2. Heredity  The passing of traits from parents to their offspring Causes children to resemble their parents.  Genetics - The study of heredity

3. Gregor Mendel - the father of modern genetics  Austrian monk - trained in mathematics and natural sciences.  Work conducted over period of 8 years with common garden peas -1856 to 1865. Kept careful records. Applied mathematical studies to his work. Worked with different kinds of plants. Selected peas

5. Selected peas because they:  Grew rapidly.  Produced many seed (offspring).  Flower structure made it easy to control Pollination Transfer of pollen from stamen to pistil of a flower. Pistil - female reproductive structure - egg at base. Stamen - male reproductive structure - produces pollen contains sperm. Self –pollination - process where pollen from stamen falls on pistil of the same flower. Cross-pollination - process where pollen from stamen of 1 flower falls on pistil of another flower on another plant.

7. Identified 7 different characteristics in pea plants Each had two contrasting forms.  Seed Shape - Round Vs. Wrinkled  Seed Color - Yellow Vs. Green  Flower Color - Purple Vs. White  Pod Shape - Inflated Vs. Constricted  Pod Color - Green Vs. Yellow  Flower Position - Axial Vs. Terminal  Plant Height - Tall Vs. Short

9. His experiments were different from earlier workers  Studied only 1 trait at a time, rather than everything about the offspring at once.  Studied results of many matings and pooled the results - earlier workers had looked at only a few offspring from a single mating Counted 7324 peas for seed shape (F2 generation) Counted 8023 peas for seed color (F2 generation)  Used the large number of offspring to discover definite ratios of characteristics among the offspring. 5474 Round Seed: 1850 Wrinkled Seed 2.96:1 6022 Yellow Seed: 2001 Green Seed 3.01:1

10. Mendel's Experiments and Observations  When the plants were allowed to self-pollinate, the trait always stayed the same - called them "Truebreeding " or "Pure "plants; Tall plants x Tall plants produced Tall plants.  Removed stamens from the pure plants that produced wrinkled seeds. Dusted pistil with pollen from plants that produced only round seeds Called these the Parental or P1 generation  All of the offspring of this cross resulted in plants that had round seed Called this the First Filial or F1 generation; Also called Hybrids Hybrid - offspring from a cross between parents differing in 1 or more traits. Found that 1 trait of the parents always disappeared in the F1 generation.  The F1 generation plants were allowed to self-pollinate Called the next generation the Second Filial or F2 generation. Found that some F2 plants had round seed; some had wrinkled seeds. Similar results were obtained with the other traits always 75% of 1 trait; 25% of other trait - a 3:1 ratio.

11. Mendel’s Cross P1Round Seed x Wrinkled Seed F1All Hybrid Round Seed Hybrid Round Seed x Hybrid Round Seed F2¾ Round Seed; ¼ Wrinkled Seed

12. Mendel's Conclusions  Did not know anything about cell reproduction Work based on hypothesis that Factors or units carried the traits he was studying - called Genes today.  Observed that offspring of true breeding plants with contrasting traits showed the trait of only 1 parent plant Called trait Dominant – disappearing trait called Recessive  Observation lead to his Law of Dominance - one form of a hereditary trait, the dominant trait, Dominates or prevents the expression of the recessive trait.  Mendel hypothesized that factors exist in pairs since the plants which had 1 trait could produce seeds with the opposite trait.

13. Mendel’s Conclusions  Mendel hypothesized that paired factors separate or segregate during gamete formation - lead to Law of Segregation - During gamete formation the pairs of genes responsible for each trait separate so that each gamete contains only 1 gene for each trait.  During fertilization the zygote gets 1 gene for the trait from mom and 1 from dad.  The different forms of a gene for a trait are known as Alleles  Combination of alleles or genetic makeup is the organism’s Genotype  The appearance of the organism regardless of its genetic makeup is its - physical appearance - Round, yellow, etc.

15.  Dominance is expressed by a capital letter - usually the first letter of the dominant trait; Recessive trait is expressed by a small letter (same as the dominant trait) For round Vs. wrinkled seed - R - dominant; r - recessive Hybrid would be Rr  During gamete formation the pairs of genes responsible for each trait separate so that each gamete contains only 1 gene for each trait. Rr / \ R r

16. Mendel’s Cross P1Round Seed x Wrinkled Seed RRxrr F1All Hybrid Round Seed (Rr) Hybrid Round Seed x Hybrid Round Seed Rr xRr F2¾ Round Seed; ¼ Wrinkled Seed RR, Rr rr

18. Genetic Terminology  Dominant - trait which stays visible  Recessive - trait which disappeared  Alleles - alternate forms of a gene for a trait  Genotype - genetic makeup of a trait  Phenotype - physical appearance of a trait  Homozygous - both alleles are the same  Heterozygous - two alleles are different  Homozygous Dominant - pure dominant  Homozygous Recessive - pure recessive  Heterozygous Dominant - Hybrid with 1 dominant -

19. Mendel’s Laws  LAW OF DOMINANCE - one form of a hereditary trait, the dominant trait, dominates or prevents the expression of the recessive trait.  LAW OF SEGREGATION - During gamete formation the pairs of genes responsible for each trait separate so that each gamete contains only 1 gene for each trait.  LAW OF INDEPENDENT ASSORTMENT - Alleles segregate independently of each other during gamete formation.

