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Mendelian Genetics

Mendelian Genetics. How is genetic information passed?. Thought 1- The Homunculus- tiny, complete person inside a sperm that grows into a full grown person Thought 2- Blended Heredity-. Then comes Mendel…. Gregor Mendel- 1860’s - Austrian monk

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Mendelian Genetics

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  1. Mendelian Genetics

  2. How is genetic information passed? • Thought 1- The Homunculus- tiny, complete person inside a sperm that grows into a full grown person • Thought 2- Blended Heredity-

  3. Then comes Mendel….. • Gregor Mendel- 1860’s - Austrian monk • Worked with Pisum sativum (pea plants)- interested in statistics of inheritance • Never knew of genes or DNA • Just lucky!!

  4. Why peas? • Small • Easy to grow • many offspring • mature quickly • 7 identifiable traits • can be self- and cross-fertilized

  5. What is a trait? • TRAIT: the physical effects of the expression of a gene • the hair is blonde • the bunny has spots • The cat has white feet

  6. 1.)Flower color 2.)Seed Color 3.) Seed shape 4.) Pod Color 5.) Pod shape 6.) Flower position 7.)Plant height Each trait shows as 1 thing or another i.e.- flowers either purple or white pods either inflated or wrinkled Traits Mendel Chose to observe

  7. Mendel’s Experiment • 3 Steps • Step 1- Create purebred parental generation • Allows self-fertilization for many generations to get purebred white and purebred purple flowering plants • PUREBRED: organism which has the same traits as both parents • Yorkshire Terriers, Dalmatians, etc.

  8. PARENTAL (P) Generation

  9. STEP 2 • Creates the F1 generation- First filial- latin for son or daughter • Crosses Purple plant x White Plant • Results- • All had purple flowers!!!!!

  10. STEP 3 • F2 Generation • Crosses 2 F1 plants F1 x F1 (purple x purple) • Results--- • 3:1 ratio of purple to white!

  11. What’s an allele? • ALLELE: a version of the expression of a gene • all genes have 2 alleles for their expression • a brown eyed person may have 2 “brown” alleles or 1 “brown” and one “blue” allele

  12. Mendel Summarizes Data • 1) parents must transmit a “factor” containing information- we know these as genes now • 2) Different forms of “factors”= ALLELES • Genetic makeup of all alleles= genotype • Physical appearance due to alleles= phenotype • 3)Dominant alleles mask recessive alleles • 4) Everyone has two factors-1 from each parent- if they are the same= homozygous, if they are different= heterozygous

  13. DOMINANT: gene that is fully expressed when two alleles are paired RECESSIVE: gene that is not expressed when paired with a dominant gene or that produces a different version of the trait than the dominant

  14. Which one is dominant? Brown eyes or blue? • a person with 2 “brown” alleles has brown eyes • a person with 1 “brown” and 1 “blue” has brown eyes • or a person with 2 “blue” alleles has blue eyes

  15. LAW OF DOMINANCE - the dominant allele is expressed and the recessive allele is hidden, if a dominant allele is not present, the recessive will be expressed

  16. MENDELS LAWS/modernized LAW OF SEGREGATION- during meiosis, gene pairs separate and end up in individual gametes LAW OF INDEPENDENT ASSORTMENT - during meiosis, traits will sort independently of each other

  17. Revisiting Law of Segregation

  18. Revisiting Law of Independent Assortment

  19. Chromosome Theory of Heredity the material of inheritance is carried by genes on chromosomes, and the genes occur in pairs on homologous chromosomes the gene pairs can be found in different types called alleles and are found at the same place on each chromosome, called the LOCUS

  20. BASIC GENETIC SHORTHAND in working with genes, scientists have found that assigning alphabetical letters to each trait makes the traits easy to follow through generations

  21. Rules: Dominant alleles are written as CAPITAL letters Recessive alleles are written as lower case letters Traits are expressed in pairs, so the diploid condition will always have 2 of the same letters representing the trait examples include BB, Bb, bb

  22. REVIEW GENOTYPE- the types of genes an organism has, expressed in letters PHENOTYPE - the physical expression(appearance) of the gene pair

  23. HOMOZYGOUS- a genotype description of a gene pair with both dominant or both recessive alleles HETEROZYGOUS - a genotype description of a gene pair with 1 dominant and 1 recessive allele in the gene pair

  24. Example of Genetic Law In peas, yellow pea color is dominant over green pea color. Just because it is more commonly seen, does not mean that trait will be the dominant trait

