Objectives

1. Chapter 8 Section 3 Studying Heredity Objectives • Predictthe results of monohybrid genetic crosses by using Punnett squares. • Applya test cross to determine the genotype of an organism with a dominant phenotype. • Predictthe results of monohybrid genetic crosses by using probabilities. • Analyzea simple pedigree.

2. New Vocabulary • Punnett square • Test cross • Probability • pedigree • Sex-linked gene

3. To predict the genotypes and phenotypes of offspring, Mendel ___________ his crosses and analyzed ________ amounts of data • In 1905, a mathematician named Reginald ___________ devised a _______________ method, called a punnett square, for predicting the outcome of ________________ crosses controlled vast short hand Punnett individual

4. Chapter 8 Section 3 Studying Heredity Punnett Squares A Punnett squareis a diagram that predicts the outcome of a ______________ cross by considering all possible ___________ combinations of gametes in the cross. single allele

5. segregate Remember, the two alleles in a gene _________________ during gamete formation The possible gametes that the female can produce are written along the _________ of the square. The possible gametes that the male can produce are written along the _________ side of the square. Female Y Y top Male y left y

6. Each box inside the square is filled in with two letters obtained by ___________ the allele along the ______ of the box with the allele along the _________ of the box. Female combining top Male Yy Yy side Yy Yy

7. What process is occurring in each box when the gametes combine? fertilization

8. What genotype will all of the possible offspring have? • And the phenotype? Yy yellow

9. Practice! • Cross a two pea plants heterozygous for height… T = tall and t = short Genotype ratio? Phenotype ratio? T t T TT Tt t Tt tt 1TT : 2Tt : 1tt 3 tall : 1 short

10. Practice! • Cross a “female” pea plant heterozygous for seed color and a “male” recessive for seed color… Y = yellow and y = green Genotype ratio? Phenotype ratio? Y y y Yy yy y Yy yy 2Yy : 2yy 2 yellow : 2 green

11. Reduce the ratio 2:2 • Convert this ratio to a fraction • What percent does the fraction represent? 1 : 1 ½ 50%

12. autosomal • The previous crosses were for genes on _________________ chromosomes • Review…what are autosomes? • Punnett squares can also be created for ________ chromosomes • In this case, the alleles must be linked on the _______ or _______ chromosome Your 1st 22 homologous pairs of chromosomes sex X Y

13. Morgan fruit flies • In 1910, Thomas Hunt __________ discovered sex-linked inheritance while studying _______ ________. • In fruit flies, the gene for eye color is linked on the ______ chromosome • If R = red and r = white, determine the eye color and sex for the following genotypes • XRXR = ________________ • XRXr = _________________ • XrXr = __________________ • XRY = __________________ • XrY = __________________ X Red female Red female White female Red male White male

14. recessive X • In humans, red green color blindness is a _____________ trait linked on the _____ chromosome • Determine the following phenotypes… • XCXc = _______________ • XcY = ________________ • XCY = ________________ • The female above does not have color blindness but ____________ the recessive allele Color vision female Color blind male Color vision male carries

15. Practice! XC Xc • Cross a female who is a carrier for colorblindness with a male recessive for color blindness C = normal vision and c = colorblind Genotype ratio? Phenotype ratio? Does a male offspring inherit colorbindness from his mom or dad? Xc XCXc XcXc XCY XcY Y 1 XCXc : 1 XcXc : 1 XCY : 1 XcY 1 c.v. female : 1 c.b. female : 1 c.v. male : 1 c.b. male Mom!...inherits Y from dad

16. Review? • What genotype(s) may a purple pea plant have? • Animal breeders, horticulturists, and others involved in breeding organisms often need to know whether an organism with a dominant phenotype is _______________ or ________________ for a trait. • To determine the genotype, breeders cross the organism with an individual that is _____________ for the trait in a cross called a ________ cross PP or Pp homozygous heterozygous recessive test

