Question

The cells taken from different tissues in the human body, such as muscle cells and liver cells, are structurally and functionally different from each other because
A. They have different number of chromosomes
B. They are expressing different genes
C. They contain different ribosomal subunits
D. They contain different genes

Answer 1

Hint: A group of similar cells performing similar functions make tissues. The tissues make up the organ and the organs make the organ system. The different tissues are made up of different cells.

Complete Answer:
To solve this question, we must know about the genomic level of tissues.
- The multicellular organisms have specialised organs so that they can carry different physiological processes easily.
- Each cell has a nucleus which contains the complete genome.
- The number of chromosomes in an organism is constant irrespective of the different kinds of cells. For example humans have 23 pairs of chromosomes which comprises of 22 pairs of autosomes and one pair of sex chromosomes.
- The DNA of all the cells is identical with similar genes. The expression of genes and the proteins differ from cell to cell in all the tissues. The RNA synthesised in each cell is specific according to the function of the cell to synthesise the kind of proteins.

Thus the correct answer is (B).

Note: The control of gene expression occurs at the transcription level which is due to binding of proteins at specific sites on DNA. The structural gene is not coded as the repressor molecule binds to the operator and blocks RNA polymerase.