Seek answers to three high school compulsory two biology questions

1 4 Cultured for three generations yields 8 DNA, two of which have N15 on one strand

600 1400 bases, then there are 700 a+t on one strand, g+c=2 5, so a + t=200 on one strand, and a+t=200 on the other strand, a=t, so a DNA has 200 t, and it takes 600 t to replicate twice, and 3 new dna

4500 a=t=200 a, accounting for 20% There are a total of 1000 a+t=400 g+c=600 g=c c=300 a DNA has 300c, replicates 4 times, and adds 15 DNA, which requires c=4500

The key to the first question is DNA, which is not a chromosome, the first generation 1 2, the second generation 1 4, and the third generation 1 8

1 4, DNA is double-linked, cut is semi-reserved replication, the parental N15 double strands are, after three generations there are 8 DNA molecules, but only 2 N15 chains.

T 1400*2 7*1 2 200 in one DNA, 4 copies twice, but there was originally one, T 700*3 2100

C 200 in a single unit, total C 300 * [16 1] 4500

f:bb

bbf1:bbf2

1/3bb2/3bb

1 3+2 3*3 4):(2 3*1 4)=(1 3+1 2):1 6=(2 6+3 6):1 6=5:1 So the first question b

f：aabbf1:1/4aa

2/4aa1/4aa

1/4bb2/4bb

1/4bb1/16aabb

2/16aabb

1/16aabb

2/16aabb

4/16aabb

2/16aabb

1/16aabb

2/16aabb

1/16aabb

Because genes A or B are homozygous and cause embryo lethality to 2 16AABB 4 16AABB

1/16aabb

2/16aabb

So the ratio of genotypes is 4:2; 2；1

The question gives a phenotypic ratio of 2:1

So the problem phenotypic ratio for this question is wrong.

It should be changed to genotype ratio.

In a genetic experiment with a pair of relative traits, the following description is incorrect (b).

a.If the offspring are crossed with different shapes, and the offspring have two shapes, it is impossible to judge the dominant recessive trait and the genetic factor composition of the two parents.

b.If two parents with the same trait are crossed, and the offspring only appear in the same trait of the parent, then both the parent and the offspring are homozygous.

c.If two parents with the same trait are crossed, and the offspring has a different trait from the parent, the parent is heterozygous.

d.If a parent is self-bred, and the offspring have two traits, and the trait segregation ratio is 3:1, the offspring that account for 3 4 show dominant traits.

Such as bb x bb

A couple with double eyelids had a total of four children, three single eyelids and one double eyelid, and the best explanation for this phenomenon is (c).

1 Conform to the law of segregation of genes bThis inheritance does not conform to the law of segregation of genes.

c.The couple had the possibility of developing a single eyelid in each fetus dThe single eyelid gene was swapped with the double eyelid gene.

Just like the gender, the first birth of a boy and the second birth of a boy and a girl are possible.

The gray (g) to the white (g) of the pea seed coat is dominant, and the f1 (heterozygous) is now planted and continuously self-crossed. The statement in question is incorrect (d).

The seed coat of the seeds on the plant is gray.

There are three types of cotyledon genetic components of seeds produced on plants.

The seed coat of the seeds on the plant is gray:white = 3:1

The probability that the cotyledon genetic composition of the seeds produced on the plant is homozygous is 1 2

Should be greater than 1 2

In order to observe the trait segregation of pea plants, it is necessary to observe the second generation of children at least until the first year (c.). ）

a.A bII cIII DFour.

The seeds of the second generation of children only grow into plants in the third year.

1 option b If the parents are all heterozygous, e.g. bbThen the offspring will appear bb, bb, bb 3 genotypes, of which the first 2 traits are the same as the parents, but the second is not homozygous, and the parents are not homozygous.

2 choose c, single eyelid and double eyelid are a pair of relative traits, so the gene that controls their traits is an allele. If the gene for a single eyelid is AA, and the gene for both eyelids is AA, then the genotype of the parents may be AA, or it may be AA and AAThe former has a separation ratio of 3 to 1 and the latter has a 1 to 1 ratio

So A is wrong.

