Name______Date______

Genetics Notes Continued…

I. Mendel’s Laws

1. Law of Dominance

a) Each trait is controlled by 2 factors, one factor (dominant ) may mask the other factor (recessive ) preventing it from having an effect

2. Law of Segregation

a) Each allele a person has separates into different gametes

  1. Ex. Ww – one W goes in one sperm and the other w goes into another sperm

3. Law of Independent Assortment

a) Gene pairs (homologous) will separate randomly into gametes (metaphase I of meiosis)

II. Dihybrid Crosses

1.A dihybrid cross allows us to predict possible outcomes of offspring that will have 2 traits simultaneously.

Ex: what would you get if you crossed a Brown-haired brown-eyed male with a blonde-haired blue-eyed female? How many of the children would have brown hair and brown eyes? Brown hair and blue eyes? Blonde hair and brown eyes? Blonde hair and blue eyes?

Step 1: Determine the parent genotypes ______x ______

Step 2: Determine the possible gametes______x ______

Step 3: Set up your punnett square and put each of the parents gametes in right spot

Step 4: Fill out punnett square and determine genotypic ration & phenotypic ratio

PRACTICE:

Genotypic Ratio: ______Phenotypic Ratio: ______

1.Mickey Mouse is heterozygous for Round ears and homozygous for Black eyes. Minnie Mouse also is homozygous for Floppy ears and heterozygous for Black eyes. Determine genotype and phenotype ratios. (B=black, b=brown, R=round, r= floppy.)

a) What are the parental genotypes? ______x______

b) What are the allele combinations to be passed down? ______x ______

c) Set up punnett square

d) Genotypic Ratio: ______Phenotypic Ratio: ______

III. Different types of Inheritance

  1. Incomplete Dominance:
  2. Heterozygous phenotype is an intermediate phenotype between the two homozygous phenotypes.
  3. Two alleles are blended
  4. Ex) Four O’clock Flowers
  5. Red + White = Pink
  1. Codominance:
  2. Neither trait is dominant instead, both traits are shown (No Blending)
  3. Ex) Roan Cows
  4. Red + White = RED AND WHITE
  1. Multiple Alleles:
  2. Multiple alleles – 3 or more alleles
    that control a trait
  3. Sex-linked traits:
  4. Traits located on the sex chromosomes (X or Y)
  5. X linked: gene is located on the X chromosomes
  6. Y linked: gene is located on the Y chromosome

IV. Pedigrees

a. Shows history of a trait in a family

  1. Allows researchers to analyze traits within a family

Example Pedigree:

*The squares represent males

* The circles represent females

* The shaded are represents the trait being analyzed

* The unshaded shapes represent people who do not have the trait

This pedigree is following the presence of blonde hair through 3 generations. Determine the genotypes for all of the family members and write them below each shape!