1 Joke of the Day Mendels Laws 2

1 Joke of the Day:

Mendel’s Laws 2

3 Law of Dominance Some alleles are dominant and others are recessive Example: - Brown Hair is dominant over blonde. copyright cmassengale

Law of Dominance 4 copyright cmassengale

Law of Segregation 5 In Gametes (eggs or sperm), two alleles responsible for a trait separate from each other. Alleles are then "recombined" at fertilization, producing the genotype for the traits of the offspring.

Applying the Law of Segregation 6 copyright cmassengale

7 Law of Independent Assortment Genes for different traits can segregate independently during the formation of gametes. (Genes don’t influence each other) copyright cmassengale

Principle of Probability The likelihood that a particular event will occur Can be used to predict the outcomes of genetic crosses.

9 Dihybrid Cross: (2 factors) A punnett square that tracks the inheritance of two traits. copyright cmassengale

Dihybrid Cross 10 Traits: Seed shape & Seed color Alleles: R round r wrinkled Y yellow y green Rr. Yy RY Ry r. Y ry x Rr. Yy RY Ry r. Y ry All possible gamete combinations copyright cmassengale

Dihybrid Cross 11 RY RY Ry r. Y ry copyright cmassengale Ry r. Y ry

Dihybrid Cross 12 RY RY RRYY Ry RRYy r. Y Rr. YY ry Rr. Yy Ry r. Y ry RRYy Rr. YY Rr. Yy RRyy Rr. Yy Rryy copyright cmassengale Rr. Yy rr. YY rr. Yy Rryy rr. Yy rryy Round/Yellow: 9 Round/green: 3 wrinkled/Yellow: 3 wrinkled/green: 1 9: 3: 3: 1 phenotypic ratio

Dihybrid Cross 13 Round/Yellow: 9 Round/green: 3 wrinkled/Yellow: 3 wrinkled/green: 1 9: 3: 3: 1 copyright cmassengale

14 Special Genetic Cases: copyright cmassengale

Incomplete Dominance 15 Definition: One allele is not completely dominant over another. Red + copyright cmassengale White = Pink

Incomplete Dominance 16 A case in which one allele is not completely dominant over another allele Example: Flower red (rr) x white (ww) rr = red flower ww = white flower w r r copyright cmassengale w

Incomplete Dominance 17 Trait: Flower Color Red (R): Dominant White (R): Dominant Homozygous Dominant Red (rr) X Homozygous Dominant White (ww) w w rw rw r copyright cmassengale 100% rw = Pink (Heterozygous Pink)

Codominance 18 Definition: Both alleles contribute to the phenotype of the organism. Examples: Roan Cattle and Speckled Chickens copyright cmassengale

19 Codominance Problem Speckled Chicken Example: Homozygous male Black (BB) x Homozygous female White (WW) B W BW W copyright cmassengale BW BW 100% BW = Speckled (Heterozygous Speckled)

20 Another Codominance Problem • Example: male heterozygous (BW) x female heterozygous (BW) B B W copyright cmassengale W BB BW BW WW 1/4 = BB 1/2 = BW

21 Sex-linked Traits copyright cmassengale

Sex-linked Traits 22 Traits (genes) located on the sex chromosomes Sex chromosomes are X and Y XX genotype for females XY genotype for males Many sex-linked traits carried on X chromosome copyright cmassengale

Sex-linked Traits 23 Example: Eye color in fruit flies Sex Chromosomes fruit fly eye color XX chromosome - female copyright cmassengale Xy chromosome - male

Sex-linked Trait Problem 24 Example: Eye color in fruit flies (red-eyed male) x (white-eyed female) X RY x X r Remember: the Y chromosome in males does not carry traits. RR = red eyed Xr Rr = red eyed rr = white eyed XY = male XX = female XR Y copyright cmassengale Xr

Sex-linked Trait Solution: 25 Xr XR XR Y Xr Y copyright cmassengale Xr Xr XR Xr Xr Y 50% red eyed female 50% white eyed male

Female Carriers 26 copyright cmassengale