6. If the coat color of mammals is determined by three pairs of independently distributed alleles located on the autosome, then the enzyme encoded by gene A can turn yellow into brown; The enzyme encoded by B gene can convert brown pigment into melanin; The expression product of D gene can completely inhibit the expression of A gene; The expression products of the corresponding recessive alleles A, B and D do not have the above functional departments &: Net. If two homozygous yellow breeds of animals are used as parents, F 1 is yellow, and the number ratio of yellow: brown: black = 52: 3: 9 appears in F2, then the hybrid parent combination is
A.AABBDD×aaBBdd, or AAbbDD×aabbdd.
B.aaBBDD×aabbdd, or aaBBDD×aabbdd
C.aabbDD×aabbdd, or aabbDD×aabbdd
D.AAbbDD×aaBBdd, or AABBDD×aabbdd
The answer to this question is D.
7. The following statement is wrong.
A. carbohydrates can also be called carbohydrates.
B. vitamin d can promote the body's absorption of calcium.
C protein is a substance composed only of carbon, hydrogen and oxygen.
D selenium is an essential trace element for human body, but it should not be ingested too much.
The answer to this question is C.
9.a, B, C and D are short-period main group elements with increasing atomic numbers. In the network, the total number of electrons outside the nucleus A is the same as that outside the atom B; The cycle number of c is the same as the family number; D and A belong to the same family. The following statement is correct.
A. Atomic radius: d>c>b> Among the four elements, B is the most metallic.
The hydrate of C.c oxide is a strong base, and the oxidation of D.d is stronger than that of a.
The answer to this question is B.
The above are some of the questions and answers in the two-volume science comprehensive examination paper of the national college entrance examination for reference only.