Explain the mechanisms by which genes transmit information. A genotype is the underlying combination of genetic material present in an organism but invisible; a phenotype is the visible trait, the expression of the genotype. For example, \(\mathrm{PKU},\) a disease that causes brain damage and intellectual disabilities, is produced by a single pair of genes inherited from one's mother and father. If neither parent carries a gene for the disease, a child cannot develop PKU. Even if one parent carries the recessive gene, but the other doesn't, the child cannot inherit the disease. However, if both parents carry the recessive gene, there is a one in four chance that the child will have PKU.

Step by step solution

01

- Genotype and Phenotype Understanding

Genotype refers to the genetic composition of an organism. It is a record of an organism's genetic information inherited from its parents. This genetic inheritance influences but does not determine the organism's physical appearance. Phenotype, on the other hand, is the physical manifestation or the expression of the genotype. It comprises the organism's observable characteristics such as height, skin color, hair type etc. Both, together, play a key role in gene transmission.

02

- Disease Inheritance

Genes also play a crucial role in the inheritance of many diseases. Some diseases are hereditary and can be passed down from generation to generation, based on individuals' genotypes. For example, PKU is a disease that is caused by inheriting a specific pair of genes from both parents. If neither one of the parents has the disease-causing gene, the child won't have the disease.

03

- Importance of Recessive Genes

PKU is a disease that is passed down through recessive genes. This means that both parents must carry the gene for the disease to be passed on to their child. If one parent does not carry the gene, the child won't inherit the disease. If both parents do carry the recessive gene, there's a one in four chance that their child will inherit the disease. This shows that inheritance is not only about passing on genes but also about the nature of those genes - whether they're dominant or recessive.

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