How do scientists count the number of genes?

Prokaryotes widely have several independent protein-coding sequences sharing a promoter or a group of promoters, so the prokaryotic genes, promoters and terminators, which are often used by several "genes" at the transcriptional level, are often not included in the boundaries of "genes". For convenience, in most cases we use only the boundaries of genes where the start and end points of protein translation—the start and stop codons—are extremely credible. Unlike eukaryotes, most of the "genes" encoding proteins have their own set of transcriptional regulatory elements (promoters, terminators).

Moreover, the untranslated region (UTR) of eukaryotes has more abundant regulatory elements. Therefore, when defining genes, it is not wrong to count the UTR region and the promoters and terminators involved in transcriptional regulation as well as genes.

But what is more troubling for eukaryotes is that the regulatory sequence region can be very long and more difficult, and there is no such clear boundary as the start codon and the stop codon. So actually, whether it's a prokaryotic or a eukaryotic organism, in most cases, we talk about "genes", which means "the part from the start codon to the stop codon". Sometimes, for example, in the gene annotation information we get, the gene also includes the part of the UTR on both sides, that is, the complete "transcription region", because there is enough transcriptome sequencing to help us determine this "boundary" that is not so easy to see.

It's not that we don't want the whole functional block from promoter to terminator to be included in the category of "genes", it's just that our understanding of DNA, the language of God, is too limited to understand such boundaries yet.

Phenotypic and genotypic algorithms, some of the general algorithms are illustrated below:

1) Genotype type: ABB and ABB are crossed, and the genotype types of its offspring are: 3 times 2 = 6 species.

2) Phenotypic type: AABB crossed with AABB, and its progeny phenotypic types were: 2 times 1 = 2 species.

Epigenotype, also known as hereditary type, reflects the genetic makeup of an organism, that is, the sum of all genes obtained from both parents. It is estimated that there are about 35,000,000 pairs of structural genes in humans.

Therefore, the genotype of the whole organism cannot be represented, and the specific gene used in genetics is often the genotype of a trait, such as the genotype of albinism is cc, which only indicates that this pair of alleles cannot produce coolinase. So the genotype is acquired from the parent and may develop into the genetic basis of a certain trait.

Phenotype refers to the sum of all traits in an organism. But the phenotype of the organism as a whole cannot be specifically represented. Therefore, the phenotype actually used often also refers to a specific trait in biological development.

For example, tyrosinase cannot be produced in the body. Phenotype is the manifestation of an organism that makes it possible for an inherited trait to develop into reality.

The relationship between genotype, performance, and environment The relationship between genotype, performance, and environment can be expressed by the following formula: phenotype = genotype + environment.

Taking human eugenics as an example, eugenics is the birth of individuals with excellent phenotypes in terms of intelligence and physique, and the advantages and disadvantages of phenotypes are determined by both genotype (genetics) and environment.

Of course, the relative importance of different traits in the development and performance of the two is different. People can apply the principle of this relationship to prevent and treat genetic diseases, such as phenylketonuria is an autosomal recessive genetic disease, which is determined by a pair of recessive pathogenic genes, and this environmental condition is that there is excess phenylalanine in the body.

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Problem description: Aa and Aa were crossed to obtain F1, F1 was self-crossed to obtain F2, and the phenotype was taken as dominant to mate freely, and the ratio of dominant recessive traits in the offspring was (A).

Analysis: The title "free mating" refers to free interbreeding Li Zhen, right?

The dominant genotypes in F2 are dd (1 copy) and dd (2 copies), and the probability of producing recessive coarse traits from their free crosses is calculated

1.As long as one party is dd, there is no recessive trait, only two dds can be generated, and the probability of producing two dds in this step is 2 3 * 2 3 4 9 (the probability of the first person obtaining dd is 2 3, and the probability of the second place obtaining dd is 2 3, which is multiplied by the principle of step-by-step counting and multiplication).

2.The probability of two DDs producing a recessive trait (equivalent to F1 self-breeding) is 1 4

Therefore, the probability of producing recessive traits in the whole process is 4 9*1 4 1 9 (multiplication principle), so the probability of dominant traits is 8 9, and the ratio is 8:1.

How genotype frequencies are calculated.

To calculate by proportion, it is necessary to look at the genes of the parents to calculate the approximate number of genotypes of the offspring.

Gene mutation rate * number of individual genes * number of individuals hail cluster = number of mutant genes.

So. Individual Gene = Number of Mutant Genes (Gene Mutation Rate * Number of Individuals) The number of genes mutated by an individual is the gene mutation rate * the number of individual genes.

Multiply by the number of individuals.

This is the total number of mutant genes in the branch.

From the source Sakura, the number of individual genes can be inferred backwards.

10 Mutations in 7 genes can have a mutation rate of its genes.

10 -5 count the total number of genes in these flies.

Divide the total number of genes by the total number of genes that each fruit fly has or disturb.

Random mating questions are calculated by gene frequency. Now all the deaths of RR are negligible, and RR and RR each account for 1 2Then the base 1 factor frequency of r is 1 2*1 2=1 4, and the gene frequency of r is 1-1 4=3 4 (or 1 2+1 2*1 2=3 4), then the offspring rr accounts for 3 4*3 4=9 16, rr accounts for 2*3 4*1 4=6 16 (multiplied by 2 because the male parent can produce r gametes and the female parent can produce r gametes, or vice versa), rr accounts for 1 4*1 4=1 16

The genotype ratio of F1 has been calculated and F2 is used in the same way. After the death of rr, rr accounts for 9 15 = 3 5, rr accounts for 2 5, and the gene frequency of r is 2 5 * 1 2 = 1 5So rr in f2 should account for 1 5 * 1 5 = 1 25