核糖体由_____组成
A: Only RNA
B: Only proteins
C: Only DNA
D: RNA and proteins
A: Only RNA
B: Only proteins
C: Only DNA
D: RNA and proteins
举一反三
- In positive regulation, most of the genes are usually inactive (that is, RNA polymerases do not bind to the promoters) and the cell synthesizes only the activator proteins needed to promote transcription of the subset of genes required in the cell at that time.
- Proteins are the principal constituents of cells and determine not only cell structure but also cell function.
- Which of the following statements are correct ( ) A: In eukaryotes, a gene can encode different proteins, but a mature mRNA chain encodes only one protein. B: The function of the promoter is affected by both the DNA sequence and its conformation. C: TFs help RNA polymerase recognize the promoter. D: In DNA biosynthesis, semi-reserved replication and semi-discontinuous replication refer to the same concept.
- Which of the following statements about non-coding DNA is true ()? A: DNA sequences that do not encode proteins B: DNA sequences that do not encode RNA and proteins C: DNA sequence without function D: DNA sequence without phenotype after deletion<br/>[单选题][2分][难度3]
- 1. Which base is found only in RNA but not in DNA? A．U B．A C．C D． T A: A B: B C: C D: D