Genetic Genetic VariationVariation

Vocabulary You Should Know:

• Dominant• Recessive• Homozygous• Heterozygous• Genotype• Phenotype• Monohybrid Cross (punnett squares)

Bio book Chapter 11, pgs. 262-269

Laws of Genetics• Principle of Segregation – Genes (1 from each

parent) are separated from each other when gametes form (meiosis).

• Principle of Independent Assortment - Alleles for different genes separate independently of one another when gametes form (meiosis).

• Principle of Dominance – Some alleles are dominant & others are recessive.

These laws account for the variations in inherited characteristics.

Bio book Chapter 11, pgs. 265-271

Mendelian Genetics ReviewMendelian Genetics Review• Gregor Mendel studied biological inheritance

with ____ plants. • ______ determine traits.• Different forms of a gene: ______• The Principle of Dominance states that some

alleles are _________& others are ________.• The Principle of Segregation states that during

gamete formation, ______ segregate from each other so that each gamete carries only a ______ copy of each ____.

peaGenes

alleles

dominant recessive

allelessingle

gene

...There are Exceptions to Every Rule!...There are Exceptions to Every Rule!• Genetics is not as simple as just dominant or

recessive• Some alleles are neither dominant nor recessive• Majority of genes have more than 2 alleles• Many traits are controlled by more than 1 gene

• 2 traits combine to make a 3rd trait. Where 1 allele is not completely dominant over another

• Ex: some flowers. Red + White = Pink

Incomplete Dominance Incomplete Dominance Bio book pg. 272

• Both traits appear at the same time. Where both alleles of a gene contribute to the phenotype of the organism

• Ex: Speckled black & white chickens, roan colored horses

CodominanceCodominanceBio book pg. 272

• 3 or more alleles of the same gene• Ex: coat color in Labrador retrievers A/B/O/AB

blood type

Multiple Alleles Multiple Alleles Bio book pg. 273

Blood TypeBlood Type• Multiple Alleles: A, B, AB, O• Codominance: AB

Bio book pg. 344-345

• Trait controlled by 2 or more genes• Ex: Skin color

Polygenic TraitsPolygenic TraitsBio book pg. 273

• Trait controlled by 2 or more genes• Ex: Eye color

Polygenic TraitsPolygenic TraitsBio book pg. 273

• Characteristics of any organism are determined not only by their inherited genes.

• Characteristics are determined by the interaction between the genes & the environment

• Genes provide a plan for development, but how that plan unfolds also depends on the environment

Genetics & the EnvironmentGenetics & the Environment

Soil Type

NutritionSunlight

Climate

Drug Use

Resources

Injuries

Surgery

Medicines

TemperatureHygiene

Bio book pg. 274

Bio book pg. 341

Pedigree ChartBio book pg. 342-343