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Warm-up (use pencil today)

Warm-up (use pencil today). 1.What type of cross does the visual below represent? (Hint: see word wall terms) 2. How many traits are being crossed? 3. What are the genotypes of the traits being crossed? 4. What words from the word wall represent the parent genotypes?. PART 2.

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Warm-up (use pencil today)

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  1. Warm-up (use pencil today) 1.What type of cross does the visual below represent? (Hint: see word wall terms) 2. How many traits are being crossed?3. What are the genotypes of the traits being crossed?4. What words from the word wall represent the parent genotypes?

  2. PART 2

  3. Mendel’s experimentation with peas continued: • Mendel performed another set of crosses in which he used peas that differed from each other in two traits rather than only one. • A cross involving two pairs of contrasting traits is called a dihybrid cross (because di means “two”). example: seed shape (smooth vs. wrinkled) and seed color (yellow vs. green). • Mendel wanted to find out if the two traits would stay together in the next generation (do they influence one another). • After Mendel experimented with the dihybrid crosses, he found that alleles sorted independently. “Mendel’s Law of Independent Assortment”: two alleles for different traits can segregate independently during the formation of gametes.

  4. How do we use a Punnett square to conduct Dihybrid Crosses? We start by determining the possible gamete combination of each parent’s genotype.

  5. #1. Possible Gametes: To determine the number of different gametes a parent can have, we use the acronym FOIL (First – Outer – Inner – Last) with the pair of traits. rrEe rE re rE re There are 2 possible gametes: rE and re

  6. #2. Possible Gametes: To determine the number of different gametes a parent can have, we use the acronym FOIL (First – Outer – Inner – Last) with the pair of traits. RREe RE Re RE Re There are 2 possible gametes: Re and RE

  7. #3. Possible Gametes: To determine the number of different gametes a parent can have, we use the acronym FOIL (First – Outer – Inner – Last) with the pair of traits. RREE RE RE RE RE There is 1 possible gamete: All gametes are RE

  8. Determine the different types of gametes Hint: Use the FOIL method. Parent genotype Number of gamete variations TTYY = one (TY) #4. TtYY = #5. two (TY and tY) TtYy #6. = four (TY,Ty, tY, ty,)

  9. Determining Gametes: What are the different possible gametes combinations for these parents (R=round, r=wrinkled, T=tall, t=short) ? RRTT x RrTt RT RT, Rt, rT, rt There are 4 total different gametes

  10. #7. Determine the possible gametes and offspring by completing the cross below (R=round, r=wrinkled, T=tall, t=short). RRTT x RrTt RT Rt rT rt RRTT RRTt RrTT RrTt RT Genotypic ratio? 4 RRTT 4 RRTt 4 RrTT 4 RrTt RT RRTT RRTt RrTT RrTt Phenotypic ratio? RRTT RRTt RrTT RrTt RT 16 Round/Tall RRTT RRTt RT RrTT RrTt

  11. #8. Determine the possible gametes and offspring by completing the cross below (R=round, r=wrinkled, T=tall, t=short). rrTt x RRTt RT Rt RT Rt RrTT RrTt RrTT RrTt rT Genotypic ratio? 4 RrTT 8 RrTt 4 Rrtt RrTt Rrtt RrTt Rrtt rt Phenotypic ratio? RrTT RrTt RrTT RrTt rT 12 Round/Tall 4 Round/short rt RrTt Rrtt RrTt Rrtt

  12. #9. Determine the possible gametes and offspring by completing the cross below (R=round, r=wrinkled, T=tall, t=short). RrTt x RrTt RT Rt rT rt Genotypic ratio? RRTT RRTt RrTT RrTt RT 1 RRTT 2 RRTt 2 RrTT 4 RrTt 1 RRtt 2 Rrtt 1 rrTT 2 rrTt 1 rrtt RRTt RRtt RrTt Rrtt Rt rT RrTT RrTt rrTT rrTt Phenotypic ratio? 9 Round/Tall 3 Round/short 3 wrinkled/Tall 1 wrinkled/short rt RrTt Rrtt rrTt rrtt

