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Genetics

Genetics. Chapter 12. Genetics- study of patterns of inheritance and variations in organisms People have always wondered how traits are passed down. HISTORY OF GENETICS. Old Theory- “The Blending Theory” Parent’s traits are mixed and BLEND together in the offspring

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Genetics

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  1. Genetics Chapter 12

  2. Genetics- study of patterns of inheritance and variations in organisms • People have always wondered how traits are passed down

  3. HISTORY OF GENETICS • Old Theory- “The Blending Theory” • Parent’s traits are mixed and BLEND together in the offspring • EX: Red + Yellow Parent = Orange Offspring • *Can NEVER get back to the original colors*

  4. Blending Theory is NOT CORRECT!!!! • Gregory Mendel’s theory is…

  5. Gregor Mendel- monk who lived in Austria in the 1800s • Studied and did breeding experiments with garden pea plants

  6. Why did he use pea plants? • 3 reasons • Contrasting Traits (purple or white) • Self pollination (has female and male parts) • Easy to grow (matures quickly and requires little care)

  7. Mendel’s Theory • Parents will pass on genes to their offspring • What are genes? • Found in chromosomes • Holds the genetic information • Made up of DNA

  8. Mendel’s First Experiments • Allowed the pea plants to self pollinate for several generations. This created true breeding plants called the ‘P generation’ Ex: True self breeding purple pea plants will always make purple pea plants

  9. Mendel’s First Experiments 2. Mendel crossed a white “P generation” plant with a purple “p generation” plant. Called the offspring the ‘F1 generation’ and recorded the traits (colors) ***All of the f1 generation were purple***

  10. Mendel’s First Experiment • 3. Allowed the purple f1 generation to self pollinate and create the f2 generation Results: the white color returned! (3 purple flower for every 1 white flower) http://go.hrw.com/hrw.nd/gohrw_rls1/pKeywordResults?keyword=HX8GENF3

  11. Drawing of Mendel’s First Experiment

  12. Important terms to know • Allele- alternate form of a gene, leads to a unique trait • Ex: Eye color gene: blue allele and brown allele • Gene- specific DNA sequence found on a chromosome

  13. Important terms to know • Principleof dominance- some alleles are dominant and others are recessive • Dominant- the allele that is fully expressed • Recessive- the allele that is expressed when there is no dominant allele present

  14. Important terms to know • You need only one dominant allele for it to be expressed. • You need TWO recessive alleles to be expressed • Ex: blue eyes is recessive. You need 2 blue alleles to see blue.

  15. Important terms to know • Genotype- genetic make-up or combination of alleles • Represented by letters • Ex: BB, Bb, bb

  16. Important terms to know • Phenotype- the trait that results from the individual’s genotype • Expressed by a word • Ex: blue, curly, brown

  17. Important Terms to Know • When talking about alleles they can be described as homozygous or heterozygous • Homozygous- two identical alleles • Ex: 2 alleles for brown eyes or 2 alleles for blue eyes • Letters are the same: BB, bb, PP, pp

  18. Important Terms to Know • Heterozygous- two different forms of the same allele • Ex: 1 allele for brown eyes, 1 allele for blue eyes • Letters are upper and lower case: Pp, Bb, Tt

  19. Putting Genotype with Heterozygous or homozygous • Examples • Hh- Heterozygous dominant • HH- homozygous dominant • hh- homozygous recessive • BB, bb, Bb ?

  20. Punnett Squares • Punnett Square- graphic used to predict the results of a genetic cross. Shows the genotypes • EX (drawing):

  21. Monohybrid Cross • Crosses one genotype with another genotype

  22. http://learn.genetics.utah.edu/content/begin/tour/ • http://colorvisiontesting.com/ishihara.htm

  23. Punnet Square of the Pea plants • Genotypic ratio: • Phenotypic ratio:

  24. Punnett Square for Eye Color • Genotypic ratio: • Phenotypic ratio:

  25. Punnett Square for Hair Type • Genotypic ratio: • Phenotypic ratio:

  26. Punnett Square for ability to Bark • Genotypic ratio: • Phenotypic ratio:

  27. Dihybrid Crosses • A type of punnett square where parents’ two genotypes are crossed • There are two sets of letters for each parent • Ex: B and P • Parent 1 genotype: BBPp • Parent 2 genptype: Bbpp

  28. Law of Independent Assortment: During gamete formation, the alleles of each gene segregate independently • Basically, the alleles can mix and match

  29. Example: • Parent 1: HHBb • Parent 2: HhBb • Possible parent 1 genotypes • HB, Hb, HB, Hb • Possible parent 2 genotypes • HB, Hb, hB, hb

  30. Find the possible genotypes • Parent 1: RrTT • Parent 2: rrTt • Parent 1: SSPP • Parent 2: Sspp • Parent 1: ggFF • Parent 2: GgFf

  31. Dihybrid Cross Example • Cross RrEE with rrEe • Parent 1 Genotypes • Parent 2 Genotypes

  32. Dihybrid Cross Example • Cross ttHH with TtHh • Parent 1 genotypes: • Parent 2 Genotypes:

  33. Dihybrid Examples • Spots and Curly hair are both dominant. Cross a heterozygous dominant spotted/straight haired dog with a Homozygous dominant spotted/heterozygous curly haired dog

  34. Dihybrid Examples • Yellow flowers and wrinkled seeds are both dominant. Cross a white flower/non wrinkled seed plant with a heterozygous dominant yellow/homozygous dominant wrinkled plant

  35. Dihybrid Example • Widows peaks and nonattached ears are dominant. Cross a homozygous dominant widows peak/attached eared person with a heterozygous dominant widows peak/heterozygous dominant unattached eared person

  36. Other types of inheritance • Incomplete dominance- when the phenotype is between the two traits of the parents • Ex: Red parent RR and white parent rr makes a Rr Pink offspring • Neither allele is completely dominant over the other

  37. Incomplete dominance Example • Black and white are incompletely dominant to each other. Cross a homozygous black cat with a homozygous white cat

  38. Incomplete dominance Example • Red and blue are incompletely dominant. Cross a homozygous red flower with a homozygous blue flower.

  39. Incomplete dominance Example • Blue and yellow are incompletely dominant. Cross a heterozygous green flower with a homozygous blue flower

  40. Incomplete dominance Example • Yellow and red are incompletely dominant. Cross red flower with a heterozygous orange flower.

  41. Other types of inheritance • Codominance- condition in which both alleles for the same gene are fully expressed • Ex: Parent has AA blood type (type A), other parent has BB (type B), offspring get AB and has the AB blood types • You see both alleles the same

  42. Codominance Example • In blood types, A and B are codominant to each other. Cross a Homozygous A type with an Homozygous B type.

  43. Incomplete dominance Example • In blood types, A and B are codominant to each other. Type O is recessive. Cross a homozygous type A blood type with a AB blood type.

  44. Incomplete dominance Example • In blood types, A and B are codominant to each other. Type O is recessive. Cross a heterozygous A blood type with a O blood type

  45. Incomplete dominance example • In dogs, brown and white are codominant to each other. Cross a homozygous brown dog with a homozygous white dog.

  46. Codominance Example • In dogs, brown and white are codominant to each other. Cross a heterozygous brown and white dog with a brown dog

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