The process underlying differences in expression of a gene, according to which parent has transmitted, is called:
**Core Concept:** Genetic inheritance is the process by which an organism's genes are passed from parents to offspring. Genes are segments of DNA that determine an individual's traits and characteristics. In humans, a gene is made up of two alleles, one inherited from each parent. The expression of a gene depends on the dominance relationship between the two alleles. Dominance refers to the relative strength of the two alleles. Dominant alleles express their trait, while recessive alleles do not express their trait unless both alleles are recessive.
**Why the Correct Answer is Right:** Dominant inheritance is a type of genetic inheritance where one allele determines the expressed trait. In this case, the correct answer is C: **Co-dominance**. In co-dominance, both alleles for a gene are expressed, resulting in a combination of traits from both parents. This can lead to the expression of two different alleles, making it difficult to predict the expression based solely on the parent contributing the allele.
**Why Each Wrong Option is Incorrect:**
A. **Recessive Inheritance:** In recessive inheritance, only one allele determines the expressed trait. If both alleles are recessive, the trait is not expressed. This option is incorrect because it does not describe the co-dominant inheritance pattern.
B. **Semidominance:** Semidominant inheritance is when the expressed trait is intermediate between the two alleles. This option is incorrect because it does not accurately explain the co-dominant inheritance pattern.
D. **Symmetric Dominance:** Symmetric dominance is when the expressed trait is the same as the dominant allele. This option is incorrect because it does not describe the co-dominant inheritance pattern.
**Clinical Pearl:** Understanding genetic inheritance patterns is crucial for predicting the expression of traits in offspring and can help in diagnosing genetic disorders and counseling families about potential outcomes. Co-dominant inheritance is essential in explaining complex traits and is important for genetic counseling.