Question 1: Is the external double eyelid controlled by homozygous dominant gene? Double eyelids are dominant genes, while single eyelids are invisible genes. To give a very simple example, for example, the genes of double eyelids are big A and small A, then the combination of aa and aa is double eyelids, and Aa is single eyelids. According to this ratio, the ratio of double eyelids to single eyelids should be 3: 1. If the mother in a family has a single eyelid, then she is the aa gene, and the father may be the Aa or Aa gene, but if both their children have single eyelids, it means that the father must be AA, because the mother can only provide the small A gene, and the child is the single eyelid, that is, the AA gene, which means that your father must provide you with the small A gene. He has double eyelids, so he has the big A gene. So he is the dominant gene of A, and the recessive gene of A is Aa. As mentioned earlier, the big A is visible, but the small A is invisible, so when the big A and A are combined, they show the characteristics of visible genes, and with the invisible gene small A, they show double eyelids. In other words, parents have single eyelids, and children must have single eyelids.

Question 2: Why are double eyelids controlled by dominant genes? In fact, single pairs are determined by parents' genes, and double eyelids are controlled by dominant genes, that is, genotype Aa or AA determines double eyelids; Single eyelid is controlled by recessive gene, that is, genotype aa determines single eyelid. The generation of single eyelid and double eyelid is related to a levator palpebrae superioris muscle of human upper eyelid. The formation of double eyelids is due to the fibers of levator palpebrae superioris muscle extending into the subcutaneous tissue, and the muscle contraction makes the skin at the attachment shrink, which constitutes skin folds, namely double eyelids, commonly known as double eyelids; The single eyelid lacks this levator muscle fiber attached to the skin, so there is no wrinkle. If a person's genotype contains the dominant gene A that controls double eyelids, then his trait should generally be double eyelids. However, in the process of individual development, due to the modification of other genes or the influence of complex factors such as internal and external environmental conditions, the development of muscle fibers of levator palpebrae superioris may be incomplete, resulting in one eye with a single eyelid and the other with a double eyelid; Others show double eyelids at a certain stage and single eyelids at a certain stage.

It can be seen that the inheritance of this trait of eyelid is influenced by complex factors such as genes and internal and external environmental conditions. In order to answer your question clearly, you can consider two situations:

1, excluding the influence of complex factors such as internal and external environmental conditions, only considering the role of genes:

1/2: Because the single eyelid is recessive, and because a child with a single eyelid is born, the couple's traits are aa and aa, so the probability of having another child with Aa is 1/2.

2. Considering the interaction of genes, internal and external environmental conditions and other complex factors, the situation is much more complicated and the probability cannot be solved. If you are a middle school student, you can know that this situation exists and you don't need to delve into it. You can master the first situation.

Double eyelid incision refers to the method of cutting the eyelid, removing muscle and fat, removing loose skin according to the situation, and connecting the dermis with levator palpebrae superioris, which supports the eyelid. Incision method is suitable for single eyelid with thick or fat, single eyelid with different sizes or ptosis. Double eyelid surgery: Also known as pc, polymer double eyelids, three-point positioning and five-point positioning, without cutting the skin, just use a suture to fix several places along the drawn double eyelid line to make double eyelids. Weifang medical college plastic surgery hospital

Question 3: What does it mean that double eyelids are superior to single eyelids? Is double eyelid dominant or single eyelid dominant? Double eyelids are dominant. Capital letters are dominant, and lowercase letters are invisible. There are double eyelid aa and Aa single eyelid AA.

Hope to adopt

Question 4: Husband's double eyelids. Is his dominant gene aa or aa? Biologically, double eyelids are dominant genes and single eyelids are recessive genes.

For example, the genes controlling single eyelid and double eyelid are big A and small A respectively, then the combination of aa and Aa is double eyelid, and AA is single eyelid. So your husband's double eyelid dominant gene should be Aa or AA.

Question 5: Is double eyelid a recessive gene? Double eyelids are determined by dominant genes, expressed in capital letters, and the gene in cells is AA; Single eyelid is determined by recessive gene, expressed in lowercase letters, and the intracellular gene is aa. sea

2. The gene that controls the black hair of guinea pigs is dominant gene (A), and the gene that controls the white hair of guinea pigs is recessive gene (A).

3. Systemic albinism belongs to autosomal recessive inheritance. Localized albinism is autosomal dominant inheritance.

4. Dominant gene control in congenital deafness.

5. Dominant gene control of color blindness.

First, autosomal dominant genetic diseases

1, polydactyly and syndactyly (toe)

2. Erythropoietic anemia

3. Multiple familial colonic polyps

4. Polycystic kidney

5. Congenital achondroplasia

6. Congenital osteogenesis hypoplasia

7. Retinoblastoma

Second, autosomal recessive genetic diseases

1, albinism

2, phenylketonuria

3, galactosemia

4, mucopolysaccharide storage disease

5. Congenital adrenal hyperplasia

X-linked dominant genetic disease

1, anti-vitamin D rickets

2. Familial hereditary nephritis

X-linked recessive genetic disease

1, hemophilia a.

2, hemophilia B.

3, color blindness.

4. Progressive muscular dystrophy.

Don't recite this, it depends on the topic, and push it backwards according to the conditions of the topic! If the topic is to give a very biased gene or replace it with letters casually, how to recite it?

Dominant genes are heritable in AA and AA.

Recessive genes can only be inherited in aa.

Question 6: Why are double eyelids dominant genes and single eyelids recessive genes? You can consult Xue Jiajin Company.

Question 7: Can double eyelids be inherited? One: parents' double eyelids 1. Both parents have dominant genes, namely AA and AA patterns. No matter how they are combined, the genetic pattern of children is AA, and the heritability of double eyelids is 100%. 2. One parent carries recessive genes, namely Aa and AA patterns. The genetic pattern of children may be: Aa, Aa, AA, AA. The heritability of double eyelids is still 100%, but it may carry recessive genes of single eyelids. 3. Both parents have recessive genes, namely Aa and Aa patterns. The genetic pattern of children may be: aa, Aa, Aa, AA. The heritability of double eyelids is 75%. Two: Are both parents with single eyelids and double eyelids related to heredity? There is only one possible genetic model for parents, namely aa and aa. There is only one possibility for a child's genetic model, namely aa. So the heritability of double eyelids is zero. Three: double eyelids of one parent 1. The parental gene patterns are aa and AA. The genetic patterns of children may be: Aa, Aa, Aa, Aa. The heritability of double eyelids is 100%, but it will carry recessive genes. 2. Are double eyelids related to heredity? The genetic patterns of both parents are aa and Aa. The genetic pattern of children may be Aa, Aa, aa, aa. The heritability of double eyelids is 50%, and both of them carry recessive genes.

Question 8: Isn't double eyelid a dominant gene? Double eyelids are dominant genes, while single eyelids are recessive genes.

Big A and small A, and then combine aa, Aa is double eyelid, AA is single eyelid. According to this ratio, the ratio of double eyelids to single eyelids should be 3: 1.

For example, if your mother has a single eyelid, it must be aa gene, and your father can be aa or Aa, but if you have a single eyelid, it means that your father must be Aa, because your mother can only provide the small A gene, and you are a single eyelid, that is, AA gene, which means that your father must provide you with the small A gene, and he is a double eyelid. He has a big A gene. So he is a dominant gene plus a recessive gene, and the small A is Aa. As mentioned earlier, big A is dominant and small A is recessive, so when big A and A are combined, they show the characteristics of dominant genes, just like your father, who has recessive genes, but shows double eyelids.