer the question about size and number of each molecule. Genotype vs. Phenotype Genotype- genetic make up of an organism Phenotype- physical appearance of an organism • Genotype determines phenotype Dominant vs Recessive What does it mean to be dominant? • Dominant- powerful traits that you always see in an organism • Recessive- less powerful traits that don’t always show themselves Ok break time, stand up! Lets find out if we are dominant or recessive. Hair Color • If you have NATURALLY dark hair (brown/black) stand on of the room If you have naturally light hair (blonde/red) stand on of the room Which one is dominant? Hair: Curly or Straight • If you have NATURALLY straight hair stand on of the room If you have Naturally curly hair of the room Which one is dominant? Eye Color • If you have dark eyes (brown/hazel) stand on of the room If you have light eyes (blue/green) stand on of the room Which one is dominant? Widow’s peak • If you have a widow’s peak stand on of the room If you do not have a widow’s peak stand on of the room Which one is dominant? Dimples • If you have a dimples stand on of the room If you do not have dimples stand on of the room Which one is dominant? Freckles • If you have freckles stand on of the room If you do not have freckles stand on of the room Which one is dominant? Earlobes: Attached or Unattached • If you have unattached earlobes stand on of the room If you do not have attached earlobes stand on of the room Which one is dominant? Can you roll your tongue? • If you can not roll your tongue stand on of the room If you can roll your tongue stand on of the room Which one is dominant? Left hand vs Right hand? • If you are right handed stand on of the room If you are left handed stand on of the room Which one is dominant? Number of Fingers • If you have 5 fingers per hand stand on of the room If you have 6 fingers per hand stand on of the room Which one is dominant? Were you dominant for every trait? No one is TOTALLY dominant or TOTALLY recessive, this phenomena is called Independent Assortment Independent Assortment – genes for different traits are inherited independent of each other. Possible Genotypes for each trait • Homozygous Dominant- receive dominant allele from both parents • Homozygous Recessive- receive recessive allele from both parents • Heterozygous- receive a dominant allele from one parent and a recessive allele from the other parent Dominant Recessive So what does this all mean? How do we use it? • Reginald Punnett • Organized Gregor Medel’s work to make it easier to understand. • Punnett Squares • Help us figure out the possible phenotype of offspring Setting up Punnett Squares B b b B • Dominant alleles – Capital letter Recessive alleles – Lowercase letter • Place alleles from parent 1 on the top (Homozygous Dominant) • Place alleles from parent 2 on the left side (Homozygous Recessive) Brown Eyes (Dominant) – B Blue eyes (Recessive) – b What percentage is each box worth? _________ Setting up Punnett Squares B b b Bb Bb B Bb Bb Brown Eyes (Dominant) – B Blue eyes (Recessive) – b What % of these offspring will have brown eyes? _______ What % of these offspring will be homozygous? ________ What % of these offspring will be heterozygous? _______ What percentage is each box worth? 25% Let’s try another one together In the wizarding world of Harry Potter, it is dominant to have magical powers and recessive to have no magical ability at all. Therefore, magical power gene is represented by the letter M, while no magical ability is represented by the letter m. Harry’s mother, Lily, is heterozygous for magical powers and his father, James, is homozygous dominant. Let’s try another one together What percentage of James and Lily’s offspring will have magical powers? ______ What percentage of James and Lily’s offspring are homozygous? _______ What percentage of James and Lily’s offspring are heterozygous? _______ Based on this information, is Harry homozygous dominant or heterozygous? Determining Phenotype • Phenotype is influenced by two major factors: Genotype AND the environment so, Genes (DNA) + Environmental factors = How you look (Phenotype) • Ex: Sunflower A sunflower can have the genes to be tall, but if its environment does not provide it with sunlight and water, it will not grow. Genes and the Environment Some mammals change their coats during winter. When the climate cools and day light gets shorter a special hormone is produced. Arctic Hare Arctic Fox This hormone triggers the animal's genes to produce more or less pigment. Summary of Mendel's Principles 1. Characteristics (traits) come from genes 2. Genes are passed from parents to offspring 3. Each adult organism has two alleles for each trait 4. Genes may be dominant or recessive 5. Alleles are independent from each other Other important principles 6. Multiple genes can control one trait 7. Phenotype is impacted by genes AND the environment Most of the hereditary information that determines the traits of an organism is located in: a)Certain genes in the vacuole of body cells b)The nucleus of body cells of that individual c) Only those cells of an individual produced by meiosis d)The number of ribosomes in certain cells A child has brown hair and brown eyes. His father has brown hair and blue eyes. His mother has red hair and brown eyes. The best explanation for the child having brown hair and brown eyes is that: a) a gene mutation occurred that resulted in brown hair and brown eyes b) gene expression must change in each generation so evolution can occur c) the child received genetic information from each parent d) cells from the mother’s eyes were present in the fertilized egg. During the warm temperatures of summer, the arctic fox produces enzymes that cause its fur to become reddish brown. During the cold temperatures of winter, these enzymes do not function. As a result, the fox has a white coat that blends into the snowy background. This change in fur color shows that a) the genes of a fox are made of unstable DNA b) mutations can be caused by temperature extremes c) random alteration of DNA can occur on certain chromosomes d) the expression of certain genes is affected by temperature In giraffes, the gene for neck length is denoted by the letter “N.” It is dominant to have a long neck. If you went to the zoo and saw a heterozygous giraffe, what is its phenotype? If that giraffe mates with a pure short neck giraffe, what are all of the possible genotypes and phenotypes of the baby giraffes?
