Mendel's Laws of Inheritance

Principles of Inheritance

Mendel's Laws

• Law of Segregation: Each pair of alleles separates from each other during gamete formation, resulting in each gamete receiving only one allele.
• Law of Independent Assortment: Alleles for different genes are sorted independently of each other during gamete formation.
• Law of Dominance: One allele can be dominant over another allele, resulting in the dominant allele being expressed in the phenotype.

Incomplete Dominance

• When one allele is not completely dominant over another allele, resulting in a blend of the two alleles in the phenotype.
• Example: Red flowers (R) and white flowers (r) producing pink flowers (Rr) when crossed.

Codominance

• When both alleles have an equal effect on the phenotype, resulting in both alleles being expressed.
• Example: Blood type, where both A and B alleles are expressed in the AB blood type.

Linkage

• The tendency of certain genes to be inherited together due to their proximity on the same chromosome.
• Genes that are linked do not assort independently, violating the Law of Independent Assortment.

Sex-Linked Inheritance

• Traits that are determined by genes located on the sex chromosomes (X and Y).
• Sex-linked traits are more common in males, as they only have one X chromosome.
• Examples: Color blindness and hemophilia.

Multiple Alleles

• When a gene has more than two alleles.
• Example: ABO blood type, which has three alleles: A, B, and O.

Polygenic Inheritance

• Traits that are determined by multiple genes.
• Each gene has a small effect on the phenotype, resulting in a continuous range of phenotypes.
• Examples: Height, skin color, and intelligence.

Chromosomal Inheritance

• Traits that are determined by the number or structure of chromosomes, rather than individual genes.
• Examples: Down syndrome (trisomy 21), Turner syndrome (45,X), and Klinefelter syndrome (47,XXY).

Mendelian Disorders

• Genetic disorders that follow Mendel's Laws of Inheritance.
• Examples: Cystic fibrosis, sickle cell anemia, and Huntington's disease.
• These disorders are typically caused by mutations in a single gene.

Mendel's Laws

• Each pair of alleles separates during gamete formation, resulting in each gamete receiving only one allele (Law of Segregation).
• Alleles for different genes are sorted independently of each other during gamete formation (Law of Independent Assortment).
• One allele can be dominant over another allele, resulting in the dominant allele being expressed in the phenotype (Law of Dominance).

Incomplete Dominance and Codominance

• When one allele is not completely dominant over another allele, resulting in a blend of the two alleles in the phenotype (Incomplete Dominance).
• Example: Red flowers (R) and white flowers (r) producing pink flowers (Rr) when crossed.
• When both alleles have an equal effect on the phenotype, resulting in both alleles being expressed (Codominance).
• Example: Blood type, where both A and B alleles are expressed in the AB blood type.

Linkage and Sex-Linked Inheritance

• The tendency of certain genes to be inherited together due to their proximity on the same chromosome (Linkage).
• Genes that are linked do not assort independently, violating the Law of Independent Assortment.
• Traits that are determined by genes located on the sex chromosomes (X and Y) (Sex-Linked Inheritance).
• Sex-linked traits are more common in males, as they only have one X chromosome.

Multiple Alleles and Polygenic Inheritance

• When a gene has more than two alleles (Multiple Alleles).
• Example: ABO blood type, which has three alleles: A, B, and O.
• Traits that are determined by multiple genes (Polygenic Inheritance).
• Each gene has a small effect on the phenotype, resulting in a continuous range of phenotypes.
• Examples: Height, skin color, and intelligence.

Chromosomal and Mendelian Disorders

• Traits that are determined by the number or structure of chromosomes, rather than individual genes (Chromosomal Inheritance).
• Examples: Down syndrome (trisomy 21), Turner syndrome (45,X), and Klinefelter syndrome (47,XXY).
• Genetic disorders that follow Mendel's Laws of Inheritance (Mendelian Disorders).
• Examples: Cystic fibrosis, sickle cell anemia, and Huntington's disease.
• These disorders are typically caused by mutations in a single gene.