The laws of biological heredity, what are the laws of heredity

The entry point of nail disease is -5 disease, -6 is diseased, and the birth of -3 is diseaseless, indicating that nail disease is autosomal dominant inheritance.

Why isn't it X-chromosome dominant? Because if it is X chromosome dominant inheritance, then the genotype of -5 is XBY, because his daughter wants to get an XB from him, so the offspring daughters are all patients, and -3 in this figure is disease-free, indicating that it is not X chromosome dominant inheritance;

If -1 does not carry the pathogenic gene of disease B, then disease B is inherited with x, because -1 and -2 are not diseased, and -2 is diseased, indicating that disease B is transmitted from the X chromosome of -2 to -2;

If there is no sentence "-1 does not carry the disease-causing gene of disease B", then disease B may be autosomal recessive or X chromosome recessive.

Rule: Something out of nothing - hidden.

There is no middle generation - explicit.

The father and daughter are sick, and the mother and child are sick - often hidden.

Father's illness and daughter's illness, mother's child's illness - often obvious.

This question: first determine whether it is inherited with sex, and see if 1 gave birth to a daughter and son without disease, so nail disease is not inherited with sex.

Looking at 1 2 without disease B, but giving birth to 2 with disease B, plus the people suffering from disease B are all males, it can be judged that disease B is accompanied by x recessive inheritance

Looking at nail disease from to in line with the father's and daughter's disease, and the mother's disease and the child's disease, [nail disease is autosomal recessive inheritance].

Of course, the above rules can help you make the problem quickly, but if you can't remember, or are afraid of messing up, then use the hypothetical method.

The hypothetical method is that you first look at what you think the disease looks like and write it directly, and then push it step by step, and then change it if it is not right.

Judging the disease of A: First of all, the No. 5 and No. 6 of the second generation, both of them are sick, but they give birth to children who are not sick, according to the formula: there is no manifestation in the middle of life; Dominant inheritance is seen in male diseases, and mothers and females are disease-free and non-concomitant.

So I found a male patient with the second generation No. 5 and observed that his daughter was not sick, so it was finally determined that nail disease was autosomal inheritance. Therefore, nail disease is common.

Judgment of disease B: No. 1 and No. 2 of the second generation do not have disease B, while their son No. 2 of the third generation has disease B, which is in line with the mantra of creating something out of nothing. Recessive inheritance is resistant to female disease, and the father and son are disease-free and non-partnered.

If the stem tells the second generation of the No. 1 B-free gene, it can be judged that the disease can only be inherited by the mother. That is, the No. 2 of the third generation, there is only one diseased gene, so the man's B disease gene is: xby, so it is inherited with x recessive.

Hope it can help you, satisfied.

Creating something out of nothing is recessive, recessive genes are seen as female diseases, and female diseases are accompanied by both father and son.

I don't know how to ask questions.

The laws of heredity mainly include: the law of gene segregation, the law of free combination of genes, and the law of linkage and exchange of genes.

1. The law of gene segregation.

Relative traits: Different types of expression of the same trait in the same organism are called relative traits.

Dominant traits: In genetics, the parental trait that appears in hybrid F1 is called a dominant trait.

Recessive traits: In genetics, the parental trait that is not shown in hybrid F1 is called a recessive trait.

Trait segregation: The phenomenon of both dominant traits and recessive traits (such as tall stems and short stems) appearing in hybrid offspring is called trait segregation.

Dominant genes: Genes that control dominant traits are called dominant genes. It is generally represented by capital letters, and the pea tall stem gene is represented by d.

Recessive genes: Genes that control recessive traits are called recessive genes. It is generally represented by lowercase letters, and the pea dwarf stem gene is represented by d.

2. The law of free combination of genes.

The law of free combination of genes: when F1 produces gametes, the non-allelic genes on non-homologous chromosomes show free combination at the same time as the allele is separated, which is called the free combination law of genes.

3. The law of linkage and exchange of genes.

Two traits of the same parent often tend to be inherited together in F2, rather than a 3:1 rule, and this phenomenon is called linkage inheritance.

The linkage and commutation law says that genes located on the same chromosome are linked to each other and are often passed together (linkage law), but sometimes segregation and recombination occur because pairs of alleles on the homologous chromosome are exchanged.

The law of heredity is Mendel's lawIn 1865, the Austrian imperial geneticist Grigor Mendel published and gave birth to the famous law of genetics. He revealed two fundamental laws of genetics, the law of separation and the law of free combination, collectively known as Mendelian laws of inheritance.

An important application of Mendelian genetic law in practice is in the cross-breeding of plants. In the practice of cross-breeding, the excellent traits of two or more varieties can be purposefully combined, and then through self-crossing, continuous purification and selection can be carried out to obtain a new variety that meets the ideal requirements.

Mendelian Theory of Laws of Inheritance and Its Application Value.

Theoretically, the law of free combination provides an important theoretical basis for explaining the diversity of organisms in nature. Although there are many reasons for the variation of organisms, the free combination of genes is an important reason for the diversity of biological traits. For example, if a pair of organisms with 20 pairs of alleles (each of which is on 20 pairs of homologous chromosomes) is crossed, there may be 2 20 = 1048576 phenotypes of F2.

This may explain why there is so much diversity in the world.

The three laws of heredity are as follows:

1. The First Law: Also known as the Law of Separation or the Law of Equivalent Separation. This law states that when an individual reproduces, the genes inherited from their parents are separated and passed on to the next generation in an equal probability manner.

Mendel's experimental observations of pea plants showed that genes were segregated and passed on to offspring in two equal amounts.

2. The second law: also known as the law of free combination or the law of independence. This law states that genes are inherited in a freely combined manner during the reproductive process of an individual, without affecting each other.

That is, genes with different traits can be freely combined during the formation of gametes without being affected by other genes. This law reveals the independence between genes.

3. The Third Law: Also known as the Law of Pairing or the Law of Pairing Separation. This law states that two genes, which are present on the same pair of chromosomes, can be separated during an individual's reproduction and independently enter different gametes.

This means that the inheritance of the leakage causes of the Quishen faction is not absolutely linked, but can be recombined by means of re-widening and rematching.

Characteristics of the three laws of heredity

1. Conciseness: The three laws of heredity provide a concise and clear description, so that the basic principles of genetics can be accurately explained and disseminated. Mendel summarized these laws from experimental observations of pea plants, and reduced complex genetic phenomena to simple laws.

2. Universality: The three laws of heredity apply to many organisms, not only in the field of plants, but also in animals and microorganisms. These laws have a wide applicability, revealing universal laws of gene transmission and genetic variation.

3. Experimental basis: The three laws of heredity are based on Mendel's well-designed pea plant experiments. Mendel came up with these laws through extensive observation and experimentation, collecting data and conducting statistical analysis.

4. Revolutionary: The proposal of the three laws of heredity has had a revolutionary impact on genetics. They broke the traditional concept of genetic transmission at that time, revealed the discrete and enviable purity of genes, and provided the foundation for later genetic research.