Recessive traits are traits that cannot be exhibited by organisms, what is wrong?

The recessive trait is relative to the dominant trait, but both alleles are dominant genes or one is dominant when it is the dominant trait, but when both genes are recessive genes, it is a recessive trait, as long as you have studied high school sophomore organisms, you will know.

A dominant trait, abbreviated as dominant, is defined as a parental trait that appears in a child generation when two homozygous parents with relative traits are crossed. Mendel called the parental trait manifested in F1 the dominant trait. In Mendel's hybrid experiments, whether white flowers were used as the paternal parent and safflower as the female parent, or safflower as the male parent and white flowers as the female parent, all the plants of the offspring generation had red flowers, and there were no white flowers or other colored flowers.

Safflower is a dominant trait relative to white flowers, as safflower manifests itself in the offspring. Although white flowers are not dominant, there is no doubt that they can manifest themselves.

The heterozygous inbred generation exhibits dominant traits, and those that do not exhibit are called recessive traits.

Recessive traits cannot be manifested in heterozygous but can in homozygous.

It is the absence of manifestation, obscured by dominant traits, not the inability to be.

Recessive traits and dominant traits are for relative traits, the so-called recessive traits are traits that are not manifested when the genes that control both traits are present, and dominant traits are what you see and manifest.

For example, the tall stem pea and the short stem pea in Mendelian experiments are often mentioned in textbooks, and the heterozygous shows tall stems, so we say that tall stems are dominant traits. Dwarf stems are traits that do not manifest themselves, so they are recessive traits.

Dominance is relative, a trait controlled by a single gene, a gene locus has two alleles, mainly depending on which trait is expressed in the heterozygous state of the two alleles. What is manifested is the dominant trait, and what is not manifested is the recessive trait.

If two parents with relative traits are crossed, and the offspring have only one phenotype, the child represents the dominant trait and the hidden trait is recessive.

The homozygous hybrid generation exhibits dominant traits, and those that do not exhibit recessive traits.

Organisms9 are controlled by a pair of genes9 when a pair of genes control a trait in the cellular9 and when a pair of genes are dominant, one is dominant and the other is recessive, the organism exhibits dominant gene control 9 traits; When the 9 genes that control a certain trait are all recessive, the recessive gene controls the 9 traits to manifest Therefore, the 9 traits exhibited by organisms are not necessarily dominant traits, and recessive traits can also be manifested such as single eyelids, so the statement stem 9 is wrong

So the answer is:

a. When the genes that control a trait are recessive, the organism exhibits a recessive trait A error b. When the genome is a dominant gene or one is a dominant gene and one is a recessive gene, the organism exhibits a dominant trait; Recessive traits manifest themselves only when the genes that control a trait are recessive, so the frequency of occurrence of dominant traits is higher than that of recessive traits

c. Different manifestations of the same trait of the same species are called relative traits; The tall stem of pea and the lack of lodging resistance are two traits that cannot be called relative traits c error

d. As long as the genome is recessive, it will show recessive traits d error Therefore, b

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 feather color 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 be theoretically 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 the 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.

Example 2 (2009 Jinzhou) A class of students conducted a sampling survey on the genetic status of double eyelids and single eyelids in the population, and obtained the following data:

The group of mating methods was investigated.

Number of children in the family.

Single eyelid Double eyelid.

Single eyelid Single eyelid 48 58 0

Double eyelids Double eyelids 85 24 70

Double eyelid Single eyelid 162 54 126

Analysis: From the condition of this question, it can be seen that there are three groups of parents, two of which have the same traits, and the parents of the group are all single eyelids, and the children born are all single eyelids, and we cannot determine that the dominant trait is single eyelids from this set of data. Because regardless of whether the single eyelid is dominant or recessive, the parents of the single eyelid are likely to give birth to children who are all single eyelids.

The parents of the group all had double eyelids, and the female children had double eyelids and some had single eyelids. Similar to the situation in the previous question. Therefore, we can determine that the dominant trait of the eyelid is double eyelid and the recessive trait is single eyelid.

Concepts of dominant and recessive traits:

A dominant trait refers to a trait that manifests itself as an individual's explicit trait in genetics, i.e., phenotype.

Recessive traits refer to traits that are not manifested in genetics as individual penetrant, i.e., genotypes. Homozygous parents with a pair of relative traits are crossed, and the offspring are heterozygous, with one of the corresponding alleles having a significant effect on the trait exhibited, and the other not exhibiting for the time being. The trait of the parent that is exhibited is the dominant trait.

Recessive traits are parental traits that are not expressed in the offspring produced by the crossing of parents with relative traits.

In genetics, each individual has a set of genes that determine the traits of an individual. The gene is made up of two alleles, one from the mother and one from the father. If the two alleles are identical, they are called homozygous; If the two alleles are different, they are called heterozygous.

A dominant trait is a trait that requires only one allele to be expressed, while a recessive trait requires two identical alleles to be able to manifest.

The inheritance of dominant traits and recessive traits is different. The inheritance law of dominant traits is Mendelian inheritance, that is, with the separation of alleles and random combination of traces, the phenotypes of offspring will show a certain proportional relationship. The inheritance law of recessive traits is the recessive inheritance law, that is, recessive alleles can only manifest themselves when two identical alleles are combined.

In genetics, there is also a trait that is not completely dominant. Incomplete dominance is when two different alleles are combined to exhibit a trait that is somewhere in between. For example, the degree of curly hair in the human Zhenzhou Bridge is an incomplete trait.

If a person has an allele for curly hair and an allele for straight hair, then his hair will be somewhere between curly and straight hair.