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Chapter 5

Chapter 5. Heredity. Ch 5.1 - Genetics. Heredity – the passing of traits from parents to offspring 1. Genes on chromosomes control the traits that show up in an organism 2. The different forms of a trait a gene may have are alleles. The Human Genome (Project 1990-2003).

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Chapter 5

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  1. Chapter 5 Heredity

  2. Ch 5.1 - Genetics • Heredity – the passing of traits from parents to offspring 1. Genes on chromosomes control the traits that show up in an organism 2. The different forms of a trait a gene may have are alleles

  3. The Human Genome(Project 1990-2003)

  4. 3. Each sex cell contains one allele for that trait 4. The study of how traits are inherited is genetics

  5. B. Gregor Mendel – “Father of Genetcs” 1. Mendel was the first to use mathematics of probability to explain heredity and to trace one trait for several generations

  6. 2. Allele – the different variations of a trait that genes carry a) Dominant allele – covers up or dominates the other trait b) Recessive allele – the trait that doesn’t show up or seems to disappear c) Hybrid – receives different genetic information for a trait from each parent

  7. 3. Probability – helps predict what an offspring will inherit 4. Punnett square – tool to help predict what an offspring will inherit a) Uppercase letters stand for dominant alleles b) Lowercase letters stand for recessive alleles

  8. 5. Genotype – the genetic makeup of an organism (represented by the letters) a) Homozygous – an organism with 2 alleles for one trait that are the same • (TT or tt) b) Heterozygous – an organism with 2 alleles for one trait that are different • (Tt)

  9. 6. Phenotype – the way an organism looks or behaves as a result of its genotype

  10. Example: In peas, the color yellow is dominat (Y) to the color green which is recessive (y) Find the probabilities of what genes the offspring of 2 heterozygous parent plants would inherit Genotype: Phenotype:

  11. Ch 5.2 – Genetics Since Mendel A. Incomplete Dominance 1. Neither allele is dominant for a trait 2.The phenotype produced is intermediate between the 2 inherited traits

  12. Ex: four o’clocks red flowers x white flowers = pink

  13. B. Multiple Alleles 1. More than 2 alleles control a trait 2. Can produce 3 or more phenotypes

  14. Ex: Blood types Alleles – A,B, and O Phenotypes – Type A, Type B, Type AB and Type O

  15. C. Polygenic Inheritance 1. A group of genes act together to produce a trait which creates a great variety of phenotypes 2. Many human traits are controlled in this way

  16. Ex: hair color, eye color, skin color, height

  17. D. Mutations – genes that are copied incorrectly 1. Can be harmful, beneficial or have no effect 2. Chromosome disorders – caused by inheriting too many or too few chromosomes

  18. Ex: Down(‘s) Syndrome – extra copy of chromosome 21

  19. E. Recessive Genetic Disorders 1. If both parents have a recessive allele for a disorder they can pass it on to their child 2. Because the parents are heterozygous they show no symptoms themselves

  20. Ex: Cystic Fibrosis C = no cystic fibrosis c = has cystic fibrosis C c C CC Cc Cc c cc 25% chance child could inherit this disease

  21. F. Sex Determination 1. One pair of chromosomes (called X and Y chrom’s) are responsible for the sex of an organism 2. Female egg cells- carry X chromosomes Male sperm cells- half have X & half have Y

  22. 3. If two X’s are inherited: XX = female If one X and one Y are inherited: XY = male X Y 50% chance boy XX XY X 50% chance girl X XX XY

  23. G. Sex-linked Disorders – disorders that can be inherited by genes on the X or Y chromosomes Ex: color blindness

  24. Ch 5.3 – Advances in Genetics A. Genetic Engineering – changing the arrangement of DNA that makes up a gene 1. Recombinant DNA a) inserts useful DNA segment into bacteria cell b) Insulin for diabetic patients is produced in this way

  25. 2. Gene Therapy a) Inserts normal DNA into a virus which can then infect human cells and reproduce more copies of it b) Also done in plants by inserting genes with desired traits

  26. B. Pedigree – a tool used to show patterns of genetic inheritance and follow traits through a family Affected Male Unaffected Male Affected Female Unaffected Female

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