1. Chapters 9 & 12: Genetics

2. Heredity – The passing of traits from parents to offspring Genetics – The study of heredity

3. Gregor Mendel Austrian monk Bred pea plants 1860 - developed laws of heredity

5. He cross-pollinated plants mms://204.13.204.36/Video9/mendelslaw.asf

6. He bred plants to be pure for certain traits Ex: Tall parent  tall offspring Short parent  short offspring Then he cross-bred plants with opposite traits Tall x short Round x wrinkled Yellow x green

7. Parents - P generation – tall x short Offspring – F 1 generation (1 st filial generation) All offspring were tall (short trait disappeared) Allowed F 1 generation to self-pollinate F 2 generation – 75% tall to 25% short (short trait reappeared) Repeated many times – always same ratios for each generation (see results slide #2)

9. Mendel’s Conclusions: There are 2 factors for every trait (today we know these factors to be genes – 1 from mother, 1 from father) One of these factors can be dominant over the other (the recessive trait) This is known as the Law of Dominance

10. The factors separate when the gametes (eggs & sperm) are formed –The Law of Segregation Each gamete only has 1 factor from each pair (haploid) Fertilization gives each new individual 2 factors again (diploid)

11. Mendel then crossed pure plants that differed in 2 traits Ex: yellow, round peas crossed with green, wrinkled peas F 1 generation always showed dominant traits F 2 generation had the following results: (see next slide)

12. F 2 :9 yellow, round 3 yellow, wrinkled 3 green, round 1 green, wrinkled

13. Based on these results, Mendel concluded that pairs of factors separate independently during meiosis – The Law of Independent Assortment Ex: Below, hairline and finger length are not dependent on each other

14. Alleles - various forms of a trait Ex: tall and short height curly and straight hair brown and blue eyes

15. Widow’s peak

16. The Epicanthal Fold (eye fold)

17. Genotype and Phenotype Genotype refers to the genes of an individual; can be represented by two letters Homozygous - both alleles are the same Homozygous dominant - WW Homozygous recessive - ww Heterozygous – alleles are different - Ww

18. Phenotype refers to the appearance of the individual. Both WW and Ww result in widow’s peak, the dominant trait ww will result in no widow’s peak, the recessive trait

19. Monohybrid Crosses Considers only one trait. Punnett square – chart used to determine probability Ratio shows # of offspring with dominant vs. recessive trait

20. Probability Determine the odds of an event occurring. Expressed as fraction or percentage Ex: (1/4) or 25% The probability that two or more independent events will occur together is the product of their chances occurring separately Ex: odds of having a boy = ½ Odds of having 2 boys = (1/2) x (1/2) = (1/4)

21. The chance of widow’s peak: WW or Ww = 75% or ¾ Chance of a continuous hairline: ww = 25% or 1/4 Odds of having 3 children with a continuous hairline: (1/4) x (1/4) x (1/4) = (1/64)

22. Dihybrid Cross Two traits are considered Genotypes of the parents require four letters (two for each trait).

23. Codominance - both alleles are equally expressed in a heterozygote Ex: Blood type – AB blood Incomplete dominance – heterozygous genotype shows an intermediate phenotype, representing a blending of traits. Ex: Curly, wavy, or straight hair in Caucasians

24. ABO Blood Types How your book shows blood type: Blood type (phenotype) Genotype AI A I A or I A i BI B I B or I B i ABIAIBIAIB Oii

25. Blood type (phenotype) Genotype AAA or AO BBB or BO AB OOO How your teacher shows blood type:

26. Inheritance of blood type

27. Incomplete dominance

28. Other examples of incomplete dominance: Plants called four o’clocks RR – red RR’ – pink R’R’ – white So a cross between two pink plants produces 1 red, 2 pink, and 1 white plant RRRR’ R’R’ RR’ R

29. Another example includes Sickle cell disease in humans Hb A represents normal hemoglobin; and Hb S represents the sickled condition –Hb A Hb A – normal –Hb S Hb S – sickle-cell disease –Hb A Hb S - have the intermediate condition called sickle-cell trait. Heterozygotes have an advantage in malaria- infested Africa because the pathogen for malaria cannot exist in their blood cells.

30. Sex determination: Female – XX Male – XY Always 50% chance of having a boy or a girl Male determines gender of baby XX XY XX X Y

31. Sex-Linked Traits Traits controlled by genes on the X or Y chromosomes X-linked or Y-linked Most X-linked traits are recessive, so a female would have to have two recessive genes to express the trait; a male would only need one. Y-linked traits are only passed from father to son

32. Examples of X-linked traits include Color blindness, Hemophilia, Muscular Dystrophy, Fragile X Syndrome PhenotypeGentoype Normal femaleXBXBXBXB Carrier femaleXBXbXBXb Affected female XbXbXbXb Normal maleXBYXBY Affected maleXbYXbY

33. Cross involving an X-linked allele

34. Pedigree Charts Constructed to show the pattern of inheritance of a characteristic within a family. The particular pattern indicates the manner in which a characteristic is inherited (suggests X-linked, dominant, etc.)

35. Normal female Carrier female Affected female Normal male Affected male Symbols used: Male can be a carrier for an autosomal trait.

36. Autosomal recessive pedigree chart

37. Autosomal dominant pedigree chart

38. Amniocentesis Uses a needle to extract amniotic fluid from the uterus of a pregnant woman from the 14 th to 17 th week of pregnancy. Up to 400 chromosome and biochemical problems can be detected by culturing fetal cells that are in the amniotic fluid. 0.3% chance of miscarriage with this procedure – do this test only if certain risk factors are present.

39. Amniocentesis

40. Chorionic Villi Sampling (CVS) Uses a thin suction tube to sample chorionic cells from the placenta as early as the fifth week of pregnancy. Chorionic cells are found in the placenta The cells do not have to be cultured, and karyotyping can be done immediately. 0.8% risk of miscarriage but can be performed earlier than amniocentesis.

41. Chorionic villi sampling