  13. RESPONSE BOARDASSESSMENTARE YOU READY?

  14. Warm-up 1-10-13 • According to the table above which of the following • phenotypes would probably occur in all the offspring • from the parents shown above? • Solid gray fur c. Green eyes • Striped gray fur d. Blue eyes

  15. A pea plant with the genotype TtWW is crossed with a pea plant with the genotype ttWw. How many different genotypes can be expressed in the offspring? • 1 • 2 • 3 • 4

  16. Two cats heterozygous for short hair and tabby striping mate. Short hair is dominant over long hair. Tabby striping is dominant over plain coat. 1. What is the phenotypicratio? 9 Short/Tabby 3 Short/Plain 3 long/Tabby 1 long/plain 2. What is the probability of producing a long haired, tabby cat? 3 out of 16

  17. Online Dihybrid Cross Practice http://biology.clc.uc.edu/courses/bio105/geneprob.htm

  18. Why Did Mendel Conclude That The Inheritance of one Trait is Independent of Another? Phenotype Ratio: 9 yellow/smooth 3 yellow/wrinkled 3 green/smooth 1 green/wrinkled Because it’s the only way to explain the pattern of inheritance.

  19. What Works for Peas Also Works for Humans Consider a cross between parents heterozygous for both deafness and albinism. This is the same 9:3:3:1 ratio seen for Mendel’s cross involving pea color and shape.

  20. Going Beyond Dominant and Recessive There are always exceptions to the rule…

  21. + + + + +

  22. Some alleles are related through Incomplete Dominance WW white a cross between organisms with two different phenotypes produces hybrid offspring with a third phenotype that is a blending of the parental traits. 

  23. Codominance A. A cross between two different phenotypes produces a third phenotype where both traits appear “together” in a hybrid offspring. B. A. Cross between a homozygous red flower and a homozygous white flower. B. Cross between homozygous IA blood type and homozygous IB blood type.

  24. Codominance cont’d Cross between a homozygous black horse and a homozygous white horse. W W B B

  25. Incomplete or Codominant? +

  26. Incomplete or Codominance? X

  27. Polygenic Inheritance – when a single trait is influenced by many genes

  28. Polygenic Inheritance Examples: Height Hair texture Skin color eye color

  29. Multiple Alleles Many genes are present in 3 or more alleles (versions). This is known as multiple alleles. The human ABO blood group is determined by three alleles (IA, IB, and i) of a single gene.

  30. Human Blood Types

  31. Sex-Linked Traits Characteristics that are inherited from genes found on the sex chromosomes.

  32. Sex-Linked Traits • Sex Determination • Females – XX • Males – XY • Almost all sex-linked traits are found on the X chromosome • Y chromosome contains very few genes and is mainly involved in sex determination

  33. Intro to Human a Karyotype

  34. Normal Male and Female Karyotypes See page 341 in your biology textbook In a human karyotype, the first 22 pairs of chromosomes are the autosomes. The 23rd pair of chromosomes are the sex chromosomes

  35. Examples of X-linked traits: 1. Color Blindness 2. Hemophilia 3. Muscular Dystrophy

  36. A person with normal color vision sees a number seven in the circle above. Those who are color blind usually do not see any number at all. Colorblindness

  37. RED-GREEN COLORBLINDNESS: People with red-green color blindness see either a three or nothing at all. Those with normal color vision see an 8. Colorblindness

  38. Carrier – person who has one recessive allele and one dominant allele for a trait or heterozygous for that trait. • Example Hemophiliac carrier XHXh Colorblind carrier XCXc http://webexhibits.org/causesofcolor/2.html

  39. Sex-linked punnett square Question: What is the probability that a carrier female and a colorblind male will have a girl who is colorblind (c = colorblind, C = normal)? Xc Y XC Xc

  40. Human Pedigree See page 342-343 in your biology textbook

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