Question

Patterns of inheritance are usually more complicated than what is predicted by Mendelian genetics. Explain four possible exceptions to Mendelian genetics involving the inheritance patterns of a single gene and provide an example of each.

Answer 1

Exceptions to Mendelian genetics include incomplete dominance, codominance, multiple alleles, and environmental effects, all contributing to more complex inheritance patterns, departing from simple dominant-recessive allele interactions.

Step-by-step explanation:

Patterns of inheritance are often more complex than Mendel's simple dominant and recessive alleles models. Here are four possible exceptions to Mendelian genetics involving the inheritance patterns of a single gene:

1. Incomplete dominance is where the phenotype of heterozygotes is intermediate between the phenotypes of individuals homozygous for either allele. An example is the snapdragon flower, where crossing red (RR) and white (rr) flowers results in pink (Rr) offspring.
2. Codominance occurs when both alleles in a heterozygote are fully expressed, with neither being dominant over the other. An example of codominance is the human blood type AB, where both A and B alleles are expressed.
3. Presence of multiple alleles in the gene pool provides more than two possible alleles for a trait. For instance, the human blood type gene has three alleles: A, B, and O.
4. Environmental effects can also influence the expression of certain genes, making the trait's inheritance appear to deviate from Mendelian patterns. An example is the Himalayan rabbit, where colder temperatures cause dark fur to express on the extremities.

Answer 2

Please find the explanation of the four possible exceptions to Mendelian genetics below.

Step-by-step explanation:

Genetics, generally, has to do with how genes are inherited or transferred from parents to offsprings. Gregor Mendel, however, explained this concept in his principles of inheritance called Mendelian genetics. There are, however, exceptions to this mendelian principle called Non-mendelian pattern of inheritance i.e patterns of inheritance that do not follow Mendel's principles. Four of them are explained below:

- Incomplete dominance- This non-mendelian inheritance pattern occurs when one allele of a gene does not completely mask its allelic pair, but instead forms an intermediate phenotype. This is in contrast with Mendelian genetics that proposes complete dominance. For example, a red and white flower produce a pink flower (intermediate).

- Codominance- This is another non-mendelian inheritance where two alleles of a gene are simultaneously expressed. For example, roan cattles is a combination of both red and white hairs.

- Multiple alleles: Some traits in a population are controlled by more than two alleles, as explained in mendelian inheritance. Examples of trait controlled by multiple alleles is height in humans.

- Sex-linked inheritance: Some traits are controlled by genes on sex chromosomes i.e. X and Y chromosomes. This genes exhibit inheritance pattern that are different from Mendel's. Example is haemophilia disease controlled by an affected gene on the X-chromosome.