The basic laws of biological heredity and the question of companion inheritance 100

Answer]: Companion inheritance refers to the fact that the basal strooping that controls the trait is located on the sex chromosome, so the heredity is related to sex. Dependent inheritance refers to the fact that although some genes are located on the autosomal denier, they are expressed differently in different sexes due to the action of sex hormones.

Sex-limited inheritance refers to the fact that some genetically controlled symptoms are expressed only in one sex and are not badly expressed in the other sex, and the genes are not necessarily located on the sex chromosomes. All three modes of inheritance are sex-related.

But in the title is generally not, my teacher summed up a sentence for us called "female disease paternity disease" genetics is a more complex subject, her father and son must also have the disease, so to distinguish it from other genetic methods, it will be related to gender, that is, a woman has a recessive genetic disease with x. Wait until you really encounter the problem, start by understanding the nature of heredity, and the question of companion inheritance will give a diagram of at least three generations.

When it comes to the topic of companion inheritance, I have been away from the college entrance examination for many years.

Companion inheritance is mainly for organisms with sex chromosomes, and understanding needs to be done step by step, which is a characteristic of the disease with X recessive, mainly with X inheritance.

Companion inheritance is the way traits controlled by genes on sex chromosomes are inherited. Also known as sexual linkage (genetic) or sexual linkage.

Companion inheritance: Pathogenic genes exist on sex chromosomes, mostly on the X chromosome, so they are also called X-companion inheritance. According to the dominant recessive nature of the pathogenic gene on the X chromosome, it can be divided into two types: X-partner dominant inheritance and X-partner recessive inheritance.

In particular, the latter are more common, such as hemophilia, color blindness, muscular dystrophy, etc. Heterozygous females do not develop disease because she has two X chromosomes, one with a pathogenic recessive gene and the other with a dominant normal gene, so she is only a carrier; But males have only one X chromosome, so one of the pathogenic recessive genes can also occur, often with uncles and nephews suffering from the same disease.

The genotypes of the parents are: 1: AAXB, 2: AAXBY (indicated by the genes A and B: XB).

b, the probability that No. 4 is heterozygous = the probability that No. 1-4 is homozygous = 1-aaxbxb = 1-1 3x1 2 = 5 6

D, No. 5 (aaxbx-) and a B disease gene carrier (aaxby) marriage, the probability of the birth of a boy disease = 1 - the probability of giving birth to a normal boy = 1-a-xby = 1-1 2x1 2 = 3 4, so D answer is wrong.

If you are a student in Shantou, you can take a look at this if you are not good at biology.

I choose DA couple with normal color vision can have a genotype of XBY, XBXB, or XBXB, (B and B are alleles, and color blindness is inherited with X recessive).

If the mother's trait is XBXB, then the child is normal regardless of gender, A pair;

If the mother is XBXB, the girl has a genotype of XBXB or XBXB, which is normal, while a boy may be XBY or XBY, i.e., half normal and half colorblind, hence B pairs;

If the mother is XBXB, the girl has a genotype of XBXB or XBXB, which is normal, but half are carriers;

From the explanations of items A and B, it can be seen that when the mother is XBXB or XBXB, there will be no situation described in D.

d The daughter cannot be color blind because the father is normal and the gene given to the daughter is XA. Must be phenotypic normal.

Genes located on sex chromosomes are always genetically associated with sex, a phenomenon called companion inheritance.

Genes located on sex chromosomes do not follow Mendel's law in heredity, but exhibit the characteristics of companion inheritance. Wrong. Aren't hemophilia and red-green blindness both inherited with sex? Aren't they all made with Mendel's laws? So follow Mendel's laws.

Genes located in the same position on homologous chromosomes control the same trait. Wrong. It may be the same trait or it may be relative.

Genes on sex chromosomes can all control sex. False, this is obviously fake, such as the red-green color blindness gene.

Sex is controlled by sex chromosomes and is not genetically related. Wrong. "Controlled by chromosomes", think about what chromosomes control? It's controlled by genes.

Hope it can help you solve the problem.