How to judge the explicit recessiveness, don t you need to determine whether it is a purebred before

High school biology topics are covered in all aspects. First of all, safflower and white flowers cannot be heterozygous, there must be one recessive homozygous, no matter who is recessive, there must be an AA, so the offspring genes are A, and A, and the offspring of white flowers and safflower are all red, indicating that they are A, red is dominant, and the maternal safflower is AA

No, its premise is that the offspring are all safflowers, then the offspring must be a combination of AA, because the parents are safflower and white flowers, this question does not let you speculate about what color the offspring of safflower and white flowers are, but has determined that the offspring is safflower, and the reverse past reasoning is it.

How to tell if a trait is dominant or recessive.

The dominant genes and recessive genes, dominant traits and recessive traits of organisms are the contents of the annual high school entrance examination. In the genetics test center, there is often a type of question that requires students to understand the meaning of the question and determine whether a trait of an organism is a dominant trait or a recessive trait. In 2009, many provinces and cities appeared in the high school examination questions.

Selected and summarized as follows:

Example 1(2009) The yellow and blue of parrot feathers are a pair of relative traits, if h is used to indicate the gene that controls the dominant trait, and h represents the gene that controls the recessive trait, please answer the following questions according to the table:

Based on the genetic results shown in the table, it can theoretically be inferred that the relative traits of parrot feather color are recessive traits.

Analysis: From the question, it can be seen that the traits of the parents are yellow, and their offspring have both yellow and blue. Assuming that yellow is a recessive trait, the genome of the parent becomes HH and HH, and the genome of the offspring is HH, both of which exhibit yellow.

This is different from the genetic results in the question. So the assumption is wrong, that yellow is the dominant trait.

Answer: Blue.

Non-sweet dominant, by the analogy of Mendelian experiments: pure tall stems and dwarf hybrids with full-height stems, !In this question, non-sweet and sweet are pollinated and hybridized with each other, and there is no sweetness on non-sweet: non-sweet is dominant.

1. Definition distinction:

Dominant traits: Homozygous parents with a pair of relative traits are crossed, and the offspring are heterozygous, and one of the corresponding alleles has a significant effect on the trait exhibited, while the other does not exhibit it temporarily. The trait of the parent that is exhibited is the dominant trait.

Recessive trait: When two homozygous parents with opposite traits are crossed, a parental trait that does not appear in the offspring.

2. Judgment method:

1) Definitional approach.

When a pair of relative traits are crossed by purebred parents, the traits exhibited by the offspring generation are called dominant traits, and the other traits that are hidden and not yet appear are called recessive traits. When applying the definition method to judge, it is necessary to meet the condition that the parents of a pair of relative traits are purebred.

2) Trait separation method:

The individual self-inbreeding of a certain trait, or the crossbreeding of a pair of parents with the same trait, the second generation of the child not only appears the same trait as the parent, but also appears a new trait different from the parent, this phenomenon is called trait separation, the same trait as the parent is the dominant trait, and the new trait is the recessive trait. and dominant traits: recessive traits = 3:

1。(3) Trait segregation ratio method.

According to the law of gene segregation, in the phenomenon of trait segregation, the segregation ratio of dominant and recessive traits of offspring should be 3 1, so in the segregation ratio of traits of progeny 3 1, the traits accounting for 3 4 are dominant traits and the traits accounting for 1 4 are recessive traits.

4) Hypothetical method.

Assumptions can be made when the judgment cannot be made based on the above methods.

That is, assuming (hypothesis 1) that the traits of a certain parent are dominant (recessive), it is estimated according to the hypothetical conditions, and if it is inconsistent with the facts, hypothesis 1 is not valid, and the explicit recessiveness of the parent can be judged;

If it is consistent with the facts, it should be assumed (hypothesis 2) that the traits of the other parent are dominant (recessive), and whether it is consistent with the facts should be inferred according to the conditions of the hypothesis, and if it is inconsistent with the facts, it means that the original hypothesis (i.e., hypothesis 1) is true.

How to tell if a trait is dominant or recessive.

To put it simply, when two homozygous alleles expressing different traits are crossed, the traits that are manifested by the hybrids and the offspring are dominant traits, and those that cannot be exhibited are recessive traits.

