1. Principles of Heredity Chapter 8

2. Gregor Mendel Father of Genetics –1860’s Austrian Monk –Made the 1 st detailed investigation of how traits are inherited using pea plants –Found that traits could be predicted –Established the “Six Principles of Genetics”

3. Six Principles of Genetics 1.Traits of an organism pass from parent to offspring 2.Gene pairs determine traits 3.Organisms inherit genes in pairs; one from each parent

4. Six Principles of Genetics (cont) 4.The 2 members of the parents gene pairs separate at random. 5.Genes are dominant or recessive. When paired, a dominant gene hides the effect of a recessive gene 6.The gene for a particular trait separate independently of genes from other traits.

5. Vocabulary Heredity –The passing of traits from parent to offspring Genetics –The study of inheritance

6. Vocabulary Gene –A unit/section of genetic material (DNA) which determines a trait A pair of homologous chromosomes A gene locus A pair of alleles Three pairs of genes Location of gene on the chromosome

7. Vocabulary Allele –One of 2 or more possible forms of a gene (a specific version of a gene) –Ex: red, brown, black, blonde are the alleles for hair color A pair of homologous chromosomes A gene locus A pair of alleles Three pairs of genes Location of gene on the chromosome

8. Vocabulary Dominant –Shown as a capital letter, it is the expressed trait (ex: R) Recessive –Shown as a lowercase letter, it is the over-ridden trait; only shows if paired (ex: r) Example: –R is dominant over r

9. Vocabulary Genotype –An organisms genetic combination of alleles –Expressed as letters –EX: RR, Rr, rr Phenotype –How an organism looks –Its outward appearance –Ex: red or white flowers

10. Vocabulary Homozygous (Purebred) –contains two matching alleles Example Genotype: TT, tt Heterozygous (Hybrid) –Contains two different alleles Example Genotype: Tt

11. Vocabulary Autosome- any non–sex determining chromosome Sex Chromosome -Either of a pair of chromosomes, usually designated X or Y, in the germ cells of most animals and some plants, that combine to determine the sex and sex-linked characteristics of an individual, with XX resulting in a female and XY in a male in mammals.

12. Punnett Squares Method used to determine offspring ratios of genotypes and phenotypes Male genotype Female genotype

13. Steps to completing a simple Punnett Square 1.Draw a square and divide into 4 boxes 2.Place the proper alleles on the top and side of the box 12 34 AAa a AA x aa

14. Steps to completing a simple Punnett Square To fill in offspring, use the letter above and beside each square –Phenotypic ratio: 4:0 (4 dominant : 4 recessive) –Genotypic ratio: 0:4:0 (0 dominant : 4 heterozygous: 0 recessive) –When the type of dominance changes, so do your ratio outcomes.AAa a AAa a AaAa AaAa

15. Simple Dominance F1 Cross: The trait being studied is round seeds (dominant) and wrinkled seeds (recessive) GenotypePhenotype RR=____RR= ______ Rr=____Rr= _______ rr=____rr= ________

16. Simple Dominance F2 Cross: The trait being studied is round seeds (dominant) and wrinkled seeds (recessive) GenotypePhenotype RR=____RR= ______ Rr=____Rr= _______ rr=____rr= ________

17. Exceptions to Mendelian Genetics Examples: Incomplete Dominance Co-dominance Polygenic Traits Multiple Alleles Sex-linked traits Epistasis

18. Incomplete Dominance –Results when the heterozygous genotype produces a phenotype somewhere in- between the parents (MIXTURE/BLEND) –Example: snapdragon flowers (Aa)

19. Incomplete Dominance Practice In some dragonflies, crossing a red wing dragonfly with a blue wing dragonfly can produce purple wings in their offspring. P1- Cross a homozygous red wing with a homozygous blue wing. P2- cross 2 of their offspring.

20. Co-dominance Results when genes produce a phenotype in which BOTH TRAITS ARE PRESENT Example: type AB blood CODOMINANCE: both A and B antigens appear on red blood cell

21. Roan Cattle: Incomplete or Co-dominance?

22. Co-dominance Practice Some dragonflies having red or blue bodies can produce offspring that are red and blue spotted. P1- Cross a homozygous red to a homozygous blue dragonfly. P2 cross 2 of their offspring.

23. Multiple Alleles Sometimes there are more than two alleles for a given trait. The ABO blood types have three possible alleles. Each person will have TWO of those alleles. A and B both dominate the O allele. The A and B alleles are co- dominant, they are both expressed.

24. Blood Typing Practice Cross 2 individuals that have AB blood type. Cross 2 individuals one with the OO blood type and the other with AO.

25. Sex-linked Traits Traits whose genes are found on the sex chromosomes (either the X or Y chromosomes) Example: color blindness Can you read this?

26. Sex-linked Traits: Color Blindness The allele for color blindness is carried on the X chromosome. A male is more likely to be color blind because he only receives one copy of the X chromosome, where that allele is carried. A female may be carrier of color blindness, but will not exhibit color blindness unless she has both alleles for the trait. How could a female become color blind?

27. Dihybrid Cross involves a study of inheritance patterns for organisms differing in TWO traits. Mendel invented the dihybrid cross to determine if different traits of pea plants, such as flower color and seed shape, were inherited independently.

28. Dihybrid Cross Mendel tested TWO traits: pod shape and color at the same time! Y = yellow pod y = green pod S = round S = wrinkled Dihybrid cross always produces a 9:3:3:1 ratio! ?

29. controlled by two or more than two genes (usually by many different genes) at different loci on different chromosomes.genes loci chromosomes Examples : height, skin color and weight. Polygenic Traits Polygenes allow a wide range of physical traits. For instance, height is regulated by several genes so that there will be a wide range of heights in a population. Polygenestraits genes population

30. Epistasis The masking of the phenotypic effect of alleles at one gene by alleles of another gene A gene is said to be epistatic when its presence suppresses the effect of a gene at another locus. Epistatic genes are sometimes called inhibiting genes because of their effect on other genes

31. Epistasis Cont. Epistasis occurs in all of the following scenarios: Whenever two or more loci interact to create new phenotypes. Whenever an allele at one locus masks the effects of alleles at one or more other loci. Whenever an allele at one locus modifies the effects of alleles at one or more other loci.

32. Product Rule https://www.cdli.ca/courses/biol3201/unit03/unit03_org01_ilo10/productrule.html Product Rule is a way to mathematically, using Algebra, to calculate the offspring possibilities.

33. Pedigree 1 Establish a key for your pedigree chart. You will need different shapes for men and women. You will also need to show what different colors and shades represent on your chart. Usually people who are affected by a gene are shaded one color, people who are carriers of a gene are shaded partially colored and people who are unaffected by a gene are left empty. 2 Put the shapes that represent the eldest members of the family at the top of the chart. If these eldest members are married or had children together, connect them with a horizontal line.

34. Pedigree (cont) 3 Insert the shapes of each generation below the shapes for the previous generation. When people in the family have children, draw the shapes of their mates next to them and connect these two people with a horizontal line. Under these two parents, make a long horizontal line with branching vertical lines for each of the children. Insert the shapes for the children at the bottom of the branching lines. Connect this horizontal line with the horizontal line that connects the parents. 4 Shade in the shapes based on how the gene affects each of the family members. Use the key that you established in Step 1 to do this.

35. Pedigree example