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Heredity-Genetics

Heredity-Genetics. A study of inheritance. Heredity vs. Genetics. Heredity: the passing of physical traits from parents to offspring Genetics: The study of heredity. History of Genetics.

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Heredity-Genetics

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  1. Heredity-Genetics A study of inheritance

  2. Heredity vs. Genetics • Heredity: the passing of physical traits from parents to offspring • Genetics: The study of heredity

  3. History of Genetics A monk named Gregor Mendel provided us with much information about the study of heredity. Gregor Mendel was born in 1822 in Austria. Mendel learned about cultivating flowers and fruit trees on his family’s farm. Mendel joined a monastery and worked in the garden where he used plants to study the way traits are passed from parents to offspring.

  4. Mendel wondered why different pea plants had different characteristics. Some grew tall while others grew short. Some had green seeds and some had yellow seeds. Each different form of a characteristic is called a trait. Mendel experimented with over 30,000 pea plants to understand the process of heredity.

  5. Garden peas were a good choice for three reasons. • They grow quickly • They are usually self-pollinating (contains both male and female reproductive structures) • They come in many varieties

  6. Mendel’s Procedure • Mendel was careful to use plants that were true breeding. A true breeding plant self pollinates and will always produce offspring with the same trait the parent plant has.

  7. Mendel’s Procedure Mendel chose to study only one characteristic at a time. Mendel chose two forms for each of the characteristics that he studied. Seed Shape: Round Wrinkled Plant Height: Tall Short Flower Color: Purple White

  8. Mendelian Genetics Throughout the years, Mendel studied a number of characteristics in pea plants including: • Height - short or TALL

  9. Mendelian Genetics Mendel studied a number of characteristics in pea plants including: • Height - short or TALL • Seed color - green or YELLOW

  10. Mendelian Genetics Mendel studied a number of characteristics in pea plants including: • Height - short or TALL • Seed color - green or YELLOW • Seed shape - wrinkled or ROUND

  11. Mendelian Genetics Mendel studied a number of characteristics in pea plants including: • Height - short or TALL • Seed color - green or YELLOW • Seed shape - wrinkled or ROUND • Seed coat color - white or GRAY

  12. Mendelian Genetics Mendel studied a number of characteristics in pea plants including: • Height - short or TALL • Seed color - green or YELLOW • Seed shape - wrinkled or ROUND • Seed coat color - white or GRAY • Pod shape - constricted or SMOOTH

  13. Mendelian Genetics Mendel studied a number of characteristics in pea plants including: • Height - short or TALL • Seed color - green or YELLOW • Seed shape - wrinkled or ROUND • Seed coat color - white or GRAY • Pod shape - constricted or SMOOTH • Pod color - yellow or GREEN

  14. Mendelian Genetics Mendel studied a number of characteristics in pea plants including: • Height - short or TALL • Seed color - green or YELLOW • Seed shape - wrinkled or ROUND • Seed coat color - white or GRAY • Pod shape - constricted or SMOOTH • Pod color - yellow or GREEN • Flower position – terminal (top) or AXIAL (sides)

  15. Mendel’s Procedure • Mendel decided to find out what would happen if he crossed two plants that had different forms of a single trait. • He used crosspollination (removing anthers from one plant and using pollen from another plant to fertilize the plant without anthers) to accomplish this.

  16. Pollination Pollination

  17. Mendel’s First Experiment Results • One trait always appeared – Dominant Trait • One trait seemed to vanish – Recessive Trait • Example: When a tall plant was crossed with a short plant – the results showed that all offspring would be tall (dominant) and none would be short (recessive) • *To find out what happened to the recessive trait Mendel decided to perform another experiment.

  18. Mendel’s Second Experiment Results • Mendel allowed the first generation from each of the 7 crosses to self-pollinate. • As a result, the recessive trait reappeared. • Example: The tall plants from the first experiment self-pollinated and produced ¾ tall plants and ¼ short plants in this generation.

