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Heredity and Mendel Meiosis

Heredity and Mendel Meiosis. Chapter 11. Vocabulary and Questions. Trait Genetics Cross Law of segregation Gene Allele Homozygous Heterozygous Dominant Recessive Genotype Phenotype P.98 1-5 P.100 1-4. Gregor Mendel.

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Heredity and Mendel Meiosis

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  1. Heredity and MendelMeiosis Chapter 11

  2. Vocabulary and Questions • Trait Genetics Cross • Law of segregation Gene • Allele Homozygous Heterozygous • Dominant Recessive Genotype • Phenotype • P.98 1-5 • P.100 1-4

  3. Gregor Mendel • Gregor Mendel - Austrian monk (Austrian not Australian-spoke German) who used peas in his discovery of the laws of heredity • Father of Genetics

  4. Studied traits • Flower color • Flower position • Seed color • Seed shape • Pod shape • Pod color • Stem length

  5. Genetics • Genetics - branch of biology devoted to the study of heredity

  6. Genetics • Heredity – passing on of characteristics from parent to offspring Characteristics: From Fatal Diseases to just Looks

  7. Genetics • Trait – inherited characteristics (example: hair color or height or temperament)

  8. Genetics • Alleles – different gene forms (example: the hair trait includes dark hair and light hair alleles)

  9. Mendel’s traits Alleles Domminant Allele Recessive Allele • Flower color • Flower position • Seed color • Seed shape • Pod shape • Pod color • Stem length

  10. Alleles

  11. Genetics • Gametes - sex cells: egg, sperm & pollen…

  12. Genetics • Fertilization – uniting of male and female gametes

  13. Genetics • Pollination – transfer of pollen to female organ of flowers

  14. Genetics • Law of Segregation – alleles must separate when gametes are formed • Law of Independent Assortment - each trait can be passed on in different combinations

  15. Genetics • Homozygous –a pure bred organism that has the same alleles AA, aa, BB, … • Heterozygous – a hybrid organism that has different alleles Aa, Bb, …

  16. Genetics • Dominant trait– observed trait or the stronger trait • Recessive trait – weaker trait Lancaster Co., Pennsylvania: By chance, at least one of the original 30 Amish settlers in this community carried a recessive allele that results in short arms and legs and extra fingers and toes in offspring. Because of the small gene pool, many individuals inherited the recessive allele over time. Today the frequency of this allele among the Amish is high: 1 in 14 rather than 1 in 1000 in the larger population of the U.S.

  17. Genetics • Phenotype – what the organism “looks” like (example: color, shape, speed, smell, height, personality…) • Genotype – gene or allele combination (example AA, Aa, aa, Aabb…)

  18. Genetics • Horse hair color GENOTYPE/PHENOTYPE

  19. Vocabulary and Questions • Punnett Square Monohybrid cross • Dihybrid cross Probability • Carrier Sex-linked genes • Incomplete dominance • Codominance Polygenic traits • Pedigree Karyotype • P.104 1-4 P. 121 1,2,4,5,7 • P.114 1-4

  20. Punnett Square • Punnett Square – short hand way to predict possible genotypes of offspring • Monohybrid cross – takes one trait into consideration when doing a punnett square

  21. Punnett Square What is the bird’s phenotype? What is the bird’s genotype? Set up and work a punnett square for two of these birds Its genotype is Aa.

  22. Punnett Squares • Dihybrid cross – takes two traits into consideration when doing a punnett square A is orange feathers. a is blue feathers. B is orange bill. b is blue bill These birds have four genes one for orange feathers and one for blue feathers; one for orange bill and one for blue bill.

  23. Eye color….. Dihybred Two completely heterozygous parents Bb/Gg x Bb/Gg

  24. Incomplete Dominance • A cross where one allele is not completely dominant over another, so a mixture of both are seen. Red + White = Pink

  25. Codominance • Phenotypes of both alleles are expressed. Red + White = Red and White (not pink)

  26. Polygenic • “Having many genes” • More than one gene is responsible for certain phenotypes. Ex: Skin color, hair color…

  27. Sex-Linked Traits • Traits that are passed on by only one chromosome (either X or Y). • X-linked is passed on by the X chromosome only. XaXa, XaY • Y-linked is passed on by the male only because it is passed on the Y chromosome. XYa • These traits still follow the dominance and recessive principles.