To illustrate with an example:

Purple and green traits, a hybridization test was carried out to determine who is the dominant gene purple * violet = purple, green violet dominant, green recessive.

Purple * Green = All Purple Violet Dominant, Green Recessive.

Only these two cases can determine which one is dominant.

Explanation: First: heterozygous trait separation, the offspring show traits that the parents did not express, this trait (green) must be recessive.

Second, the parents are all homozygous, and the offspring are all heterozygous, (that is, the hybridization experiment of Mendel's law of segregation), and the kind of parental trait (green) that heterozygotes do not exhibit must be recessive.

Identifying organisms as pure-breeded organisms can be used for plants, and self-crossing and cross-testing methods can be used, among which self-crossing is the easiest method; The method of measurement is generally used. In order to distinguish the dominant and recessive relationship of a pair of relative traits, organisms can be allowed to cross, and there are two situations that can be judged: if there is another new relative trait in the hybrid offspring of two biological individuals with the same trait, the trait of the parent is a dominant trait; If an organism with different traits is crossed and only one trait appears in the offspring, this trait is a dominant trait. Constant self-inbreeding can significantly increase the homozygosity of biological varieties.

The significance of cross-testing is that it allows for the identification of the genotype of dominant individuals.

One way is to hypothesize, which is either dominant or recessive, and is judged according to the dominant male and female pretty. The second way is to look at the intergenerational transmission as explicit and the intergenerational transmission as implicit.

Generally speaking, dominant inherited diseases have the characteristics of continuous inheritance from generation to generation, while recessive inheritance has the characteristics of intergenerational inheritance, and after preliminary judgment, we will see whether there is a difference in the number of affected individuals between males and females. Conversely, if there are more affected individuals in women than in men, it may be accompanied by X-manifestation, such as anti-VD rickets; If the disease is equal in both men and women, it may be autosomal inheritance.

But this is not absolute, it needs to be assumed first, and then verified, that is, it is assumed to be a dominant or recessive disease according to the genetic characteristics between generations, and then verified with the second half of the formula, or directly write the genotype to see if it can be written.

Note that when the inheritance is in line with the x-dominant inheritance, it must be in line with the usual manifestation; In the same way, when the inheritance is in line with the companion x stealth inheritance, it must be in line with the common recess, so it is necessary to first test whether it is in line with the companion inheritance.

This is what you think wrong. Individuals of Aa, A and A are both expressed, except that A masks the effect of A, so that the phenotype shows the effect of A.

Pick A is not wrong. It's not that the gene is not not expressed, such as the red eyes and white eyes of the fly, the white eye gene of the heterozygous is also expressed, but only red can be seen after the two colors are mixed, I remember a high school biology book about a variegated horse, which can illustrate this situation.

Traits of recessive genes are manifested.

It's just that it's obscured by the trait expressed by the dominant gene (the trait is obvious).

This question is a test of text comprehension, and it is not good, if our teacher must have crossed this question, I also think that A and D have the same meaning.

The landlord can't just memorize this question.

The answer is A, not that the recessive gene is not expressed, but that the expressed recessive trait is covered by the dominant trait, that is, the trait expressed by A is covered by the trait expressed by A, for example, you wear a white dress inside, and then a white dress outside, that is, AA, it still looks white, but if you wear white inside and red outside, it looks like red on the outside, that is, AA, red covers up the white, not that you don't wear white.

n is isolated in circles, and the eigenrival values of a are all real numbers.

The rank bai of the matrix has nothing to do with the number of eigenvalues of the matrix.

zhin order matrix dao

In the range of complex numbers, there must be n eigenvalues (the number of eigenvalues is calculated as a multiplicity), and in this sense, the number of eigenvalues of the matrix is related to the order of the matrix. It is not certain how many eigenvalues there are in the range of real numbers for n-order matrices.

The nth-order real symmetry matrix must have n real eigenvalues (the number of re-eigenvalues is calculated by the number of multiplicities).

Hehe, send sub-questions. The eigenpolynomial obtained by the nth order square matrix must be a unary n-order equation and must have n roots (including double roots, but the total number must be n).

The landlord should be too principled, the teacher said, n each Gaier circle is isolated, and the eigenvalues of a are real numbers.