Biology for the third year of high school, biology for the third year of high school

1.The purine base in a certain organism accounts for 44% of the total, and the pyrimidine base accounts for 56% of the total, the organism cannot be:

a.Tobacco mosaic virus bacteriophage.

c.Escherichia coli DYeast and humans.

Select A Analysis: According to the DNA molecule base pairing rules: A is paired with T, G is paired with C. Therefore, in the double-stranded DNA molecule, the purine base number (A + G) must be equal to the pyrimidine base number (C + T), that is, each accounts for 50%.

From the inscription, the nucleic acid of the organism must not be DNA, but RNA

Tobacco mosaic virus: single-stranded RNA; T2 bacteriophage, Escherichia coli, yeast, and human: all double-stranded DNA

Yes, after translation, the mRNA is broken down into individual nucleotides.

However, the question asks: the consumption of the labeled substance in the medium. Cell differentiation requires the synthesis of a large number of tissue-specific proteins, and DNA must simultaneously transcribe a large amount of mRNA for translation.

As a result, a large amount of uracil (nitrogen-15)-labeled uracil in the medium is consumed.

Depletion refers to the uptake of uracil ribonucleotides from the medium into the cells.

Landlord, please pay attention to the base pairing rules: a is paired with t(u); G is paired with C. Don't get confused.

Since there are n g+cs on mRNA, there are also n c+gs on one strand of the template DNA molecule. In the same way, the number of A+T on this DNA strand is equal to the number of U+A on mRNA, i.e., m-n. Then the number of t+a on the other strand of DNA is also m-n.

So, the A+T number of the entire template DNA molecule is 2 (m-n).

The number of water molecules removed is the number of amino acids minus the number of peptide chains, i.e. (m3)-2

The genetic material of tobacco mosaic virus is RNA, which is the test center of the college entrance examination.

c The genetic material of E. coli is DNA. The genetic material of eukaryotes and prokaryotes is DNA, that is to say, the genetic material of bacteria and fungi is DNA, which is also an important test point in the college entrance examination.

Please keep in mind the landlord.

2。Well, what you said is not unreasonable, but after mRNA completes its mission, it may be broken down into nucleotides to continue to synthesize new molecules, or it may be completely degraded into five-carbon sugars, phosphoric acids, and bases.

It is a single strand, if there are m bases in mRNA, it means that the two strands of the template DNA molecule have m bases respectively, one of the strands that transcribe mRNA becomes a strand, and the other is a B strand, then the B strand is exactly the same as mRNA, there are also n g + c, there are m - n A + T, A in the B strand (adenine) and A in the A strand are equal in number (at pairing).

In the same way, the T in the B strand is equal to the A (adenine) in the A strand, so the A + T in the A strand is equal to the T + A in the B strand, which is equal to M-N, so the total number of A+T in the DNA is 2 (M-N) in the AB chain.

I think the landlord's idea may be a little messy.

Please note that it is at pairing, GC pairing, you may be used to doing questions, always do A+G=T+C, but please note that it is not A+T=G+C, so it is impossible to judge the number of A+T in any strand of the DNA molecule based on M G+C on mRNA alone.

1'The purine base accounts for 44% of the total number and the pyrimidine base accounts for 56% of the total number in a certain organism'

The genetic material of the organism is not a DNA duplex.

Select b c d

Tobacco mosaic virus: single-stranded RNA;

T2 phage, E. coli, yeast, and human: double-stranded DNA

2 After the translation is completed, the broken mRNA becomes a single nucleotide, which can be said to be unconsumed.

But it's not necessarily all mRNA that is transcribed and synthesized, there are other RNAs, to name a few:

The RNA that makes up ribosomes and the tRNA that transports amino acids are consumed for synthesis.

A medium contains 15N (nitrogen-15)-labeled uracil ribonucleotide and generally does not break down.

Another example is some enzymes (the chemical nature is RNA).

3 First of all, I would like to mention two concepts. The DNA used to transcribe synthetic RNA is called a template DNA strand (or intentional strand).

But the question is that the template DNA molecule is two strands

An mRNA molecule has m bases, and the template DNA molecule used for transcription has at least 2M bases.

There are n g+c of mRNA, mRNA molecule A+U is M-N, and the template DNA strand A+T is (M-N).

The tobacco mosaic virus genetic material is RNA

c.Bacteria, the genetic material is, of course, DNA

Only the genetic material of the virus is divided into DNA and RNA, and the rest is DNA

dThe fluid in the blister** is formed by the exudation of the capillary artery to the blood vessel, and it is eventually absorbed back into the capillary vein or lymphatic vessels, and finally circulates back to the right atrium. A blood circulation process is formed.

d...

The blisters are tissue fluid, which is absorbed by the capillary capillaries.

d Capillary and the like are more absorbent.

The second question will not be done...

The selection of acres is a, and the red and green hail color blindness is accompanied by x recessive heredity, and the analysis is shown in the figure.

It should be the fourth answer.

The second option is B, I feel that option C is normal, not overimmunity.

Select A for question 1. Heating denatured proteins only changes the spatial structure, but the peptide bond is not broken, so it can still undergo chromogenic reaction with the biuret reagent. Question 2 selects D, this transport does not use carrier proteins, and belongs to free diffusion.

Question 3 option B, ecosystems should include microorganisms in addition to flora, fauna and inorganic environments. Question 4 selects D, since the decreasing rate of A and B is the same, it can be judged that the concentration of the solution of A and B is the same, and then the length of the potato strips in A can return to the initial length, indicating that the solute of solution A can enter the cell. Question 5 choose B, for the same antigen, a B cell can only produce one antibody.

Question 6: Select A.