  28. Sex-Linked Traits • Most common: Recessive, X-Linked • Why? X chromosomes are bigger than Y!!! • Females [XX] must have 2 copies of this trait to show it (one on each X chromosome) • Males [XY] only need 1 copy (they only have one X; trait always comes from mother)

  29. Examples of Sex-Linked Traits All Examples are Recessive & X-Linked: • Color-blindness • Hemophilia • Muscular Dystrophy • High Blood Pressure • Fragile-X Syndrome

  30. Pedigrees A chart of an individual’s ancestors, used to predict and analyze the passing on of a certain gene down the family line.

  31. Guide to Reading Pedigrees

  32. Now you practice… Is this trait dominant or recessive? Could this trait be sex-linked? What are the genotypes of each individual?

  33. Gene Linkage • Law of Independent Assortment states that genes segregate independently during meiosis. • However, chromosomes have several genes on them, so genes found on the same chromosome are inherited together, unless crossing over occurs. • This is “gene linkage” • Gene maps are used to show the relative locations of each known gene on a particular chromosome.

  34. Gene maps • The closer together genes are on a chromosome, the more likely they will be inherited together!

  35. GENETIC DISORDER CHROMOSOME MAPS CHROMOSOME 1-Alzheimer disease, type 4 -Gaucher disease  -Prostate cancer  -Glaucoma  -Rh blood type  -TSH, beta chain  -Amylase  -Histone proteins  CHROMOSOME 2-Antibody, light chain  -Myosin, light chain  -Glucagon  -Mismatch repair 2 (hereditarynonpolyposis colon cancer, type 1, HNPCC)  -Waardenberg syndrome 

  36. CHROMOSOME 3-Rhodopsin (retinitis pigmentosa, partial color blind)  -Mismatch repair 1  -Colon cancer, nonpolyposis, type 2  -Small cell lung carcinoma  -Von Hippel-Lindau syndrome  CHROMOSOME 4-Alcohol dehydrogenase  -Red hair color  -Achondroplasia (dwarfism)  -Ellis-van Creveld syndrome  -Huntington disease

  37. CHROMOSOME 5-Diastrophic dysplasia  -Steroid 5-alpha-reductase-1 -Achondroplasia (dwarfism) ic kidney disease  CHROMOSOME 6-MHC (Major Histocompatibility Complex)  -HCG, FHS, LH, TSH, alpha chain  -Beta tubulin  -Juvenile onset diabetes  -Spinocerebellar atrophy  CHROMOSOME 7-Collagen 1, alpha 2 (Osteogenesis imperfecta)  -Trypsin  -Blue cone pigment (partial color blind)  -Cystic fibrosis -Obesity 

  38. CHROMOSOME 8-Burkitt lymphoma  -Werner syndrome  CHROMOSOME 9-ABO blood group  -Ultraviolet repair (xeroderma pigmentosum & skin cancer prone)  -Malignant melanoma  -Tuberous sclerosis  CHROMOSOME 10-Hexokinase (hemolytic anemia)  -Gyrate atrophy of the choroid and retina  -Multiple endocrine neoplasia 

  39. CHROMOSOME 11-Hemoglobin, beta chain (sickle cell anemia, thalessemia)  -Insulin (mutation NOT usual cause for diabetes)  -Parathyroid hormone  -Catalase  -FHS, beta chain  -Tyrosinase (Albinism)  -PAX6, Aniridia  -Ataxia telangiectasia  -Harvey ras oncogene  -Long QT syndrome  CHROMOSOME 12Tirose phosphate isomerase  Keratin  Phenylketonuria (PKU) Zellweger syndrome 

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