1. Genetics Chapter 8

2. Origins of Genetics Heredity  The passing of characters from parents to offspring Character  Inherited characteristic (ex. flower color) Trait  Single form of a characteristic (ex. purple flower)

3. Genes Control the expression of traits (i.e. flower color)  Have two parts - alleles  One allele is from Mom other from Dad.

4. Alleles Dominant - the expressed allele of the gene  Capital letterEx. P Recessive - the allele that was not expressed  Lower case letterEx. P Homozygous (Homo = same)  Two alleles are the same Ex.PP or pp Heterozygous (Hetero = different)  The alleles are different Ex. Pp

5. Modern Terms Genotype  The set of alleles for a Gene Ex. PP, Pp or pp Phenotype  Physical appearance Ex. Purple or White Flowers  The dominant allele determines phenotype Ex. Pp  Purple Flower or PP  Purple Flower  If both alleles are recessive then the individual will express the recessive phenotype. Ex. pp  White Flower

6. Probability The likelihood that a specific event will occur  Expressed in multiples ways: Fractions½ Percentages 50% Decimals.5 Ratios3:1 or 3 to 1 Probability = # of one kind of possible outcome Total # of all possible outcomes

7. Monohybrid Crosses Cross 1 character – Seed Color Yellow Seeds are dominant – Y Green Seeds are recessive – y Cross a Homozygous Dominant Yellow with a Green. Genotype Ratio: 4Yy Phenotype Ratio: 4 Yellow Probabilities: Being Yellow: 4 out of 4 Being Green: 0 out of 4 Cross: TT X tt YY y y YyYy YyYy

8. Monohybrid Crosses Cross 1 character – Flower Color Purple Flowers are dominant – P White Flowers are recessive – p Cross a Heterozygous with a homozygous recessive Genotype Ratio: 2 Pp; 2 pp Phenotype Ratio: 2 Purple 2 White Probabilities: Being Purple: 2 out of 4 Being White: 2 out of 4 Cross: Pp X pp Pp p p Pppp Pppp

9. Incomplete Dominance Inheritance that is intermediate between two parents  Ex. Snapdragon with red flowers are crossed with a snapdragon with white flowers  a snap dragon with pink flowers is produced.  Neither the allele for red flowers nor the allele for white flowers is dominant.

10. Incomplete Dominance Genotype for red flowers:RR Genotype for white flowers:WW, Genotype for pink flowers: RW. Cross a red with a white. Genotype Ratio: 4 RW Phenotype Ratio: 4 Pink Flowers Probabilities:  Red Flower:  0 out of 4  White Flower  0 out of 4  Pink Flower:  4 out of 4 Cross: RR X WW RR W W RWRW RWRW

11. Incomplete Dominance Genotype for red flowers:RR Genotype for white flowers:WW, Genotype for pink flowers: RW. Cross a pink with a white. Genotype Ratio: 2 RW; 2WW Phenotype Ratio: 2 Pink; 2 White Probabilities:  Red Flower:  0 out of 4  White Flower  2 out of 4  Pink Flower:  2 out of 4 Cross: RW X WW RW W W RWWW RWWW

12. Codominance Case in which both forms of the character are displayed. Ex. The ABO blood groups  Neither I A nor I B are dominant is dominant over the other.  Both are dominant over i.  When both I A and I B are present they are codominant and the individual is type AB

13. Blood Typing iiIBiIBiIAiIAi IBiIBiIBIBIBIB IAIBIAIB IAiIAiIAIBIAIB IAIAIAIA I A I B i IAIBiIAIBi OBABA Blood Types

14. Blood Typing Cross a homozygous type A with a type O Homozygous type A: IAIA Type O:ii Genotype Ratio: 4 IAi Phenotype Ratio: 4 Type A Probabilities: Type A:4 out of 4 Type O:0 out of 4 IAiIAiIAiIAi IAiIAiIAiIAi I A I A X ii IAIA IAIA i i

15. Blood Typing Cross a type AB with a type O Homozygous type A: I A I B Type O:ii Genotype Ratio: 2 I A i; 2 I B i Phenotype Ratio: 2 Type A 2 Type B Probabilities: Type A:2 out of 4 Type B:2 out of 4 IBiIBiIAiIAi IBiIBiIAiIAi I A I B X ii IAIA IBIB i i