3.The cotyledons are developed from the zygote, that is, the cotyledons of F1 are the genetic components of F2, because we can judge by biological totipotency that the genes in each cell are the same. So the title is not wrong, so B is right, and GG is heterozygous.

3 genotypes. So the cotyledons on F2 is the genotype of F3, because the pea is a self-inbred plant, so we can calculate the ratio of F3 through the gene ratio of F2, that is, 1 4 AA + AA + AA + have, AA has, AA has.

4 I broke down, there is a problem with the question of this question. Pick B. First of all, in the first year, we crossed the heterozygous F1AA from the female parent P, (because of the trait separation experiment, so we need to separate different traits from the unified trait in order to achieve the experimental purpose), and then in the second year, we self-crossed the first generation F2 from F1, at this time the shape separation has occurred, so it only takes 2 years.

Why the question still asks the child 2 generations for this key hint, despise the teacher.

1. Choose B, in this case, it is possible that one is zygosis bai and the other is heterozygous.

2. Select DUC, from the question condition

See, the probability of double eyelids in offspring is dao3 4 and single eyelid is 1 4, but each birth is random, and there is a possibility of both single eyelids and double eyelids, and the proportion cannot be obtained in the case of too few samples.

3. Choose B, because the condition given in the title is to study the seed coat, and the genetic composition of the cotyledons is not clear.

4. Choose B, and the second year is the seed produced on the F1 generation.

1 b 。If genes a and a are appointed, then item a corresponds to aa aa aa, aa or aa aa aa, aa; then item b is inconsistent with aa aa aa aa and aa. Then the c and d terms symbolize the concept of round trait separation. Answer.

The impression is 1-(1 2) n ??

Sit back and wait for the answer, and neither will I.

This is a college entrance examination question in Beijing.

The last sentence of the stem: 1Support Mendelian inheritance mode 2If you don't have the answer to fusion inheritance, you should choose C

Option A can only indicate that the safflower trait is not fused with the white flower trait.

But because there is no trait separation ratio.

So there is no way to support the Mendelian way of inheritance.

You see, if the safflower is AA and the hundred flowers are AA, then the offspring generation is all AA, which is in line with the above topic. But what if the safflower parent is AA.

* [3*10 (-21) 18]= = 100, water molecules[3*10 (-21) 18]= find the number of moles of water and multiply by Avogadro's constant to find the number of water molecules.

100 water molecules so there are 100 peptide bonds.

There are two peptide chains, so there are 102 amino acids.

Each amino acid is encoded by 3 bases.

So mRNA has at least 306 bases.

Whereas gene DNA is double-stranded, so there are 612 bases, i.e., 612 deoxynucleotides.

3*10-21g18g* is 100 H2O, each peptide chain generates 50 H2O, that is, there are 51 amino acids, each nucleotide has a codon to determine, and a codon has three deoxyribonucleic acid, and a total of 51*2*3=306 deoxyribonucleic acid, in addition, if the promoter and terminator are considered, more deoxyribonucleic acid is needed, and secondary schools should not require it.

b. Plants contain a large amount of K, which leads to a large amount of K in our herbivorous foods;

Through the relationship of the food chain, our various carnivorous foods also contain a large amount of K;

Because of 1 and 2, we can get enough K from food every day;

Everyone must know that the chemical elements that make up plants contain a lot of K, and the textbooks do not say whether or not they contain Na or how much Na they contain. You can imagine that the amount of Na in plants is many times less than that of K;

The amount of Na in our herbivorous and carnivorous foods is much lower than that of K;

Therefore, it is NA that we tend to lack, not K

When the outside temperature is low, the human body relies on the strengthening of metabolism to maintain body temperature, such as shivering, etc., and always maintains the temperature level of the human body's internal environment. That's why people can also be called thermostatic animals.

Question 1a, because sodium salt belongs to eating more and eliminating more, eating less and eliminating less, and not eating and not excreting. Potassium salt belongs to eating more and excreting more, eating less and excreting less, and excreting without eating. Therefore, when the patient is unable to eat, potassium salt should be supplemented.

Question 2b, pay attention to the topic and strengthen metabolism. There needs to be neurohumoral regulation, and that's only hypothermia. You can look up the textbook, there is an example of this.