  25. Phenotype Genotype Genotypic Expression Yellow Pea BB Homozygous dominant Yellow Pea Bb Heterozygous Green Pea bb Homozygous recessive

  26. Ideas to Keep In Mind… it is simpler to discuss one gene pair at a time an organism will have many traits expressed at the same time not all genes are expressed by 2 alleles, some may be expressed by multiple alleles, like blood type not all traits are expressed by just one gene, some may involve many genes like skin color-determined by the expression of 21 different gene pairs

  27. MAKING PREDICTIONSUSING GENES To improve crops To help produce an improved product people will buy To predict possibility of genetic disorders Paternity Tests

  28. HOW TO PREDICT use of PUNNETT SQUARES MONOHYBRID CROSSES one trait being crossed use 4 squares DIHYBRID CROSSES two traits being crossed use 16 squares

  29. In the Hairy Apeloideus, blue ears are dominant to red ears. If a heterozygous individual is crossed with an red eared individual, what is the probability that the offspring will have red ears?

  30. DIHYBRID CROSSES • 2 Factors • Example- • In Humans curly hair (C ) is dominant to straight hair (c) and freckles (F) are dominant to not having freckles (f). If a man who is heterozygous for curly hair and doesn’t have freckles marries a woman who has straight hair & is homozygous dominant for freckles, and they have babies, what could the possible phenotypes in their offspring be??

  31. Completing the Cross • 1- Figure out gametes- use the FOIL method- SEE BOARD • 2- Write gametes above and on side of boxes- use 16 squares this time • 3- Letter pairs go back together in offspring

  32. Completing the Cross • 1. Determine the letter you’ll use • 2. Determine the gametes of the parents • 3.Make your punnett square

  33. DIFFICULT PREDICTIONS Mendel was lucky because his “factors” behaved in a predictable fashion and there were only 2 phenotypes per trait Not all traits are so orderly

  34. Incomplete Dominance the genes in the pair are not necessarily dominant or recessive, but become “BLENDED” in the offspring heterozygotes show the blending, homozygotes show one of 2 expressions

  35. Examples in Humans • Familial Hypercholesterimia- caused by defective proteins that cannot remove LDL from blood- leads to atherosclerosis- • Sickle Cell Anemia

  36. CODOMINANCE both genes become expressed, but are individually recognizable may involve multiple alleles

  37. ROAN Animal Coats • Red haired parent + White haired parent = red and white haired offspring (Roan- horses and cattle)

  38. Examples in humans • Tay-Sachs disease- in children- fat buildup on brain • Gene is recessive but heterozygotes have good and bad enzymes present- but they’re normal • Blood Types A, B, AB, O- different antibodies present on RBCs

  39. Other Influences Polygenic traits have more than one gene pair controlling expression Pleiotropyoccurs when a single gene affects more than one trait Multiple Alleles have more than 2 phenotypes expressed

  40. Blood Type Genetics • Blood is … • 1. Plasma • 2. Cells • a. Platelets • b. white blood cells • c. Red blood cells

  41. Blood Type genetics • Genes involved • I = dominant • i = recessive • Rather than just 2 alleles, there are many

  42. Blood Types A B AB O Genotypes IAIA or IAi IBIB or IBi IAIB ii Blood Type Genetics

  43. http://anthro.palomar.edu/blood/table_of_ABO_and_Rh_blood_type_frequencies_in_US.htmhttp://anthro.palomar.edu/blood/table_of_ABO_and_Rh_blood_type_frequencies_in_US.htm

  44. Blood Type Genetics • Red Blood cells contain surface antibodies(like little flags)- marker proteins • A blood contains A proteins and anti- B antibodies • B blood contains B proteins and anti- A antibodies • O blood contains no proteins and anti- A and anti- B antibodies • AB contains A and B proteins but no antibodies • http://learn.genetics.utah.edu/units/basics/blood/types.cfm

  45. Blood Type genetics • Antibodies recognize foreign blood and cause agglutination (clumping) • Transfusions- example- person with Type A blood must be matched with A or O ; otherwise Anti B antibodies will recognize B blood and reject it • Type 0 = universal donor • Type AB = universal receiver

  46. PROBLEM • If a man with O blood type marries a woman with type AB blood, what blood types are possible in their children?

  47. THE PAURY MOVICH SHOW TODAY’S SHOW: “I AM NOT THE FATHER!”

  48. THE PAURY MOVICH SHOW Next Week’s Show- My Dad is an Alien!

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