20 Of the following genetic phenomena, it is impossible to occur .

It is possible that a person with albinism marries a normal person, and the offspring is both a normal person and a person with albinism. AA+AA will produce AA.

The gene for intellectual disability in humans is recessive, and a normal couple can have children with intellectual disability.

That's right. AA+AA will produce AA.

The gene that determines the dimples of the human cheeks is the dominant gene, and a couple with dimples cannot have children without dimples.

Incorrect. AA+AA will produce AA.

The tall stems of peas are dominant traits, and the offspring produced by crossing tall peas with dwarf peas only show tall and not dwarf.

Incorrect. AA+AA will produce AA.

CD needs to see if there is a distinction between homozygotes and non-homozygotes, and it is impossible to tell. If you have to choose one, then choose C, because peas are generally homozygous in the wild, so D is likely.

A: Select C. Analysis:

A pair, the albinism patient is married to a normal person, and the offspring has both normal people, which may be albinism, such as: both parents are carriers of albinism genesaa aa aa pairs, the gene of human intellectual disability is recessive gene, a normal couple can also give birth to children with intellectual disability, and both parents may be carriers of intellectual disability genes. c False, the gene that determines the dimple of the human cheek is the dominant gene, and if a couple with dimples is a carrier of the dimple-free gene, their children may have children without dimples.

In the D pair, the tall stem of the pea is the dominant trait, and the tall pea is homozygous, and the offspring produced by its cross with the dwarf pea only show tall and do not show short stems, which is completely dominant.

The answer is: c.

A couple with dimples can have children without dimples if they are both heterozygous.

Item D is correct, the offspring produced by crossing tall peas with dwarf peas only show tall and not short, indicating that both parents are homozygous and that recessive traits are hidden in the next generation.

D false. D only says that peas are tall stems, not homozygous, and tall stems are dominant traits, so if they are crossed with dwarf peas, they may produce dwarf stems (in this case, tall stemmed peas are heterozygous).

Option C agrees with the statement upstairs.

Problem solving ideas: various traits of organisms are controlled by genes, and the inheritance of traits is essentially the transmission of genes from parents to offspring through the reproductive process, and in the process of sexual reproduction, * and egg cells are the "bridge" of gene transmission between parents and children

a. There are 23 pairs of chromosomes in each cell in the human body, including 22 pairs of autosomes and a pair of sex chromosomes, sex chromosomes include: X chromosome and Y chromosome, the sex chromosome composition of females is xx, and males are XY; Egg cells produced by females all contain an X chromosome; Half of the ** produced by males contains the X chromosome, while the other half contains the Y chromosome; When ** containing X chromosome combines with the egg cell to form a fertilized egg, it develops into a female, and when ** containing the Y chromosome combines with the egg cell to develop into a fertilized egg, it develops into a boy, so the birth of a male female is determined by the type of male ** so it does not fit the topic;

b. The somatic cells of each organism contain a certain number of chromosomes with different structures, these chromosomes exist in pairs, in the process of forming germ cells, the pairs of chromosomes are separated, one of each pair of chromosomes enters the ** or egg cell, and the fertilized egg formed by fertilization contains both the chromosomes of the egg cell and the chromosomes of **, so the number of chromosomes in the zygote is the same as that of the somatic cell; Therefore, there are 12 pairs of chromosomes in the somatic cell of rice Huiqing, and the number of chromosomes in the fertilized egg is 12 pairs after rice pollination and fertilization, so it does not meet the title.

c. Different manifestations of the same trait of the same kind of organism are called relative traits Long hair and short hair are hair growth phenomena and do not belong to traits, therefore, they do not belong to a pair of relative traits and therefore do not conform to the topic;

d. Genes determine the traits of organisms, and the genetic material has changed, for example, the parents are double eyelids AA and AA, and the genetic material of the child has changed to AA, and the traits have not changed, so it is in line with the topic

Therefore, D10 is chosen, and the following correct description of heredity is ( ).

a The birth of a male or female is entirely dependent on the male and has nothing to do with the female.

b There are 12 pairs of pre-dyeing chromosomes in the somatic cells of rice, and there are 12 chromosomes in the zygote.

c Long hair and short hair are a pair of relative traits.

d Even if the genetic material is changed, the traits of the organism are not necessarily inherited.

Which of the following statements about genetic factors is true? （）a.Genetic factors determine a person's brotherhood IQ.

b.Genetic factors determine the superiority and inferiority between races.

c.Genetic factors are only one part of the individual differences.

d.Genetic factors determine an individual's future destiny.

Correct answer c

<> from the genetics**, it can be seen that the genotypes of the offspring are aabb, aabb, The AABB phenotype is one, the AABB, AABB, and AABB phenotype is a kind of burnt, the AABB, AABB, and AABB phenotype is one, and the AABB phenotype is one Therefore, there are (4) phenotypes of two pairs of non-allelic heterozygous AABB self-inbreeding offspring under the condition of complete dominance

Therefore, d

Answer]: b, c, d, e

a, heredity does not directly determine the personality of a defeated body, but indirectly dives into the formation of the personality of the earth.

The answer is d. A heterozygous Aa is self-inbred to give birth to F1 individuals of 1 4AA, 1 2AA, 1 4AA, since AA individuals are not reproductive, so the F1 generation of individuals with reproductive ability are 1 3AA, 2 3AA;

If the F1 generation is self-bred, the offspring of 1 3AA are all prepared to be AA, and the individuals without reproductive ability in the offspring of AA are 2 3 times 1 4 equals 1 6, that is, if the F1 generation is inbred, the individuals without reproductive ability in F2 account for 1 6, and the individuals with reproductive ability account for 5 6.

If the F1 generation is free to mate, the individuals with reproductive ability are 1 3AA and 2 3AA produce A gametes as 2 3, and produce A gametes as 1 3, and the individuals without the reproductive ability of imitation socks in F2 account for 1 3 times 1 3 equals 1 9 of the total number of F2, then the individuals with reproductive ability are 8 9.