Why mutated genes don t necessarily produce phenotypic effects

Codons are degeneracious, the same amino acid may correspond to multiple codons, and the mutated gene happens to be the same codon that translates the amino acid (synonymous mutation).

The codon is wobble, and the third codon is not translated strictly according to the base complementary pairing.

The location of the mutation is on the exon, or it is not expressed at all without translation.

Even if there is a missense mutation and the translated amino acids are changed, the amino acids located on the surface of the protein generally do not affect the function and activity of the protein.

The organism itself has a repair function (photoresurrection, excision repair, recombination repair, emergency repair).

According to phenotypic effects, mutants can be divided into morphological mutants, biochemical mutants, and lethal mutants. Such a distinction does not address the nature of mutations, and it is not strict. Because morphological mutations and lethal mutations necessarily have their biochemistry.

basis, so strictly speaking, all mutants are biochemical mutants.

1.morphological mutations: sickle cell anemia in molecular structure; Red eyes mutate to white eyes at the individual level.

2.Biochemical mutation: hemoglobin in sickle cell anemia.

The principle of structural mutation.

3.Lethal mutations: such as recessive homozygous lethality.

Auxotrophic type: such as high serine dehydrogenase-deficient strains, which cannot grow on a medium that does not contain methionine threonine, but can synthesize lysine in large quantities, and is often used in the production of lysine in industry.

Resistance mutations.

Conditional lethal mutations.

Morphological mutant: used to screen strains.

Additions are welcome.

Morphological mutations, biochemical mutations, lethal mutations, conditional lethal mutations.

Types: point mutations, deletions, insertions, inversions, and dynamic mutations.

Genetic effects: base displacement mutations (synonymous mutations, missense mutations, nonsense mutations, stop codon mutations or elongation mutations), frameshift mutations, fusion mutations, etc.

After genetic mutations, some organisms exhibit variant traits, while others do not.

The main reasons are: (1) mutation, the site of the abortion may be in the non-coding site.

2) The codon formed after the gene mutation and the protocodon determine the same amino acid.

3) Genetic mutations are recessive mutations, such as AA becoming AA, which will not lead to a change in traits.

In high school, you can choose the second reason.

Genetic mutations can only change the genotype, but there are many factors that contribute to whether or not it is reflected in the trait

For example, a mutation in a AA is A, and the genotype is AA, but it still reflects the dominant trait, which is the same as before the mutation; In addition, the principle that "phenotype is the result of a combination of genotype and environment" does not support the claim that genetic mutations must be able to change the phenotype of organisms.

Therefore, the statement that "genetic mutations must be able to change the phenotype of organisms" is false.

Firstly, gene mutations are divided into nonsense mutations and sense mutations, and some gene mutations will occur in the non-coding region and do not affect gene expression, which becomes nonsense mutations. In addition, an amino acid does not only have one codon corresponding to it, sometimes, although the gene mutation changes the codon, but the encoded amino acid does not change, so the protein structure does not change, and then the phenotype does not change, which is another form of nonsense mutation.

Second, phenotype is determined by both genotype and environment, and a change in genotype does not necessarily change the phenotype of an organism.

First of all, genetic mutation does not necessarily change the phenotype of organisms, because phenotype is determined by two factors, genotype and environment, genotype change, does not mean that phenotype must change; Secondly, the gene mutation is not necessarily dominant, it may be from AA mutation to AA, and the phenotype is still unchanged.