What is a gene mutation?

Gene mutation refers to the sudden variation of genome molecules, which may be inherited or caused by a disease. This type of gene mutation has the characteristics of universality, rarity, reversibility, more harm than good, and uncertainty. At present, the medical community does not have a particularly effective method to treat this disease, and most patients need to rely on their own recovery to achieve the treatment goal.

1. What is a gene mutation?

Gene mutation refers to the sudden and heritable variation of genomic DNA molecules. From a molecular level, gene mutation refers to a change in the base pair composition or arrangement order of a gene structure. Although genes are very stable and can accurately replicate themselves when cells divide, this stability is relative. Under certain conditions, genes can suddenly change from their original form to another new form. That is, a new gene suddenly appears at a site and replaces the original gene. This gene is called a mutant gene. As a result, new traits that their ancestors never had suddenly appear in their offspring.

2. Characteristics of Gene Mutations

1. Universality

Gene mutations are common in all species in nature.

2. Rarity

When the first mutant gene was discovered, not several white compound eye fruit ropes were found but only one, which shows that the mutation is extremely rare, that is, the wild-type gene mutates at an extremely low mutation rate (see the table for some representative gene mutation rates). In organisms that reproduce sexually, the mutation rate is expressed as the probability of each gamete undergoing a mutation, that is, the number of mutant gametes in a certain number of gametes. In asexual bacteria, the mutation rate is expressed as the probability of each bacterium mutating in each cell generation, that is, the number of times a certain number of bacteria mutate during one division. It is estimated that in higher organisms, only 1 out of approximately 10^5~10^8 germ cells will undergo a gene mutation. Although the frequency of gene mutation is very low, when there are many individuals in a population, it is possible for a variety of random mutations to arise, sufficient to provide rich heritable variation.

3. Reversibility

The process by which a wild-type gene mutates into a mutant gene is called forward mutation. The rarity of positive mutations indicates that the wild-type gene is a relatively stable structure. A mutant gene can then become a wild-type gene through mutation, a process called back mutation. It can also be seen from the table that back mutation rarely occurs, which shows that the mutant gene also has a relatively stable structure. However, the forward mutation rate is always higher than the reverse mutation rate. This is because structural changes at many positions within a wild-type gene can lead to gene mutation, but only a structural change at one position within a mutant gene can restore it to its original state.

4. Less benefit but more harm

Generally, gene mutations will have adverse effects, leading to elimination or death, but in very rare cases, they will enhance the adaptability of species.

5. Non-directional

For example, the A gene that controls black hair may mutate into the a+ gene that controls white hair or the a- gene that controls green hair.