What is the difference between the modern concept and the traditional concept of genetic diseases?

The concept of classical genetics genes: genes have the following * * * characteristics: (1) genes have the important characteristics of chromosomes (that is, genes are located on chromosomes), can replicate themselves, are relatively stable, and are regularly distributed during private division and meiosis; (2) The gene occupies a certain position (i.e. locus) on the chromosome, which is the smallest exchange unit, that is, the unit that cannot be divided during recombination: (3) The whole gene is mutated, so it is a mutant unit; (4) A gene is a functional unit that controls one or several characters of a developing organism, such as white flowers and safflower.

In short, classical genetics holds that a gene is the smallest unit and inseparable. It is both a structural unit and a functional unit.

The concept of gene in molecular genetics: the development of molecular genetics reveals the secret of genetic code, which makes the concept of gene implemented in concrete substances, that is, a gene is on a DNA molecule, and a gene is equivalent to a fragment of a DNA molecule, carrying specific genetic information. This genetic information can be transcribed into RNA, including messenger RNA, transfer RNA and ribosomal RNA; Or messenger RNA is translated into polypeptide chains.

On the other hand, in the fine microbial genetic analysis, it is found that genes are not the smallest inseparable units, but much more complicated genetic and variation units.

With the development of modern genetics, at the molecular level, genes are divided into three units according to recombination, mutation and function:

(1) Mutant: refers to the smallest unit of mutation when a character is mutated. Mutants can be as small as only one base pair;

(2) Reassembler: refers to the smallest unit that can be exchanged when a character is recombined. A commutator can only contain one base pair;

(3) cis-trans refers to a functional unit, which basically conforms to the size of a gene or is slightly smaller. It consists of a piece of synthetic DNA corresponding to polypeptide chain, with an average of 500- 1500 base pairs.

As the structural unit of genes, classical genetics actually contains a large number of mutants or recombinants. It is no longer true that genes are the smallest structural units, but the concept that genes are functional units is still correct. The concept of gene is that (1) can transcribe a complete RNA molecule or encode a polypeptide chain. (2) Determine the function through the cis-trans test or complementary test. In other words, a gene is equivalent to a cis-trans, including many mutants and recombinants.