I m in my third year of junior high school, and I don t know much about the heredity and variation o

Isn't genetic variation in living things the content of the third year of high school?

Why do you have to learn this in the third year of junior high school?

Isn't biology the end of the second year of junior high school?

I chose biology in my third year of high school...

What is heredity and variation.

Micro Lesson Series丨Junior High School Biology Genetic Diseases and Eugenics.

Solution: This is divided into a variety of situations-

Offspring] Gender: 50 males and 50 females

Traits: If the parents are all AA, the probability of dominant traits (AA, AA) is 75%, and the probability of recessive traits (AA) is 25%.

aa:aa:aa=1:2:1) See Heredity**.

Genetic disease: Chance of onset in boys: Chance of onset in girls: Chance of onset in children: 25%.

Chance of Sick Boy: 25% Chance of Sick Girl: 25% Chance of Sick Child: 50%.

Normal Boy Chance: 12% Normal Girl Chance: Normal Child Machine Filter: 25%.

However, mastering these is secondary, and careful review of the topic is the most important! That's what I once suffered!

I wish you all the best in your high school entrance examination!

1. C (paired, not necessarily the same number, different structure) The chromosomes of different organisms are different, for example, there are 23 pairs of human beings, and 2. A is the same species, and the number of somatic chromosomes is the same, for example, people are 46. However, the structure is different (that is, the gene sequence is different, so the talent shows the difference between men and women, and even if it is a person of the same sex, the genes are different, resulting in differences in human appearance, etc.).

Chromosomes are paired in the cells of any organism (2n). Non-somatic cells, such as germ cells, are not paired and are only half the size of somatic cells (n).

In addition, I don't know if you mean that the gene sequences are different, or the basic units of chromosomes are different (the chromosomes of any organism are composed of proteins and DNA, so it's too complicated to forget it, so you don't understand).

This question examines the concept of heritable variation and non-heritable variation, these two kinds of variation are divided according to the causes, the variation caused by the genetic material is the genetic variation, caused by the external environment, the genetic material has not changed for the non-heritable variation, but the environmental impact of the change of the genetic material will also produce genetic variation, such as artificially treating seeds with rays or drugs, which will cause changes in the genetic material of the seeds, and the offspring bred from these seeds will have genetic variations. However, in general, variations due to environmental conditions do not alter the genetic material and are not inherited. Once the above questions are clear, the answer to this question is clear.

Answer] d.

Variation is ubiquitous in living things. During the replication process of DNA, the parent strand will be incorrectly added, missing, or changed, resulting in mutation. A classic example is sickle cell disease.

For the answer to A, it can be understood that the mutation of the organism leads to the emergence of individuals with new traits. This variation is very detrimental to the individual living organism, but beneficial to the population as a whole. The mutated individuals provide the raw materials for natural selection, which hopefully allows the population to survive in the changed environment.

Therefore, c is also correct.

For d, heritable variation is a variation caused by a change in genetic material; Whereas, non-heritable variations are caused by the environment, and the genetic material does not change.

Asked by: Slipper girl.

Probationary period level 1.

Trait refers to the sum of all the characteristics of an organism. There are many, many traits in any living organism. Some are morphological and structural characteristics, some are physiological characteristics, some are behavioral patterns, and so on.

Genetic variation refers to the fact that the parents of an organism can produce offspring (heredity) with similar traits to themselves, but it is absolutely not exactly the same between parents and offspring, and between individuals of offspring, that is, there are always more or less differences, and this phenomenon is called variation.

Since it's a science book, you shouldn't be very old. A lot of theories are not interesting. The positive side should be a good example of proving genetic variation.

For example, to breed some good seeds by genetic variation, it is to select homozygous for the best traits in the offspring. This can make the melons and fruits more fragrant. Vegetables are even tastier.

Or maybe it was because of genetic variation that humans evolved from apes to humans. I have mastered various techniques.

Understanding genetic variants can overcome certain congenital conditions or alter certain genes. Isn't that what the Human Recombination Project is studying?

Think about anything else

The genetic and variant differences are as follows:

1 Heredity is directed, variation is not.

2 The latter is the source and foundation of the former.

3 Variation is the cause of evolution.

4 Heredity is the phenomenon of similarity between generations, and variation is the difference between individuals of organisms.5 Both heredity and variation are the result of biological adaptation to the environment. Both heredity and variation are universal.

Heritability and variability of organisms exist simultaneously to adapt to changes in environmental conditions, to maintain biological evolution and to produce biodiversity. Heritability of organisms is a manifestation of genetic stability, variability is a manifestation of genetic mutation, and both heredity and variation are universal natural phenomena. Mutation within a certain range is necessary for organisms to produce new genetic traits and new biological species, without mutations, there is no biological evolution, and the biological world cannot move forward, so mutation mutations can also be said to be another function of DNA.