Howe Great Union Rags

3. Howe Great Union Rags • http://www.pedigreequery.com/howe+great • http://www.pedigreequery.com/union+rags

4. The Sphynx cat, is a rare breed. It is sometimes known as the Canadian Hairless, originating in Ontario, Canada in 1966, when a black and white house cat gave birth to a male hairless kitten, similar to the Mexican Hairless. Nature periodically produces naturally hairless cats.

5. In 1930, Dr Clyde Keller developed Himalayan Cat breed by crossing between Siamese and Persian

7. Chapter 8Mendel and Heredity Quick Review p. 161

8. DNA from the beginning • http://www.dnaftb.org/

9. Origins of Genetics • Heredity – the passing of characters from parents to offspring – was one of the greatest mysteries of science • Gregor Johann Mendel, Austrian monk, who carried out experiments on garden pea – first to develop rules that accurately predict patterns of heredity

10. Genetics - the branch of biology that focuses on heredity • Mendel repeated experiments of a British farmer, T.A. Knight • Cross – refers to the mating or breeding two individuals • Knight used garden peas • Mendel counted the number of each kind of offspring & analyzed the data

11. Useful Features in Peas • Several characters of the garden pea (Pisum sativum) exist in two clearly different forms • Character – used to mean inherited characteristics, flower color • Trait – to a single form of a character, purple flower

12. Male & female reproductive parts of garden peas are enclosed within the same flower – helping control mating • Self-fertilization – fertilize itself • Cross fertilization- transfer the pollen from flower to another

13. Stamens – male reproductive organs that produce pollen • Pistil – female reproductive part that produces eggs

14. Garden pea is small, grows easily, matures quickly, and produces many offspring • Results can be obtained quickly, and there are plenty of subjects to count

15. Traits Expressed as Simple Ratios • Mendel initial experiments were monohybrid crosses • Monohybrid cross – a cross that involves one pair of contrasting traits • His experiments had 3 steps: • Step 1: allowed each variety to self-pollinate for several generations • True-breeding – all the offspring would display only one form of the character

16. P generation (parental generation) – the first two individuals that are crossed in a breeding experiment • Step 2 - Mendel cross-pollinated two P generation plants that had contrasting traits • Offspring were called filial generation or F1 generation • Examined and recorded the number of F1 plants expressing each trait

17. Step 3 – Mendel allowed the F1 to self-pollinate • Called the offspring of the F1 generation the second filial generation or F2 generation • Each F2 generation was characterized and counted

18. Mendel’s Results • The F1 generation showed only one form of the trait • When F1 generation was allowed to self-pollinate, the missing trait reappeared in some of the plants • A ratio is a comparison of two numbers and can be written as a fraction (705/224) or with a colon 705:224

19. Homework • Write the questions with the answers • P. 165 section 1 review 1-6 • P. 184 1,6,7

20. Section 2 Mendel’s Theory A Theory of Heredity

21. Before Mendel, many people thought offspring were a blend of the traits of their parents • Mendel correctly concluded that each pea has two separate “heritable factors” • Gametes fuse during fertilization, the offspring has two factors for each character, one from each parent

22. Mendel’s Hypotheses • Four Hypotheses Mendel developed – foundation of genetics • 1) For each inherited character, an individual has two copies of the gene – one from each parent • 2) There are alternative versions of genes – now called alleles – different versions of a gene

23. 3) When two different alleles occur together, one of them may be completely expressed, while the other may have no observable effect on the organism’ appearance • Dominant – the expressed form of the character – • Recessive – the trait that was not expressed when the dominant form was present –

24. 4) When gametes are formed, the alleles for each gene in an individual separate independently of one another. Thus, gametes carry only one allele for each inherited character. When gametes unite during fertilization, each gamete contributes one allele. • Because of the way gametes are produced during meiosis

25. Mendel’s Findings in Modern Terms • Letters are often used to represent alleles • Dominant alleles are indicated by writing the first letter of the character as capital letter • Recessive alleles are also indicated by writing the first letter of the dominant trait, but the letter is lowercase

26. Homozygous- two alleles of a particular gene present in an individual are the same – recessive trait is always homozygous, but a dominant may not be ex. TT - tall • Heterozygous – the alleles of a particular gene present in an individual are different Tt - tall

27. Since only the dominant allele is expressed, you can not tell if an organism is homozygous or heterozygous • Genotype – the set of alleles that an individual has for a character • Phenotype – the physical appearance of a character; determined by which alleles (genotype) are present

28. The Laws of Heredity • Law of Segregation – the two alleles for a character segregate (separate) when gametes are formed