17. Test cross P P P p • If the unknown genotype is PP, what color flowers will all of the offspring have? • If the unknown genotype is Pp, what color flowers may the offspring have? p p Pp pp Pp Pp p p Pp Pp Pp pp Purple Purple and white

18. Chapter 8 Section 3 Studying Heredity Outcomes of Crosses • Like Punnett squares, ______________ calculations can be used to predict the results of genetic crosses. • Probabilityis the _________________ that a specific event will occur. • Probability = probability likelihood # of outcomes desired # of outcomes total

19. So if there are five marbles in a jar, and only one is red, what is the probability that you pull a red marble out of the jar? • If you flip a coin, what is the probability that it will land heads up? • If you flip a coin again, what is the probability that it will lands head up? 1/5 1/2 1/2

20. future • So prior events do not affect the outcome of ____________ events • In the following cross… What is the probability that two parents will have a girl? What is the probability that their next child will be a girl? X X X XX XX Y XY XY 1/2 1/2

21. large • The outcomes predicted by Punnett squares are most often seen in ______________ populations…. • Is everyone’s family made up of exactly half girls and half boys? • But a larger population, like the entire _________, is roughly 50:50 or 1:1 no planet

22. multiple same • To determine the probability of ____________ events or events occurring at the _________ time, the probability for each event is _________________ by eachother. • What is the probability that a coin will land heads up four times consecutively? multiplied ½ x ½ x ½ x ½ = 1/16

23. P p • What is the probability that a pea plant offspring will have purple flowers? • What is the probability that a pea plant offspring will be tall? • What is the probability that a pea plant offspring will have purple flowers and tall height? P PP Pp 3/4 p Pp pp 3/4 t T Tt T TT tt t Tt ¾ x ¾ = 9/16

24. Chapter 8 Section 3 Studying Heredity Inheritance of Traits • Geneticists often prepare a ________________, a family history that shows how a trait is inherited over _____________ generations. • Pedigrees are particularly helpful if the trait is a genetic _______________ and the family members want to know if they are _____________ or if their _________________ might get the disorder. • By analyzing a pedigree, we can determine if a trait is ______________ or ______ - linked and ____________ or ______________ pedigree several disorder carriers children autosomal sex dominant recessive

25. Female = circle Male = square Horizontal Line = mating Vertical line = offspring Shaded = affected by the trait Diagonal line = death from trait

26. Autosomal recessive Most genetic disorders are caused by _____________ alleles In this situation, an offspring with ______ recessive alleles has the trait, while each parent is a _________________ What allele combinations might have the other two offspring have? Aa Aa recessive aa two carrier Aa or AA

27. Autosomal Dominant If a trait is dominant, an affected individual will have at least ______ parent who also has the _____________ trait Is the female parent homozygous dominant or heterozygous? How do you know? aa Aa one aa Aa aa dominant heterozygous Not all of the offspring inherit a dominant allele

28. Sex-linked If a trait is sex-linked, it will appear more often in ________ than in females What genotype must all of the females have? What chromosome does a male parent pass onto his son? So is the recessive X-linked gene inherited from the male or female parent? XcY XCXc males XcY XCXc Y female

29. Objective 1 • Predictthe results of monohybrid genetic crosses by using Punnett squares. • If T = tall and t = short… Genotype ratio? Phenotype ratio? T t t Tt tt Tt tt t 2Tt : 2tt 2 tall : 2 short

30. Objective 2 • Applya test cross to determine the genotype of an organism with a dominant phenotype. t t Tt Tt T Dominant Genotype? tt tt t

31. Objective 3 • Predictthe results of monohybrid genetic crosses by using probabilities. If T = tall and t = short, what is the probability that an offspring will inherit short height? T t T TT Tt t Tt tt 1/4

32. Objective 4 • Analyzea simple pedigree. Does this pedigree show an autosomal dominant, autosomal recessive, or sex- linked trait? Autosomal recessive