Inheritance patterns explain how traits are passed from parents to offspring. These patterns are governed by Mendelian and non-Mendelian principles.
Mendelian Inheritance
Overview:
Based on Gregor Mendel's studies on pea plants.
Involves traits controlled by single genes on autosomal chromosomes.
Key Laws:
Law of Segregation:
Individuals possess two alleles for each gene, one inherited from each parent.
These alleles segregate during gamete formation, ensuring each gamete carries only one allele for each gene.
Law of Independent Assortment:
The alleles of different genes assort independently during gamete formation, leading to various allele combinations in the offspring.
Modes of Inheritance:
Autosomal Dominant:
A single copy of the dominant allele is enough to express the trait.
Offspring have a 50% chance of inheriting the trait if one parent is affected.
Autosomal Recessive:
Two copies of the recessive allele are needed to express the trait.
There's a 25% chance that offspring will express the trait if both parents are carriers.
X-Linked Dominant:
Dominant allele is on the X chromosome.
Males (XY) have a 50% chance of inheriting from an affected mother; females (XX) have a 50% chance if the father is affected, and up to a 75% chance if both parents are affected.
X-Linked Recessive:
Recessive allele is on the X chromosome.
Males are more likely to express the trait, while females need two copies of the allele.
Non-Mendelian Inheritance
Overview:
Represents more complex genetic interactions that do not adhere to Mendel's laws.
Types:
1.Codominance:
Both alleles are equally expressed, leading to a phenotype that shows both traits distinctly.
2.Incomplete Dominance:
Neither allele is dominant, resulting in a blended phenotype.
3.Polygenic Inheritance:
Multiple genes influence a single trait, producing a range of phenotypes (e.g., skin color, height).
4.Epistasis:
The expression of one gene is affected by another gene, altering phenotypic outcomes.
5.Mitochondrial Inheritance:
Traits passed via maternal mitochondrial DNA.
6.Genomic Imprinting:
Gene expression varies depending on whether the gene is inherited from the mother or father, influenced by epigenetic modifications.