29. Law of Independent Assortment • Mendel conducted dihybrid crosses to study how different pairs of genes are inherited • Dihybrid cross – a cross that considers two pairs of contrasting characters • Mendel found that for the characters he studied, the inheritance of one character did not influence the inheritance of any other character

30. Law of Independent assortment – that the alleles of different genes separate independently of one another during gamete formation • This law applies only to genes that are located on different chromosomes or are far apart on the same chromosome

31. Mendel called the traits “factors” • Today we call them genes – units of heredity are portions of DNA, which are found on the chromosomes that are inherited from its parents

32. Homework • Section 2 Review p. 169 restate or rewrite the questions 1-4,6 • Chapter Review p. 184 & 185 5,8,9, 13, 16

33. Section 3Studying Heredity Punnett Squares

34. Breeders must be able to predict how often a trait will appear • “ Expected” results of genotypes or phenotypes in a cross is to use a Punnett square • Punnett square- a diagram that predicts the outcome of genetic cross by considering all possible combinations of gametes in the cross • Named for Reginald Punnett

35. The possible gametes that one parent can produce are written along the top of the square • The possible gametes that the other parent can produce are written along the left side of the square • Each box inside the square is filled in with two letters by combining the allele from the top and side • The letters in the boxes indicate the possible genotypes of the offspring

36. One pair of Contrasting Traits • Monohybrid cross – a cross that considers one pair of contrasting traits between two individuals • Punnett square can be used to predict outcome between a homozygous purple flower with a homozygous white flower (P generation) • All F1 generation is purple and heterozygous

37. Punnett square can also predict the results of a cross of two heterozygous F1 generations • Genotype: ¼ homozygous (RR); ½ heterozygous (Rr); ¼ homozygous (rr) • Ratio would be 1:2:1 • Phenotype: ¾ purple; ¼ white Ratio would be: 3:1 Punnett square allow direct and simple predictions about outcomes

38. Synpolydactyly HOH gene defect semidominant

39. Determining Unknown Genotypes • Breeders need to know if a breeding organism is homozygous or heterozygous • Test Cross – crossing an individual whose phenotype is dominant, but whose genotype is not known, with a homozygous recessive individual • B = black • b = white

40. If all the offspring are purple, then the genotype of the unknown individual is PP and all the offspring will be Pp • If ½ of the offspring are purple and ½ are white then the genotype of unknown individual is Pp and ½ of the offspring will be Pp and ½ will be pp

41. Outcomes of Crosses • Probability – the likelihood that a specific event will occur • Can be expressed in words, as decimals, as percentages, or as fractions; we’ll use fractions or ratios • Probability = Number of one kind of possible outcome total number of all possible outcomes

42. Racing Game with One Die • http://www.shodor.org/interactivate/activities/RacingGameWithOneDie/

43. To find the probability of two independent events that occur in sequence, find the probability of each event occurring separately, and then multiply the probabilities. This multiplication rule is defined symbolically below. Note that multiplication is represented by AND. • Multiplication Rule 1:   • When two events, A and B, are independent, the probability of both occurring is: • P(A and B) = P(A) · P(B)  

44. Probability of a specific Allele in a Gamete • Same formula can be used to predict the probability of an allele being present in a gamete • If the alleles are the homozygous, then the probability would be ___ • If the alleles are heterozygous, then the probability would be ___

45. Probability of the Outcome of a Cross • Both parents must be considered when calculating the probability of the outcome of a genetic cross • Tossing two coins at the same time • To find the probability that a combination of two independent events will occur multiply the separate probabilities of the two events • ½ x ½ = ¼

46. Inheritance of Traits • Pedigree – a family history that shows how a trait is inherited over several generations • Helpful if a trait causes a genetic disorder

47. Carriers are individuals who are heterozygous for an inherited disorder, but do not show symptoms of the disorder • Carriers can pass the allele for the disorder to their offspring

48. Autosomal or Sex-linked • If a gene is autosomal, it will appear in both sexes equally • If a trait is sex-linked, its effects are usually seen only in males • Sex-linked gene’s allele is located only on the X or Y chromosome • Most sex-linked genes are carried on the X chromosome and are recessive

49. Sex-linked traits • Red-green color blindness • Fragile X syndrome • Hemophilia • Duchenne muscular dystrophy Boys inherit from mother

50. Dominant or Recessive?Heterozygous or Homozygous? • Autosomal dominant, every individual with the condition will have a parent with that condition • Homozygous or heterozygous dominant, the trait will show up • Noonan Syndrome – genetic disorder that prevents normal development of various parts of the body