How many types of gene mutations are there? What are the types of genetic mutations?

A mutation from a dominant gene to a recessive gene is called a recessive mutation, and a mutation from a recessive gene to a dominant gene is called a dominant mutation. The vast majority are recessive mutations.

1) For sex cells:

If it is a dominant mutation, i.e., AA AA, it can be passed on to the offspring through the fertilization process and manifest itself immediately.

If it is a recessive mutation, i.e., AA AA, it does not manifest itself in the present generation and can only be manifested when the second-generation mutated gene is homozygous.

2) For somatic cells:

If there is a dominant mutation, the contemporary manifestation coexists with the original traits, forming a mosaic. The earlier the mutation, the greater the extent, and vice versa. Many of the "bud changes" on fruit trees are caused by somatic mutations, and once found, they can be propagated and preserved by cuttings, grafting or tissue culture.

If it is a recessive mutation, it does not manifest itself in contemporary times.

Genetic mutations cause the original gene to become its allele and is not directive: i.e., a gene can mutate in different directions; It can be a dominant mutation or a recessive mutation, but more often it is a recessive mutation.

There are several types of genetic mutations:

1. Nutritional deficiency type.

After the mutation, due to the lack of a certain enzyme, an additional nutrient needs to be added to grow the breeder, generally with "+" represents the use of a naturally existing component or an intermediate that can synthesize a certain component, and "—represents the strain that can not synthesize the component, such as his-, which represents the histidine-deficient type, and histidine needs to be added to the medium.

2. Resistance mutant.

Generally, S represents sensitivity to chemical drugs or antibiotics, and R represents resistance, such as STR8 represents that the strain is sensitive to streptomycin and cannot grow in the presence of streptomycin.

3. Conditionally lethal mutation.

With a lethal effect under one condition, the mutant strain cannot grow, but can still grow under another condition without a lethal effect, most commonly the temperature-sensitive mutant, which cannot grow in the temperature range where the parent can grow, especially at higher humidity (42), but at lower temperatures (25).

This strain is called TS strain, and its occurrence is due to the change of the peptide chain structure of some enzymes, which reduces the heat resistance of the enzyme, so it cannot survive at higher temperatures.

Characteristics of genetic mutations:

1. Less benefit and more harm.

Genetic mutations can have adverse effects, such as elimination or death, but in rare cases, species become more adaptable.

2. Non-directional.

For example, the A gene that controls black hair may be mutated to the A+ gene that controls white hair or the A- gene that controls green hair.

3. Beneficial.

Genetic mutations are generally harmful, but a very small number are beneficial mutations. For example, a bird has a short beak, and after a sudden mutation, the beak becomes longer, which makes it easier to catch food or water.

4. Independence.

A mutation in one allele of a gene locus does not affect the other allele, i.e., two genes in an allele will not be mutated at the same time.

5. Reproducibility.

The same mutation can occur multiple times between different individuals of the same organism.

6. Rarity.

At the time of the discovery of the first mutation gene, only one was found instead of several white compound eye fruit ropes, indicating that the mutation is extremely rare, that is, the mutation of the wild-type gene is very low (see table for some representative gene mutation rates).

The above content referenceEncyclopedia - Resistance mutant.

The above content referenceEncyclopedia—auxotrophic type.

The above content referenceEncyclopedia—Conditionally lethal mutations.

The above content referenceEncyclopedia—Gene mutations.

1. Static mutations.

Static mutation is a gene mutation that always occurs at a certain frequency in each generation of an organism, and can be relatively stable with the reproduction and alternation of generations.

a) Point mutations: changes in a single base or base pair in a DNA polynucleotide strand.

1. Base substitution: a mutant form in which a specific base or base pair in the polynucleotide chain of a DNA molecule is replaced or replaced by other bases or base pairs.

2. Frameshift mutation: due to the insertion or deletion of base pairs in the genomic DNA polynucleotide chain, some or all of the triplet genetic codon combinations have been changed since the insertion or deletion point.

2) Deletion, insertion, and rearrangement of small fragments.

1. Microdeletion: caused by a small fragment not being copied normally or failing to be repaired during the repair process of DNA replication or damage.

2. Micro-insertion: During the process of DNA replication or damage, a small fragment is inserted into the DNA strand, and the result is a micro-insertion of the corresponding small fragment in the new strand.

3. Rearrangement: When there are more than two breaks in the DNA molecule, the two ends of the small fragments formed are reversed and reconnected, or different fragments change the original structural order and reconnect.

2. Dynamic mutations.

The abnormal changes or diseases of some monogenic inherited traits are caused by the amplification of some short tandem repeats in the DNA molecule, especially the trinucleotide tandem repeats of the gene coding sequence or flanking sequence, because the number of tandem trinucleotide repeats can show an increasing cumulative mutation effect with the transmission of generations, so it is called dynamic mutation.

In biology, a mutation is a change in the nucleotide sequence in the genome of an organism, virus, or extrachromosomal DNA. Genetic mutations include point mutations caused by a single base change, or deletions, duplications, and insertions of multiple bases.