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Mendel ’ s Laws of Heredity

Mendel ’ s Laws of Heredity. Why we look the way we look. Mendel used peas. They reproduce sexually They have two distinct, male and female , sex cells called gametes Their traits are easy to isolate. Mendel crossed them. Fertilization - the uniting of male and female gametes

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Mendel ’ s Laws of Heredity

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  1. Mendel’s Laws of Heredity Why we look the way we look...

  2. Mendel used peas... • They reproduce sexually • They have two distinct, male and female, sex cells called gametes • Their traits are easy to isolate

  3. Mendel crossed them • Fertilization - the uniting of male and female gametes • Cross - combining gametes from parents with different traits

  4. What Did Mendel Find? • He discovered different laws and rules that explain factors affecting heredity.

  5. 1. Rule of Dominance • The trait that is observed in the offspring is the dominant trait (uppercase) • The trait that is masked inthe offspring is the recessive trait (lowercase)

  6. 2. Law of Segregation • Genes appear in pairs on homologous chromosomes • are SEPARATEDwhen gametes are formed • and recombine during fertilization

  7. 3. Law of Independent Assortment • Genes for different traits are inherited independentlyof each other • because homologous chromosomes move randomly to gametes Explains why siblings look different

  8. Genetics Continued • Dihybrid crosses • Exceptions to Mendelian Genetics • Incomplete vs. Complete Dominance • Codominance • Sex-Linked Genetics • Blood Types (Multiple Alleles)

  9. Monohybrid Vs Dihybrid • Monohybrid Cross- crossing parents who differ in only one trait (AA with aa) • Dihybrid Cross- crossing parents who differ in two traits (AAEE with aaee)

  10. S= yellow • s= green • Y= round • y= wrinkled How many round yellow? How many round green? How many wrinkled yellow? How many wrinkled green?

  11. S= yellow • s= green • Y= round • y= wrinkled Show a dihybrid cross between two complete heterozygotes How many round yellow? How many round green? How many wrinkled yellow? How many wrinkled green?

  12. S= yellow • s= green • Y= round • y= wrinkled How many round yellow? How many round green? How many wrinkled yellow? How many wrinkled green?

  13. Dihybrid Cross - 2 traits

  14. What’s on our agenda? • Monday: Welcome back! • Brief Genetics Review • Learn Blood Types & Blood type punnetts • Tuesday: Learn Pedigrees • Wednesday: Receive Genetics Test Study Guide • Material= Mendel’s laws, Punnetts, Dihybrids, Ratios, Codomiance, Incomplete Dominance, Sex-linked Inheritance, Blood types, Pedigrees • Thurs: Take Genetics Unit Test • Friday: Receive FULL YEAR study guide in preparation for MCAS (June 1 & 2). Due 5/31 (D & E, due 5/27 F Block • Left to cover: Ecology, Evolution

  15. Non-Mendelian Genetics: Exceptions to Complete Dominance

  16. Incomplete Dominance - Blend Heterozygous genotype= blend of two phenotypes RR= Red RW= pink WW= white

  17. Codominance – Both show Both alleles of the trait show in the heterozygote

  18. Codominance: Both traits show in heterozygotes Try these: what are the phenotype ratios? TRY ANOTHER!Calico Cat Colors B: Black Y: Yellow NOTES: Horse Fur Color R= Brown W= White

  19. Sex-Linked

  20. Sex-Linked

  21. Sex-linked Punnett • C= color-blindness • XX= Female • XY= Male • Is mom colorblind? • Is dad colorblind? • What is the chance that they have: • a colorblind girl? • a female carrier? • an unaffected male? • an affected male?

  22. Polygenic: controlled by many genes • Polygenic inheritance is a fancy term for those genetic traits that are controlled by more than 1 gene • Height, Skin Color • Because there are MANY genes that influence polygenic inheritance, you see a spectrum of phenotypes

  23. Blood Types: Multiple Alleles • What is multiple allele inheritance? • Non-Mendelian Inheritance Pattern • involves more than just 2 alleles • that means there is more than two phenotypes

  24. Blood Types: Multiple Alleles • Example: Blood Type (Red Blood Cells) • There are markers on the surface of RBCs • Our immune system has antibodies: ATTACK foreign invaders (germs, viruses) • YOU DO NOT WANT ANTIBODY for your BLOOD TYPE • What would be the result? Your immune system attacks your body!!

  25. Multiple Alleles - Blood Type Universal Donor (can give to everyone): 0 Blood…. why? Universal Recipient (can accept from anyone): AB Blood…..why?

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