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Genetics

Genetics. The Science of Heredity. Construct your pet. Use the possible traits to make your pet Decorate your pet Make the chart on the back Complete the phenotypes Leave the genotypes blank. Gregor Mendel (Father of Genetics). 1951 Priest who grew hundreds of pea plants

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Genetics

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  1. Genetics The Science of Heredity

  2. Construct your pet • Use the possible traits to make your pet • Decorate your pet • Make the chart on the back • Complete the phenotypes • Leave the genotypes blank

  3. Gregor Mendel (Father of Genetics) • 1951 Priest who grew hundreds of pea plants • Wondered why some pea plants had different characteristics (tall, short, green seeds, yellow seeds)

  4. Mendel questioned the following items with pea plants • Traits - different physical characteristics • Often he noted that the pea plants had traits similar to their parents • Heredity - passing of traits from parents to offspring • For over ten years, Mendel experimented with pea plants to understand heredity • Genetics – scientific study of genetics

  5. Mendel decided to cross plants with opposite forms of a trait (short with tall) • He started with purebreds • Purebreds – one that always produces offspring with the same form of a trait as the parent • Purebred short always produce purebred short • Mendel called these plants the parental plants or P generation. • The offspring was the filial generation of the F1 generation. Filial means son.

  6. Offspring in F1 was all tall (shortness trait disappeared)F1 plants grew and self pollinatedPlants in F2 were a mix (short reappeared)

  7. Other studies of Mendel • Seed shape • Seed color • Seed coat color • Pod shape • Pod color • Flower position • Same results occurred. Only one form of the trait appeared in F1 but in F2 the lost trait reappeared in ¼ of the plants.

  8. He determined • Individual factors control the inheritance of traits in peas • Female parent contributes one factor • Male parent contributes the other factor • Theses factors are called genes and alleles

  9. Genes- factors that control traits • Alleles- different forms of a gene • Individual alleles control inheritance of traits. Some are dominant, others are recessive. • Dominant – trait that always shows up in the organism when the allele is present • Recessive – masked or covered up when the dominant allele is present

  10. Review of Dominant and Recessive Alleles Alleles control the inheritance of traits Two types: Dominant alleles is one whose trait shows up in the organism when the allele is present Recessive allele is hidden when the dominant allele is present

  11. The F1 plants are hybrids • Purebred pea plants • two alleles for tall stems • Two alleles for short stems • F1 generation • One allele for tall stems from tall parent • One allele for short stems from the short parent • Hybrids – have two different alleles for the trait • Dominant alleles mask the recessive

  12. Review of Purebreds vs. Hybrids • Purebred is one that always produces offspring with the same form of a trait as the parent • Hybrid is one that has two different alleles for a trait.

  13. Shorthand for dominant and recessive traits • Dominant - represented by a capital letter • Recessive – represented by a lowercase letter • Tall stems – T • Short stems - t

  14. Examples of what plants inherit • Two dominant alleles • TT • One dominant allele • Tt

  15. Mendel’s work • 1866 – took work to scientific socity • Forgotten for 34 years until 1900 when discovered by 3 scientists. • Because of his work, he is known as the Father of Genetics

  16. Paper Pet Genotype • Complete the genotype of your pet • Answer questions 1 – 3 on page 91

  17. Class Survey – Part 1 • 1. Are traits controlled by dominant alleles more common than traits controlled by recessive alleles? • Write your hypothesis______________________________________________________________________________ • 2. For each of the traits listed in the data table, work with a partner to determine which trait you have. Note the traits. • 3. Count the number of students who have each trait. Record that number in your data table. Also record the total number of students.

  18. Class Survey – Part 2 • Look at the circle of traits. Place the eraser end of your pencil on the trait in the small central circle that applies to you (free or attached ear lobes). • Look at the two traits touching the space your eraser is on. Move your eraser to the next description that applies to you. Continue to trace your traits until you reach a number. Share this number with your classmates.

