High School Biology Judgment Methods on Companion Inheritance

Solve the problems that high school biology students are prone to.

Dark brown teeth, dental enamel dysplasia, pendulum nystagmus, mouth, face, finger syndrome, lipoma, syringomyelia, keratosis of spinous hair follicles, antivitamin D rickets, etc.

Companion inheritance is the process of inheritance in which some traits of the offspring are controlled by genes on the chromosomes of the sex lease bond, and normal dominant refers to autosomal dominant inherited diseases. Determine whether the disease is dominant or recessive, and the parents are affected, and if the child is normal, it is dominant, and determine whether the disease is autosomal or accessory.

If it has been determined that it is recessive, the father is positive and the daughter is autosomal inheritance. The mother suffers, and the son is also autosomal inherited. If it has been determined that it is dominantly inherited, the paternal and the daughter are normally autosomal dominant. Maternal children are also inherited in an autosomal dominant manner.

1. Observation 3 and 4 both have nail disease, but none of the offspring have nail disease, indicating that nail disease is dominant (there is a middle generation but no dominant), because if it is hidden, the offspring will inevitably have nail disease. Neither 3 nor 4 has disease B, but the offspring have disease B (7), so disease B is recessive.

2. Dominant inheritance depends on male diseases, and male patients and mothers are positive and non-partnered. These two sentences are judged together. "Male" refers to the parents, i.e., a boy born to both parents. 2 is normal, 4 is diseased, so dominant inheritance of nail disease is not inherited with sex, it is autosomal inheritance.

If you have B disease, but your offspring have normal 9, it means that B disease is not inherited with Y, but may be inherited with X, or it may be autosomal inheritance.

For example, 3 and 4 (both have nail disease) in this diagram give birth to 8 (is female and does not have nail disease), this is"There is no middle birth", which is inherited in an autosomal dominant manner.

Dominant inheritance refers to male chromosomes with only one X chromosome, and if it is a dominant sexually transmitted disease, it will definitely be expressed.

Companion inheritance refers to the inheritance of sex with sex, which is related to sex.

Autosomal inheritance is inheritance that is not related to sex.

It means that the parents are sick, but the children born are not sick, then the disease is dominantly inherited. Dominant looks at male disease, male mother (female) is not partnered, which means that dominant inheritance depends on the diseased male, if the mother or daughter of the diseased male is diseased, the inheritance is not companion inheritance, it is autosomal inheritance, and there is a recessive out of nothing, recessive to see female disease, female disease male is not companion, this is the same as the above sentence of understanding. There is also the fact that companion inheritance is mainly related to sex, while autosomal inheritance has nothing to do with sex, so the mantra taught by the teacher is judged from sex inheritance.

There is a mantra that makes something out of nothing is hidden, and giving birth to a girl who is sick is often hidden.

There is no dominance in the middle birth, and the disease of the birth of a girl is often obvious.

In the recessive inheritance with X, "the mother and the child will be sick, and the female and the father will be sick". The reason is that the mother has the disease, and both of her X chromosomes carry a recessive pathogenic gene, and there must be a recessive pathogenic gene that is passed on to her son (genotype XY) along with an X chromosome, and the son's Y chromosome has no relative equivalent action, and a recessive pathogenic gene causes the male to manifest the disease. In the same way, when a daughter is sick, both of her X chromosomes carry a recessive pathogenic gene, and there must be a recessive pathogenic gene that was passed on to her by her father (genotype XY) along with an X chromosome.

In the dominant inheritance with x, "the mother will be sick, and the father and daughter will be sick". The reason is similar, in the pedigree with X dominant, if a man suffers from a sex X dominant genetic disease, his mother and his daughter should be the patient.

In Y-chromosome genetic diseases, it is manifested as a disease that only occurs in males, and it is passed from father to son, from child to grandchild, and there is no end of children and grandchildren.

The gene for Caeugene is A

a Color blindness. bb

Autosomal recessive disorders occur in 1% of the population, so the gene frequency of 1 percent a is 1 10

A is 9 10

So the wife is AA and the husband is.

AA (81 99) or.

aa（18/99）

For the color blindness gene, the wife is XBXB

The husband is xby

7% of this question is a distractor).

The probability of a child suffering from a common hidden disease is:

The probability of color blindness is 1 2 * 1 2 = 1 4

Therefore, suffering from two diseases at the same time is 9 198 * 1 4 = 1 88

Select A. Occult disease is denoted by a,a, and color blindness is denoted by b,b. The mother is AAXB, and the father is AA or AA, the details are not known.

But it has to be xbyIt is only possible to give birth to a child with two diseases at the same time if the father is aaxby. What are the odds that a father is aaxby?

aa=1%, so, a=

a=。However, it is known that the paternal phenotype is normal, so it cannot be AA, so the actual AA probability is AA (AA+AA)=

The probability of developing common hidden disease is 1 4, and the probability of color blindness is 1 4So both diseases are 1 16

So the final answer is 1 16 times 2 11 equals 1 88.

The mantra is made up by people, and it is best to understand it yourself.