16. Sex-Linked Traits Body cell has 46 chromosomes -  44 autosomes, 2 sex chromosomes. Gamete (egg/sperm) has 23 chromosomes –  22 autosomes, 1 sex chromosome Sex-Linked Gene  A gene located only on the X or Y  Most are carried on the X chromosome  Males have only one X chromosome  Male who carries a recessive allele on the X chromosome will exhibit the sex-linked condition

17. Condition that impairs the blood’s ability to clot  A sex-linked trait  Carriers and victims contain the recessive allele on their X-chromosomes  Only females can be carriers  X H X h  Because males only have one X chromosome  Males CAN NOT be carriers only victims. Hemophilia (Heme: blood, philia: liking of)

18. Sex Linked Traits XHYXHYXhYXhY XHXHXHXH XHXhXHXh X H Y XX H X h XhXHXhXH XHYXHY The normal gene: X H The hemophilia gene:X h Cross a normal male with a carrier female Genotype Ratio: 1 X H X h : 1 X H X H : 1 X h Y: 1X H Y Phenotype Ratio: 1 norm. female: 1 carrier female: 1 norm. male: 1 hemophilic male Probabilities Normal Female: 1 out of 2 Carrier Female: 1 out of 2 Normal Male: 1 out of 2 Hemophilic male: 1 out of 2

19. Sex Linked Traits XhYXhYXHYXHY XhXhXhXh XHXhXHXh X h Y XX H X h XHXhXHXh XhYXhY The normal gene: X H The hemophilia gene:X h Cross a hemophilic male with a carrier female Genotype Ratio: 1 X H X h : 1 X h X h : 1 X H Y: 1X h Y Phenotype Ratio: 1 carrier female: 1 hemophilic female: 1 norm. male: 1 hemophilic male Probabilities Hemophilic Female: 1 out of 2 Carrier Female: 1 out of 2 Normal Male: 1 out of 2 Hemophilic male: 1 out of 2

20. Genetic Disorders Sickle Cell Anemia  Recessive disorder among African Americans  Caused by a mutated allele that produces a defective hemoglobin protein. Hemoglobin in RBC’s bind and transport oxygen through the body

21. Genetic Disorders Cystic Fibrosis  Fatal hereditary recessive disorder among Caucasians.  Clogging of the airways and lungs with thick mucus and the blockage of ducts of the liver and pancreas.  There is no known cure.

22. Genetic Disorders Albinism  Recessive  Body is unable to produce an enzyme necessary to make melanin. Melanin is a pigment that gives color to hair, skin and eyes

23. Pedigrees A family history that shows how a trait is inherited over several generations Helps to track down the carriers (heterozygotes) of recessive disorders. Reading Pedigrees  A shaded box –affected male …………  A shaded circle- affected female……….  A clear box- normal male…………..  A clear circle- normal female………...

24. Pedigree Practice A man and woman marry. They have five children, 2 girls and 3 boys. The mother is a carrier of hemophilia, an X-linked disorder. She passes the gene on to two of the boys who died in childhood and one of the daughters is also a carrier. Both daughters marry men without hemophilia and have 3 children (2 boys and a girl). The carrier daughter has one son with hemophilia. One of the non-carrier daughter’s sons marries a woman who is a carrier and they have twin daughters. What is the percent chance that each daughter will also be a carrier? ? I II III IV ? Legend: Hemophilic Male: ……… Hemophilic Female: …... Normal Female: ……… Normal Male: ………

25. Pedigree Practice XHXhXHXh XHYXHY XhYXhYXHXhXHXh XhYXhYXHXHXHXH XHYXHYXHYXHYXHYXHY XhYXhYXHYXHYXHXHXHXH XHXhXHXh XHYXHYXHYXHYXHXHXHXH Probability of X H X h ? The non-carrier normal daughter in the 2 nd generation must have a genotype of X H X H her normal husband must have the genotype X H Y; therefore, it is not possible for any of their children to have hemophilia or be a carrier of the trait.

26. Pedigree Practice XHXhXHXh XHYXHY XhYXhYXHXhXHXh XhYXhYXHXHXHXH XhYXhYXHYXHYXHYXHY XhYXhYXHYXHYXHXHXHXH XHXhXHXh XHYXHYXHYXHYXHXHXHXH Probability of X H X h ? However, when their normal son (genotype X H Y) marries a woman who is a carrier of the trait (genotype X H X h ), then the probability that each of his twins will be a carrier is 1 out of 2 (50%). XhYXhYXHYXHY XHXhXHXh XHXHXHXH XHXhXHXh XHYXHY