Genetics

1. Genetics

2. Section 2: vocabulary: • 1. Genetics • 2. Allele: alternate forms of the gene • 3. Dominant : appears in the F1 • 4. Recessive: not present in the F1 • 5. Homozygous : same alleles • 6. Heterozygous : different alleles • 7. Genotype: alleles • 8. Phenotype: physical • 9. Law of segregation • 10. Hybrid • 11. Law of independent assortment

3. monohybrid cross true-breeding P generation F1 generation F2 generation Punnett square test cross probability pedigree sex-linked gene polygenic inheritance incomplete dominance multiple alleles codominance • Additional Vocabulary

4. The “Father of Genetics”! • Genetics: the science of heredity. • Gregor Mendel

5. Gregor Johann Mendel (1822 - 1884) was a member of an Augustinian order (Monastic) in Brunn Austria

6. Mendel began studying plant breading by trying to find the effects of crossing different strains of common garden pea • He carried out his research with more precision than had yet been used. He also used the new science of statistics to analyze the results of his experiments. This use of mathematics to describe biological phenomena was a new concept.

7. Gregor Mendel bred varieties of the garden pea in an attempt to understand heredity. • Mendel observed that contrasting traits appear in offspring according to simple ratios.

8. genotype • The organism’s allele pairs : what genes it has to produce the outward appearance it has.

9. Homozygous genotype • An organism with two of the same alleles for a trail. Both alleles are the same Dominant Recessive

10. Heterozygous genotype • An organism with 2 different alleles for a trait.

11. Hybrid 279 • Heterozygous genotypes

12. Phenotype • The observable or outward expression of the allele pair that an organism has… what it “looks” like.

13. Monohybrid crosses • Two parents differ by only one trait. • Height tall or short or smooth/ wrinkled Green/ yellow

14. Monohybrid traits

15. Monohybrid crosses

16. Results of a monohybrid crossfirst generation F1 • One of the characteristics would kind of “take over” the other and the offspring would all look like only one of the parents. • Example: green and yellow • All offspring were yellow!

17. Second generation F2 • When the parents from the F1 are crossed. • Yellow X Yellow = • ¾ were Yellow but ¼ was green . • The green trait reappeared!!!!

18. Mendel collected 6022 yellow peas and 2001 green. • this was almost a perfect 3:1 ratio of yellow :green • He studied several traits and each gave this ratio!

19. F2 generation

20. What did Mendel learn from this? • Each organism has two factors for each of its traits. • “Factors” are forms of the Genes on chromosomes. • These are the alleles

21. alleles • An alternative form of a single gene passed from generation to generation. • Example: the yellow or the green form of the color of peas are each alleles of the gene for the color of peas.

22. In Mendel’s experiments, only one of the two contrasting forms of a character was expressed in the F1 generation. • The other form reappeared in the F2 generation in a 3:1 ratio

23. Factors are Genes on chromosomes • Forms are called : alleles

24. Rule of Dominance • By definition, • the trait that shows up in the F1 generation is dominant • the trait that disappears is recessive

25. What do these mean? • P • F1 • F2

26. Out of Mendel's work came two "Laws" of inheritance: • 1) Mendel proposed that heredity was controlled by paired factors that segregated when gametes formed and rejoined at fertilization and, • 2) The principle of independent assortment indicates that the segregation of one pair of factors, or Alleles, has no influence over the way any other pair segregates.

27. Gregor Mendel approached problem-solving in new and different ways.

28. 1. He worked with pure strains of garden peas. • The flowers have both male (stamen- anther and filaments) and female (pistil- stigma, style and ovary) reproductive parts.

29. He removed (emasculated) the male part (anthers and filaments that produce the male sex cells) so he could control the way each plant was fertilized. • This was done artificially by mechanically transferring the male sex cells from the desired plant to the stamen of the emasculated plant. • The offspring using this procedure are referred to as "crosses".

31. 2. He only worked with traits of the peas that could easily be seen. • He experimented using only one trait at a time. • Traits included a) stem length, b) flower color or c) seed shape.

32. 3. Mendel kept detailed records of his "crosses". • He counted the pea offspring and calculated, using mathematics, how often the trait occurred in the offspring.

33. Mendel believed that traits were determined by individual units called factors. • He believed that each offspring received a factor from each parent. • Today these factors are called genes.

34. Punnett Squares • The square shows how the alleles separate when gametes are formed. • It shows the possible combinations of the alleles when fertilization occurs.

35. Punnett Square • G= green peas g= yellow peas pure breed green Pure breed yellow

36. What are the results? • 100% are phenotype green • 100% are genotype heterozygous 4/4

37. Both parents are: heterozygous genotype and brown hair phenotype

38. What are the results? = Brown hair = blonde hair

39. Chances for Genotypes 1/4 1/4 2/4

40. Chances for Phenotypes ¾ Brown ¼ blonde

41. Flower color • R = red • r = white

42. Mendel's First Law: Law of Segregation • Mendel guessed that the TWO genes for flower color separate or segregate, when the sex cells form during meiosis. • In the case of the hybrid pea flowers (RR), each plant would have one gene (allele) for red color (R) and one gene (allele) for white color (r). • These two genes would separate or segregate from each other during the formation of the sex cells. About half of the sex cells would receive the gene for red color and the other half the gene for white color.

43. Meiosis/ sex cell formation Sperm cells each get one allele

44. Mendel's Law of Segregation states- • The two genes that determine a particular trait will separate when sex cells form. • Half of the cells will receive one gene (allele) and half of the cells will receive the other gene (allele) of the allelic pair.

45. _ The law of segregation states that the two alleles for a gene separate when gametes are formed.

46. Mendel's Second Law • - the law of independent assortment; • Random distribution of alleles occurs during gamete formation. Genes on separate chromosomes sort independently during meiosis. • during gamete formation the segregation of the alleles of one allelic pair is independent of the segregation of the alleles of another allelic pair

47. The law of independent assortment states that two or more pairs of alleles separate independently of one another during gamete formation.

48. In other words… • Where the allele for color goes is not connected to where the gene for height goes. Color R Color r Height T Height t

49. R r r R T T t t t

50. Mendel’s Theory • _ Different versions of a gene are called alleles. An individual usually has two alleles for a gene, each inherited from a different parent.