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Heredity Holt Biology Chapter 8, pgs. 170-171 By Bettina Loell-Hull 1 Anticipatory Set 2 Anticipation Guide: Biology Standard 3a, (7b) (phonotype, genotype, heredity and Punnett Square) Instructions: Before the lesson, read the questions and circle T or F in the left hand column. After lesson, re-read the question and circle T or F in the right hand column. # Before 1 T/F 2 T/F 3 T/F 4 T/F 5 T/F 6 T/F 7 T/F 8 T/F 9 T/F Questions A child receives one allele or version of a trait from each parent. Some children don’t get their genes from their parents because they do not look like their parents. An allele is a version of a gene for a trait. The dominant trait is the expressed version of a gene or the trait that is visible in an individual. The recessive trait will always show in an individual. Genotype refers to the look of an individual. Phenotype refers to the genetic make-up of an individual. If a child has blue eyes and both parents have brown eyes, the baby was adopted. The allele for blond hair is dominant. After T/F T/F T/F T/F T/F T/F T/F T/F T/F Studying Heredity Using the Punnett Square http://www.dailymail.co.uk/news/article-377839/Black-white-twins.html 4 Compare and Contrast the Twins Same parents 1-dark skin (1 or 2 allele(s) for dark skin 2-brown eyes (1 or 2 allele(s) for brown eyes) 1-light skin (2 alleles for light skin) Each parent has 1 brown & 1 blue allele for eye color. Each parent has 1 allele for light & 1 allele dark skin. 3-brown hair (1 or 2 allele(s) for brown hair) Each parent has 1 allele for brown hair & 1 allele for blond hair. fraternal twins 2-blue eyes (2 alleles for blue eyes) 3-blond hair (2 alleles for blond hair) Anticipatory Set 6 Heredity and Eye Color 7 The Punnett Square Calculates the Possibilities of the Children’s Looks Father Mother B B BB b Bb b bb Bb 8 Odds of Dark Hair vs. White Hair 9 10 Homozygous cross and Heterozygous Cross 11 Standard 3a: • Students know how the genotypes of the parents may be expressed as phenotypes in their offspring. • Students relate the ratios that Mendel observed in his crosses to his data and to examples of their own. Phenotype (F1 generation 100 % = 4/4) Phenotype (F2 generation 75% to 25% = 3/1) 12 1. dominant 2. recessive 3. phenotype 4. genotype 5. monohybrid cross 6. homozygous 7. heterozygous 8. allele 9. Punnett square 13 1. Dominant (adjective) • Expressed form of the character trait. • For example the color of a flower may be purple and not white because purple is dominant. 14 2. Recessive (adjective) • The trait that is not expressed when the dominant form of the trait is present. Ex.: In this case, the baby has blue eyes because she has two recessive alleles for blue eyes. 15 3 Phenotype (noun) • A phenotype is a living thing’s appearance or other detectable characteristic that results from the living thing’s genotype and the environment. • For example: the color of a flower or seed 16 4 Genotype (noun) • The entire genetic makeup of an organism- its DNA • Or the combination of genes for one specific trait. •For example, the color of the seed pod is green but the genetic make-up of it is yellow and green. 17 5-Monohybrid Cross (noun) • A cross in which each parent displays a different form of one allele. • For example: seed color (YY or yy) 18 6-Homozygous (adjective) • Describes an individual that has identical alleles for a trait on both gametes. • Example: PP or pp for color of flower. 19 7-Heterozygous (adjective) • Describes an individual that has two different alleles for a trait. • For example, a flower may look purple but has the alleles Pp for flower color. 20 8-Allele (noun) • An allele is one of the alternative forms of a gene that determines a characteristic, such as hair color. Example: the alleles for hair color may be black or blond. 21 9-Punnett Square (noun) • A Punnett square is a graphic representation used to predict the chances that the offspring will inherit an allele for a trait. What are the chances of a yellow offspring if yellow is dominant? 100% 22 1-Dominant A-Describes an individual who has two different alleles for a trait. 2-Recessive B-graphic representation used to predict chances of offspring to inherit allele of a trait C- The trait that is not expressed when the dominant form of the character is present. D- Describes individual with identical alleles for a trait. 