20. The likelihood of an event occurring as expressed as a ratio or a percentage.  Flipping a coin – ½ heads; ½ tails  Cards - Chance of drawing an ace –4/52 or 1/13 Chance of drawing a spade - 13/52 or 1/4 Chance of drawing the Ace of Spades 1/13 x 1/4 = 1/52

21. Product Rule  To find the probability of 2 events occurring you multiply the individual probabilities. Chance of a head – ½ ; Chance of another head – ½ Chance of 2 heads in a row – ½ x ½ = ¼ Chance of 4 heads in a row – ½ x ½ x ½ x ½ = 1/16  Each gamete has ½ chance of getting a particular allele Homozygous Dominant - RR: Alleles - R or R = 1/1 Homozygous Recessive - rr: Alleles - r or r = 1/1 Heterozygous Dominant - Rr: Alleles - R or r; ½ R; ½ r

22. PUNNETT SQUARE  Special chart used to show possible combinations resulting from a cross of 2 organisms.  Put female gametes along top; male gametes along left side  Squares show possible genotypes of offspring -used to determine phenotype and ratio of offspring.  Used to predict; it doesn’t mean it will happen

23. MONOHYBRID CROSS - involves only one set of contrasting factors for a trait  Cross a homozygous yellow with a homozygous green Yellow – dominant (Y); green - recessive (y) Y Y P1 YY x yy y F1 all Yy heterozygous yellow y  Cross two of the F1 generation Y y Yy x Yy Y F2 – ¼ YY; ½ Yy; ¼ yy ¾ Yellow; ¼ green y Yy YYYy yy

24. DIHYBRID CROSS - involves two sets of contrasting traits at one time; genes are on separate chromosomes  Each gamete contains 1 allele for each trait  LAW OF INDEPENDENT ASSORTMENT - Alleles segregate independently of each other during gamete formation.

25. Het Round, Het Yellow RrYy x Het Round, Het Yellow RrYy Gametes: RY Ry rY ry

26. INCOMPLETE DOMINANCE/NONDOMINANCE  Phenotype between dominant and recessive trait  Heterozygous condition  Example - Four-O-Clocks RR - red flowers rr - white flowers Rr - Pink flowers  Cross of 2 pink flower plants - Rr x Rr Results – ¼ red (RR); 2/4 (½) Pink (Rr); ¼ white

28. Determination of Sex  By the Sex Chromosomes - x or y Other chromosomes are called Autosomes  Male - xy; Female - xx  Get ½ males and ½ females on Punnett square x x x y xy

30. SEX LINKED CHARACTERISTICS  Recessive trait linked with a certain sex - usually males  Carried on the x-chromosome; Male has only 1 x, the trait is visible Females with 2 x's - not visible if 1 of the x has a dominant gene for the trait.  Female only shows trait in homozygous recessive.  Woman is called a "Carrier" in heterozygous condition.  Examples: Red-Green color blindness Hemophilia

31. MaleFemale

33. MULTIPLE ALLELES  More than 2 alleles exist for a particular trait  In humans - blood types is an example of multiple alleles 3 different alleles - A, B, O Alleles A and B are codominant O is recessive

34. Blood Type  Due to presence of antigens on the red blood cells - produces antibodies in blood Type A - Antigen A on cells Plasma contains anti B Type B - Antigen B on cells Plasma contains anti A Type O - No Antigens on cells Plasma has anti A and anti B Type AB - Antigens A and B on cells Plasma lacks anti A and anti B

36. Phenotypes and genotype combinations  Type A - AA or AO  Type B - BB or BO  Type AB - AB  Type O - OO

37. Blood Donor Receives Group to from O O, A, B, AB O Universal Donor A A, AB O, A B B, AB O, B AB AB O, A, B, ABUniversal Recipient

38. GENE LINKAGE  Concerned with the presence of 2 different genes on the same chromosome  Does not follow usual dihybrid results - follows monohybrid.  Variation can occur due to crossing over - pieces of chromatids exchange places during synapsis of tetrads in meiosis.

39. LETHAL GENES  Genes which can cause death or harm in the homozygous condition.  Examples: Sickle-cell anemia PKU Tay Sachs - Jews of middle eastern European origin. Diabetes mellitus

41. NONDISJUNCTION  Failure of chromosomes to segregate properly during gamete formation.  Can involve sex chromosomes as well as the autosomes - zygote gets an improper number of chromosomes  Examples: Down's Syndrome - three #21 chromosomes - autosomal Turner's Syndrome - has only 1 x, no y chromosome - female Klinefelter's Syndrome - xxy - male Jacob’s Syndrome- xyy - male –thought to show criminal behavior at one time; not any higher.

42. Normal Male Male – Down’s

43. Klinefelter’s Syndrome Turner’s Syndrome Jacob’s Syndrome

44. MUTATIONS  Change in the genetic code or genes of an organism.  Can occur naturally or by exposure to agents that produce mutations. Breaks during crossing over which do not reattach. Increased chance of breakage by exposures to mutagens Mutagens - agents that cause mutations. Radiation - x-rays, UV, gamma Chemicals