Question

 

17. During transcription, RNA polymerase adds new nucleotides

1. at the carboxy-terminal of the elongating chain
2. at the amino-terminal of the elongating chain
3. at the 3` end of the elongating chain
4. at the 5` end of the elongating chain
5. at both 5` and 3` ends of the elongating chain

 

17. Different cells of an organism can produce different types of proteins because

1. They have different genes in different cells
2. Same genes are present in all cells
3. Differential expression of genes in different cells
4. Same genes are expressed in all types of cells
5. None of the above

Answer 1

A) option C - at 3' end of the chain

RNA polymerase always builds a new RNA strand in the 5’ to 3’ direction. That is, it can only add RNA nucleotides (A, U, C, or G) to the 3' end of the strand.

Different cells of an organism can produce different types of proteins because of - Differential expression of genes in different cells

Most living things are composed of different kinds of cells specialized to perform different functions. A liver cell, for example, does not have the same biochemical duties as a nerve cell. Every cell of an organism has the same set of genetic instructions, but different types of cells have different structures and biochemical functions. Since biochemical function is determined largely by specific enzymes (proteins), different sets of genes must be turned on and off in the various cell types. This is how cells differentiate. This is the process of cell-specific expression of genes.