Mendel's Law of Inheritance

Mendel's Law of Inheritance

Segregation

• Definition: The law of segregation states that during the formation of gametes, the alleles for a gene separate from each other.
• Key Points:
  • Each parent contributes one allele for each trait.
  • This results in offspring that inherit one allele from each parent.
  • Demonstrated through monohybrid crosses (e.g., TT x tt producing Tt and tt individuals).

Independent Assortment

• Definition: The law of independent assortment states that alleles of different genes assort independently of one another during gamete formation.
• Key Points:
  • Applies to genes located on different chromosomes or far apart on the same chromosome.
  • Demonstrated through dihybrid crosses (e.g., AaBb parents producing AB, Ab, aB, ab offspring).
  • Results in a variety of genetic combinations in offspring.

Dominance

• Definition: The principle of dominance indicates that some alleles are dominant over others and can mask the presence of recessive alleles.
• Key Points:
  • Dominant allele: Expressed in the phenotype even if only one copy is present (e.g., T in Tt).
  • Recessive allele: Only expressed in the phenotype when two copies are present (e.g., t in tt).
  • Complete dominance (dominant completely masks recessive) vs. incomplete dominance (both alleles influence the phenotype) and codominance (both alleles expressed, e.g., AB blood type).

Mendel's Law of Segregation

• Alleles for a gene separate during gamete formation
• Each parent contributes one allele
• Demonstrated with monohybrid crosses: TT x tt producing Tt and tt individuals

Mendel's Law of Independent Assortment

• Alleles of different genes sort independently during gamete formation
• Applies to genes on different chromosomes or far apart on the same chromosome
• Demonstrated with dihybrid crosses: AaBb parents producing AB, Ab, aB, ab offspring

Principle of Dominance

• Some alleles are dominant, masking recessive alleles
• Dominant allele: expressed even with one copy (e.g., T allele in Tt)
• Recessive allele: only expressed with two copies (e.g., t allele in tt)
• There are different types of dominance:
  • Complete dominance: dominant completely masks recessive
  • Incomplete dominance: both alleles influence the phenotype
  • Codominance: both alleles are expressed (e.g., AB blood type)