Working in pairs discuss these questions with your partner. Then scan the text to find the answers and compare them with your discussion.

1. Is cell division essential to life?

2. What is the basis of reproduction in every organism?

3. What provides continuity between one generation of cells and the next?

4. How manychromosomes does each human cell have?

■ Read the given text and make your essential assignments:

One of the most important concepts in biology is that cells arise only by the division of existing cells. Cell division is essential to all life. It enables a multicellular organism to grow and to replace worn out or damaged cells. It is also the basis of reproduction in every organism. Cell division starts with the division of the nucleus. There are two forms of nuclear division: mitosis andmeiosis.

Chromosomes: carrying information

Chromosomesare the structures that provide continuity between one generation of cells and the next. Their name comes from the Greek: chroma = coloured, soma = body, because of their affinity for certain stains used in microscopy. Chromosomes consist of DNA, the genetic material of the cell, wrapped in protein. They become visible in the nucleus where the more dispersed chromatin existed before. Whole chromosomes can be examined microscopically after breaking a dividing cell open and staining it with a suitable dye.

Не нашли, что искали? Воспользуйтесь поиском: