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BB hybridizes BB

F1: for bb then bb x bb b 50% b 50% f2:bb:bb:bb=1:2:1 remove bb bb=1 3 bb=2 3

f3: bb x bb=1 3*1 3=1 9 bb x bb=1 3*2 3*2=4 9 All are gray.

bb x bb (gray body) = 2 3*2 3*3 4=3 9 bb x bb (black body) = 2 3*2 3*1 4=1 9

So: gray body: black body = (1 9 + 4 9 + 3 9): 1 9 = 8:1

A simple way:

f0: bb bb

f1:bb bb

f2:bb bb bb bb

Remove BBF2: BB BB BB

For a BB offspring all ash.

For a BB, the probability that the offspring is black (bb) is 2 3 * 1 4 = 1 6 BB accounts for the total number of 2 3, then the black (BB) accounts for the total number of offspring 1 6 * 2 3 = 1 9 gray: black = 8:1

Genotype of F1 generation: BB

F2 genotypes: bb, bb, bb

Remove the black body Drosophila, i.e. the genotype BB and BB, F3 generation: two different genotypes are self-crossed and crossed:

bbxbb bbxbb bbxbb

Only three genotypes of offspring will be produced, but the ratio of numbers should be 12:1

Parent: bb*bb

f1:bbf2:1bb 2bb 1bb (culling)f3:

bb or bb: 1 3*1 3*1 (bb*bb) + 1 3*2 3*1 (bb*bb) + 2 3*2 3*3 4 (bb*bb) = 2 3

bb: 2 3*2 3*1 4 (bb*bb) = 1 9 gray than black: 6:1

I counted 6:1

Summary. The heart is made up of four chambers, which are the left and right atria and the left and right ventricles. Between the atria and ventricles there is a valve called the atrioventricular valve, which controls the direction of blood flow.

The atria are the upper part of the heart, one on the left and one on the left. The walls of the atria are thin and their main function is to receive venous blood and send it into the ventricles. The interior of the atria has some small muscles called the atrial muscles, which contract to help send blood into the ventricles.

The ventricles are the lower part of the heart, one on the left and one on the left. The ventricles have thick walls and their main function is to push blood to various parts of the body. The ventricles have some large muscles inside called the ventricular muscles, and their contractions can create a powerful force that pushes blood throughout the body.

The atrioventricular valve between the atria and ventricles is made up of two leaflets, the tricuspid and mitral valves. The tricuspid valve is located between the right atrium and the right ventricle, and the mitral valve is located between the left atrium and the left ventricle. These two valves control the direction of blood flow and prevent blood from flowing backwards.

One by one, oh kiss.

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The practice of this question is that the heart is made up of ventricles and atria and the cardiac conduction system, and its function is mainly to power the body's blood circulation. 1. The structure of the heart is composed of two groups of atria and ventricles, namely the left atrium, the left ventricle and right atrium, and the right ventricle. The four chambers of the heart are separated by a cardiac septum, and the atrioventricles are connected by a one-way valve, with the mitral valve between the left atrioventricles and the tricuspid valve between the right atrioventricles.

There is a pericardial wrap on the outside of the heart. Because the left and right atrioventricles are responsible for different circulation, the left atrioventricle is larger than the right atriovenle, and the myocardial wall is thicker. In addition to the atrioventricular structure, the heart also has a cardiac nervous system, which is composed of sinus node, internodal bundle, atrioventricular node, and atrioventricular bundle.

2. The function of the heart. As the most important part of the circulatory system, the heart provides power for the body's blood circulation, so that blood flows continuously through the body's blood vessels.

The heart is made up of four chambers, which are the left and right atria and the left and right ventricles. Between the atria and ventricles there is a valve called the atrioventricular valve, which controls the direction of blood flow. The atria are the upper part of the heart, one on the left and one on the left.

The walls of the atria are thin, and the main function of the stockings is to receive venous blood and send it into the ventricles. The inner part of the atria has small muscles called the atrial muscles, which contract to help send blood into the ventricles. The ventricles are the lower part of the heart, one on the left and one on the left.

The ventricles have thick walls and their main function is to push blood to all parts of the body. The ventricles have some large muscles inside called the ventricular muscles, and their contractions can create a powerful force that pushes blood throughout the body. The atrioventricular valve between the atria and ventricles is made up of two leaflets, the tricuspid and mitral valves.

The tricuspid valve is located between the right atrium and the right ventricle, and the mitral valve is located between the left atrium and the left ventricle. These two valves control the direction of blood flow and prevent blood from flowing backwards.