  19. Analyze and conclude the class survey • Answer the three questions about the survey and conclude your findings.

  20. What’s the Chance? • Pg. 94

  21. Probability & Genetics • Probability – likelihood that a particular event will occur. • The laws of probability predict what is likely to occur, not what will occur. • Probability of a coin landing on heads is 50%.

  22. Pipe Cleaner Activity • What is the chance that the longest pipe cleaner will be chosen? • ¼ • If the longest pipe cleaner is chosen the first time and is replaced what is the chance it will be chosen again?

  23. Bag of marbles • Suppose 6 out of 10 marbles are red in a bag are red. • What is the probability of choosing a red marble? • 6/10 • What if the other 4 are blue. What is the probability of blue? • 4/10 • What is the probability of green? • 0 • What is the probability you will pull a marble from the bag. • 1

  24. Mendel realized math applied to Genetics

  25. Punnett Squares • Punnett square is a chart that shows all the possible combinations of alleles that can result from a genetic cross. • The allele passed on is based on chance. • There are four possible combinations.

  26. Punnett Squares Two purebreds • Two hybrids

  27. Punnett Squares • Two purebred • One purebred and one hybrid BB BB Bb bb

  28. Try a Punnet Square for: • Hybrid and Hybrid • Two recessive traits passed from each parent.

  29. Phenotypes and genotypes • Phenotype is the visible traits • Genotype is the genetic makeup or allele combinations

  30. If a pea plant’s genotype is Tt, what is it’s phenotype?

  31. Genotypes & Phenotypesfor Pea Plant If the genotype is…. What is the phenotype? Tall Tall Short • Tt • TT • tt

  32. Homozygous is an organism that has two identical alleles for a trait • Heterozygous is an organism that has two different alleles for a trait.

  33. For all of the traits Mendal studied, one allele was dominant and the other recessive • This is not always the case • Some alleles are nether dominant or recessive. • In this case both alleles are expressed in the offspring.

  34. Codominance - where alleles are neither dominant or recessive

  35. The codominant alleles are written as capital letters with superscripts. Fb for black Fw for white

  36. Codominance in cattle – Red and White hair are codominant. Can look pinkish brown. Called roan.

  37. Construct a Punnett square for a cross between two heterozygous Erminette chickens (FbFw) that shows all the possible genotypes and phenotypes of offspring. Also calculate the probabilities of each genotype and phenotype.

  38. Fb Fw Fb FbFw FbFb FwFb FwFw Fw

  39. Complete page 99 • #1-4 • Page 81 on Probability & Genetics

  40. Make the Right Call!

  41. Make the Right Call! • Complete Analyze Questions. • Turn in the answer and make sure your name is at the top of your answers. • Put the word partner and write the name of your partner at the top as well.

  42. Walter Sutton1903 *Studied the sex cells of Grasshoppers

  43. Sutton’s grasshopper experiment Chromosomes were the key to understanding how offspring come to have traits similar to those of their parents. Genes are located on chromosomes

  44. The cell and inheritance • A sperm is the male sex cell. • Carries half of the chromosomes • In humans-23 • An egg is the female sex cell • Carries half of the chromosomes • In humans-23

  45. Chromosomes • Rod-shaped cellular structure made of chromatin. • Contains DNA • Controls inherited characteristics such as eye color and blood type • Women have two x chromosomes XX • Men have one x and one y XY

  46. meiosis • Process by which the number of chromosomes is reduced by half to form sex cells - sperm and egg

  47. 3 4 2 1 Meiosis 1 2.Each parent cell has 4 chromosomes arranged in two pairs that line up in center 3. pairs separate to opposite ends 4. 2 cells form with ½ of the chromosomes • 1. Beginning of Meiosis – chromosomes are copied

  48. Meiosis 2 5. chromosomes move to center of cell 6. chromosomes split and move to opposite ends of the cell 7. 4 sex cells have been produced. Each cell has only one chromosome from the original pair. 5 6 7

  49. During meiosis • Sex cells combine to produce offspring • Each sex cell will contribute half the normal number of chromosomes • Thus the offspring gets the normal number of chromosomes • Each human has 46 chromosomes

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