BIOLOGY Volume 3 - A Guide to General Biology - 2004

24. VARIATION AND GENETICS

24.1. Mendel's Studies

24.1.4. Summary of Mendel's Hypothesis

The statements formulated below use terminology accepted in modern genetics.

1. Each trait of a given Organism is controlled by a pair of alleles.

2. If an organism carries two different alleles for a given trait, one of them (the dominant one) may be expressed, completely masking the expression of the other (recessive) trait.

3. During Meiosis, each pair of alleles separates (segregates), and each gamete receives one allele from each pair (law of segregation).

4. During The formation of male and female Gametes, any allele from one pair may end up in a gamete together with any allele from another pair (law of independent assortment).

5. Each allele is transmitted from generation to generation as a discrete, unchanging unit.

6. Each organism inherits one allele (for each trait) from each of its parents.

NB. The inheritance mechanism described here for dihybrid crosses, the given Examples, and the typical 9:3:3:1 ratio apply only to traits controlled by genes located on different Chromosomes. If the genes are located on the same chromosome, independent assortment of this type is not always observed (see Section 24.3).



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