3-phenotype 4-genotype 5-monohybrid cross 6-homozygous E-the combination of genes for one 7-heterozygous G- Expressed form of character trait. 8-allele H-A cross in which each parent displays a different form of one character trait. specific trait. F- a thing’s or person’s appearance 9-punnett square I- one of the alternative forms of a gene. Solution to Quiz Video on Punnett Square 1 2 3 4 5 6 7 8 9 G C F E H D A I B Home 24 Video 25 Video on Heredity How to use the Punnett Square to Calculate the Odds of the Phenotype (looks) of Offspring • Gregor Mendel's Rules of Heredity—Demonstration of impact that Parents Genotype has on Offspring’s Phenotype Using Punnett Squares 26 What did we learn from the video? • We learned how to use the Punnett Square to calculate the odds of a certain phenotype in the offspring. • We learned how to create a Monohybrid Cross 1. with homozygous parents 2. with heterozygous parents 1 2 27 Modeling 1 28 Monohybrid Cross – with Homozygous Bunny Parents f F F f F F f f F f Black is dominant F f Black Fur 4/4=1=100% White Fur 0/4=0=0%29 Modeling 2 30 Monohybrid Cross (one trait) – with Heterozygous Bunny Parents F F F F f F f Black is dominant Offspring’s Phenotype f F f f f Black Fur White Fur ¾ = 75% =.75 ¼ = 25% =.25 31 Guided Practice 1 32 Monohybrid Cross – with Homozygous Parents who have blue eyes and brown eyes. b B B b B B b b B b B b Brown is dominant Offspring’s Phenotype Brown Eyes Blue Eyes 4/4 =100% =1 0/4=0%=033 Guided Practice 2 34 Monohybrid cross – with Heterozygous Parents Who both have Brown Eyes. B B B B b B b b B b Brown is dominant bb Offspring’s Phenotype Brown Eyes ¾ =75% =.75 Blue Eyes ¼ =25% =.25 35 Independent Practice 1 36 • • • • • • • Monohybrid cross with homozygous (BB or bb) parents Predict the phenotype of the offspring resulting from a cross of a white haired dog with a black haired dog. Make black hair (B) dominant and white hair (b) recessive. The white dog is homozygous recessive. The black dog is homozygous dominant. Write the gametes that each parent can. contribute as row and column labels. What does the offspring look like? State your answer in %, fraction, and decimals for each phonotype. Monohybrid Cross – with Homozygous Parents (dogs) who have white fur and black fur. Black is dominant Offspring’s Phenotype Black Fur,x/4, %, x.xx White Fur x/4, %, x.xx 38 Monohybrid Cross – with Homozygous Parents (dogs) who have white fur and black fur. b B B b B B b b B b B b Black is dominant Offspring’s Phenotype Black Fur White Fur 4/4 = 100% =1 0/4 =0% =039 Independent Practice 2 40 Monohybrid cross with heterozygous (Bb and Bb) parents • Predict the phenotype of the offspring of a cross of a black haired dog with a black haired dog (black hair is dominant that is why both dogs are black). • Both dogs are heterozygous for hair color (Bb and Bb). • Write the gametes that each parent can contribute as row and column labels. • What does the offspring look like? • State your answer in %, fraction, and decimals for each phonotype. Monohybrid Cross – with Heterozygous Parents (dogs) who both have black fur. Black is dominant Offspring’s Phenotype Black Fur,x/4, %, x.xx White Fur x/4, %, x.xx 42 Monohybrid Cross – with Heterozygous Parents (dogs) who both have black fur. B b B B B B b B b bb b Black is dominant Offspring’s Phenotype Black Fur ¾ =75% =.75 White Fur ¼ =25% =.25 43 End of Lesson 1 44 45 1 Modeling Punnett Squares / Monohybrid Cross (1 traits = fur color) homozygous parents Phenotype (looks) of offspring Fraction Percent Decimal heterozygous parents /4 % /4 % . . Phenotype (looks) of offspring /4 % Fraction Percent Decimal . /4 % . 1. Escape 2. Double Click on document to open in word and see worksheets Release test question: Ch c Ch c Ch Ch Ch c Chc cc Chc Produces offspring that is least likely to survive. 47 48 Resources Types of Learners http://www.chaminade.org/inspire/learnstl.htm Video on Punnett Square and monohybrid crosses with homozygous parents and heterozygous parents. Gregor Mendel's Rules of Heredity— Demonstration of impact that Parents Genotype has on Offspring’s Phenotype Using Punnett Squares Holt Biology, chapter 8, pages 170-171 49