  19. Even though Mendel studied 7 different traits of pea plants over the years- he was very careful to only study one trait at a time!! • Mendel reached several conclusions on the basis of his experimental results.

  20. Mendel’s Conclusions • He reasoned that individual factors must control the inheritance of traits • These factors must exist in pairs • The female parent contributes one factor while the male parent contributes the other • One factor can mask or hide the other factor

  21. Genes and Alleles Genes: the scientific word for the factors that control a trait. Genes are a section of DNA found on the chromosomes. Alleles: different forms of a trait that a gene may have. (Ex: T=tall and t=short) *An organism’s traits are controlled by the alleles it inherits from its parents.

  22. Gregor Mendel • Father of modern genetics

  23. Gregor Mendel • Father of modern genetics • Researched with pea plants

  24. Gregor Mendel • Father of modern genetics • Researched with pea plants • Studied the characteristics or traits of the pea plants to determine how the traits of offspring compare to the traits of parents.

  25. Phenotype • Phenotype • Physical characteristics

  26. Genotype • Phenotype • Physical characteristics • Genotype • Genes we inherit from our parents • Made of 2 alleles

  27. Phenotype • Facial structure Notice the similarities:

  28. Phenotype • Facial structure • Eyes Notice the similarities:

  29. Phenotype • Facial structure • Eyes • Smile Notice the similarities:

  30. Phenotype • Facial structure • Eyes • Smile • Ears Notice the similarities:

  31. Phenotype • Facial structure • Eyes • Smile • Ears • Nose Notice the similarities:

  32. Phenotype Notice the similarities: • Facial structure • Eyes • Smile • Ears • Nose • Neck

  33. Genotype The genotype is the genetic makeup of an organism. There are two types: • homozygous: an organism with two alleles for one trait that are the same (written TT or tt) This is also known as a purebred. • heterozygous: an organism with two alleles for one trait that are different (written Tt) This is also known as a hybrid.

  34. Predicting Inheritance To determine the chances of inheriting a given trait (probability), scientists use Punnett squares and symbols to represent the genes. Punnett square: can help you predict what an offspring will look like UPPERCASE letters are used to represent dominant genes. lowercase letters are used to represent recessive genes.

  35. Predicting Inheritance For example: T = represents the gene for TALL in pea plants t = represents the gene for short in pea plants So: TT & Tt both result in a TALL plant, because T is dominant over t. t is recessive. tt will result in a short plant. Remember there are two genes for every trait!

  36. Predicting Inheritance For example: T = represents the gene for TALL in pea plants t = represents the gene for short in pea plants So: TT & Tt both result in a TALL plant, because T is dominant over t. t is recessive. tt will result in a short plant. Remember there are two genes for every trait! Mendels’ Principle of Dominance Some genes (alleles) are dominant and others are recessive. The phenotype (trait) of a dominant gene will be seen when it is paired with a recessive gene.

  37. Predicting Inheritance Let’s cross a totally dominant tall plant (TT) with a short plant (tt). Each plant will give only one of its two genes to the offspring or F1 generation. TT x tt T T t t

  38. Predicting Inheritance Let’s cross a totally dominant tall plant (TT) with a short plant (tt). Each plant will give only one of its’ two genes to the offspring or F1 generation. TT x tt Mendels’ “Law” of Segregation Each gene (allele) separates from the other so that the offspring get only one gene from each parent for a given trait. T T t t

  39. Punnett Squares The genes from one parent go here. The genes from the other parent go here.

  40. Punnett Squares

  41. Punnett Squares

  42. Punnett Squares

  43. Punnett Squares

  44. Punnett Squares

  45. Punnett Squares F1 generation

  46. Interpreting the Results The genotype for all the offspring is Tt. The genotype ratio is: Tt - 4/4 The phenotype for all the offspring is tall. The phenotype ratio is: tall - 4/4

  47. Punnett Squares Your Turn!!

  48. Punnett Squares F2 generation

  49. Punnett Squares Next, give the genotype and phenotype ratios of the offspring (F2 generation).

  50. Punnett Squares Genotype ratio: TT - 1

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