High School Compulsory 2 Biology Ask for Help 2, thank you

A-b-:a-bb:aab-:

aabb=9:3:3:

1 The ratio of phenotypes in the text is 9:7, so it is 3:3 in the back

1 merged, that is, in addition to being a and b at the same time, they are all another trait, f1 generation is aabb, and the test cross is hybridized with double cryptography, and there is only one aabb in the case of a and b at the same time, accounting for 1 4 so it is 1:3

The second question is that the probability of the occurrence of four gametes is 10, and the occurrence of homozygosity can only be the same kind of gamete encounter, so there are 1 10*1 10+4 10*4 10+4 10*4 10+1 10*1 10=34 100=34%; It's good to be proficient in this piece, come on.

That formula, you can see for example, ab, only when it meets with the same ab gamete can it be a double pure sum, otherwise there must be heterozygous, so from the mathematical probability of multiplication, the probability of ab is 1 10, and the probability of another gamete ab is also 1 10, and the probability of meeting is the multiplication of two 1 10, and the others are the same, so there will be the above formula, simply put, it is the principle of multiplication and the principle of addition, and the addition of the probability of the last few cases is the answer, understand?

First the first question, the second question is not clue for the time being, I haven't read biology for two years. The first question is that aabb aabb gets 1 2 aa 1 2 aa and 1 2bb 1 2bb gametes; Then according to the free allocation of genes, 1 2 * 1 2 (equal to 1 4) aabb: 3 4 (1-1 4) because there is only one phenotype (that is, containing ab), so you can directly use subtraction later, of course, you can also add and compare one by one, and the result is the same.

The known incidence of albinism in the population is 1 10 000, so the proportion of people with albinism in the total population is 1 10 000. Let the frequency of the causative gene of albinism be q, then there is:

Number of people with albinism Total number = q 2 = 1 10000 Therefore, q = sqrt(1 10000) =.

And because albinism is caused by recessive pathogenic genes, the frequency of albinism gene carriers is 2pq, where p is the normal gene frequency, which is equal to 1-q, i.e. Therefore, albinism gene carrier frequency = 2pq = 2 = approximately.

For a normal man to marry a normal albinism gene carrier, according to Mendelian genetics, the following possible genotypes and probabilities can be listed:

The genotype of the offspring is a combination of the normal gene and the albinism gene

The probability is p q = =.

The offspring genotype is a combination of two albinism genes:

The probability is q 2 = =.

The genotype of the offspring is a combination of a normal gene and an albinism gene:

The probability is 2pq = =.

Therefore, the probability of the offspring having albinism is the combined probability of the two albinism genes, i.e., approximately.

First of all, human chromosomes are divided into two types: autosomes (22 pairs) and sex chromosomes (x and y).

1. Autosomal dominant inheritance refers to the dominant expression of pathogenic genes on chromosomes, and 50% of children have the possibility of pathogenic inheritance. For example, AA is a pair of autosomal genes, and the pathogenic gene is A, and its offspring have a 50% chance of acquiring the disease-causing gene, which is manifested as a certain disease.

2. Autosomal recessive inheritance refers to the recessive expression of pathogenic genes on chromosomes, and 50% of children will acquire the disease-causing gene. For example, AA is a pair of autosomal genes with a disease-causing gene that has a 50% chance of being developed in their offspring, but only if the offspring is AA genotype.

3. Dominant inheritance with X refers to the dominant expression of pathogenic genes on the X chromosome. In general, the incidence is higher in females than in males because females have two X chromosomes, while males have only one.

4. With X recessive inheritance refers to the recessive expression of the pathogenic gene on the X chromosome. In general, the incidence is higher in men than in women, because men need only one x(a) to develop the disease, while women need two xx(aa) to get sick.

5. Y genetic disease refers to the pathogenic gene on the Y chromosome. This genetic disorder is only affected by males because only males have a Y chromosome.

These are single-gene inheritance, often the difference with the accompaniment x is the location of this gene, because most of the lectures are hereditary diseases, so the dominant recessive nature of the pathogenic gene is often discussed, when the individual is heterozygous, the pathogenic gene is dangerous to show the disease, and the recessive is normal phenotype.

often visible: polydactyly, syndactyly, often hidden: albinism; with X: rickets; with x-hidden: red-green color blindness; With y: hirsutism of the external auditory canal.

Changxian: that is, this gene is located on the autosome, as long as there is him, it will show the corresponding traits, so it is called Changxian, Changyin: that is, this gene is located on the autochromosome, and only when the gene is homozygous can it show traits. Everything else is similar!

The number of chromosomes contained in different organism haploids that developed directly from gametes can be different, and it must not be assumed that haploids contain only one chromosome set, or there may be multiple chromosome sets.

Haploid is distinguished from monoploid (an individual whose somatic cells contain a set of chromosomes). Some haploid organisms have more than one set of chromosomes in their somatic cells. The vast majority of organisms are diploid organisms, and their haploid somatic cells contain one chromosome set, and if the original species itself is polyploid, then its haploid somatic cells must contain more than one chromosome set.

For example, the haploid of tetraploid rice contains two sets of chromosomes, and the haploid of hexaploid wheat contains three sets of chromosomes. It stands to reason that it should be called a ploid.

However, there is no requirement for the course standard.

Haploid is relative. For example, in tetraploid organisms, its haploid contains 2 chromosome sets; 6ploid organisms whose haploid contains 3 chromosome sets ......

An organism that contains only one set of chromosomes is called haploid if it is diploid itself, and monoploid if it is not diploid itself.

Organisms that contain only one chromosome set must be haploid, but haploid does not always contain only one chromosome set, haploid is a relative concept, that is, it depends on how many ploids the original organism is, for example, potato is tetraploid, then its haploid contains two chromosome sets, ordinary wheat is hexaploid, its haploid contains three chromosome groups, rice is diploid, and its haploid only contains one chromosome group.

Organisms containing only one set of chromosomes must be diploid, but not necessarily haploid, which is developed directly from germ cells.

There was an accident with this, I forgot about it. Anyway, you understand these and ask the teacher. 1；Germ cells "diploid, tripled, sixfold" such as humans. Banana. Wheat. 2；Bees are important, especially male bees. It is haploidently developed.

It is called haploid, and there is no such thing as a diploid.

Organisms with an even number of chromosomes are not necessarily fertile, if they are heteropolyploid organisms with excitated chains, then they are infertile, for example, if there are three wheat chromosomes and three cotton chromosomes in the cells of a certain organism, then they are naturally sterile.

Having an odd number of chromosomes must be infertile.

The chromosome set is not the same, it can be different in quantity, it can also be different in chromosome species, if it is only different in quantity, then it is not necessarily a species, if it is different in species, it must be a different species. Overall, this statement is false.

Whether an organism is fertile or not depends mainly on whether its chromosomes are all pairs of homologous chromosomes.

In addition, I would like to suggest that you should not be too careful in learning things, and you should not be too careful in some places. The third question you ask is a controversial issue in current teaching, for example, are tetraploid and octaploid watermelons counted as one species? Their offspring are fertile.

By definition, they are a species. This is a big point of controversy, so the college entrance examination will not examine such controversial things.

If you don't understand, you can ask, I hope it can help you from the high school biology answer group.

No, no, it is also imitated as asexual reproduction, such as triploid bananas.

Yes, if the number of chromosomes is different, it must be a different species. Thank you!

I wanted to say a few words, but I saw that 766453276 answer was so good, I'm still a flash person.

1: Alive, without the DNA of the S virus, and the R type has not changed 2: Dead, because the S bacteria were added later.

3: Alive, only DNA, does not die.

4: Live, ditto.

To sum up, select D knowledge points for analysis]: DNA enzyme decomposes the DNA of S-type bacteria, so mice survive; Type S bacteria are lethal, so mice die; The R-type bacteria were killed by heating at high temperature, and then the DNA of the S-type bacteria was added, but the transformation could not occur, so the mice survived. The S-type bacteria were killed by high temperature heating, and the DNA of the R-type bacteria was added, and the mice also survived. The key to understanding is that only the DNA of R-type live bacteria + heat-killed S bacteria can be transformed.

First of all, type S bacteria are toxic, while type R bacteria are not poisonous.

The DNA + DNA enzyme of the S type bacteria is decomposed after the DNA of the S type bacteria is not present, and then the R type bacteria are added, and the mice will not die.

The DNA + DNA enzyme of the R bacteria was then decomposed, and the S bacteria were added, and the S bacteria survived so that the mice died.

The high temperature kills the R bacteria, and then it is useless to add the DNA of the S bacteria, because there is no protein, and the high temperature denatures the proteins, and the mice are alive.

The high temperature kills the S-type bacteria, and the DNA of the S-type bacteria is also killed in the high temperature, and the DNA mice with the R-type bacteria are also alive.

Pick D. The key to this topic is to see if there are live S-type bacteria at the time of final injection (note that not only DNA, but also the complete cellular structure), because live S-type bacteria can kill mice.

1. The DNA of S-type bacteria will be hydrolyzed by DNA enzymes, and the added R-type bacteria cannot be converted into S-type bacteria, that is, there are only active R-type bacteria in the end.

2. The DNA of type R bacteria will be hydrolyzed by DNA enzymes, but after adding type S bacteria, there are active type S bacteria, and mice will die.

3. The DNA of type R bacteria will be hydrolyzed by DNA enzymes, and the DNA enzyme will be denatured by cooling after high temperature heating.

4. The DNA of type S bacteria will be hydrolyzed by DNA enzyme, and the DNA enzyme will be denatured by cooling after high temperature heating.

Do you understand?

Logical reasoning is a method of reasoning from general to particular. As opposed to "induction". The connection between the inferential premise and the conclusion is inevitable and is a kind of confirmatory reasoning.

So it can't be said that the use of letters does anything for logical reasoning, but it can be said that it does what it does for experiments.

If it is used for experiments, it is possible to visually distinguish which is the dominant gene (uppercase letter) and which is recessive (lowercase letter) in the form of letters.

When analyzing the chart, it is easy to calculate the proportion of each gamete, and it is easy to estimate the proportion of offspring that are dominant or recessive.

Ability to distinguish between dominant and recessive genes. The ratio of heterozygous and homozygous can be derived from formulas.

The experimental results can be displayed relatively clearly.