Negative prefixes before adjectives
We can form the opposite of many adjectives or give the negative meaning by adding a negative prefix. These are the most common of them:
Dis-dissatisfied, discontinuous, disintegrated;
Il- illogical, illegal;
Im- immature, improbable, impure;
In-inappropriate, insufficient, inactive, insoluble, invisible, indirect, ineffective;
Ir- irregular, irrelevant, irreplaceable, irresponsible;
Un-unpreferable, uninfectious;
Non- non-transmissible, non-specific; non-existent, non-standard;
Mal- malnourished;
Ab- abnormal;
A-asymmetrical.
EXERCISES TO THE TEXT
Exercise 1. Look through the text. Which of the paragraphs deals with:
-covering over the nucleic acid?
-viruses that infect bacteria?
-lytic cycle?
- ways of transmission of a virus?
- symmetrical structures of capsid subunits arrangement?
- body defences against viruses?
- genetic material of a virus?
- definition of a virus?
Exercise 2. Give the definition of the following words.
1. Virus. 2. Capsid. 3. Lytic cycle. 4. Bacteriophage. 5. Icosahedral structure of a capsid.6.Lymphocytes. 7.Capsomer.8. Nucleocapsid. 9. Virion. 10.Core of the virus.11. Cell-preference of viruses.12. Helical structure of a capsid.
Exercise 3. Complete the following sentences. Choose the ending (or beginning) according to the text.
1. A virus is an infectiousagent of small size and simple composition that can multiply only in ... .
2. A nucleic acid genome is the core of the virus with … .
3. Capsid may contain enzymesthat enable the virus… .
4. Many viruses do not have the envelope and are called … .
5. The virus particles attack the cell and take over its machinery to carry out….
6. … enables the virus to survive outside the cell sufficiently long.
7. Viruses must first attach to a receptor on the … .
8. There are a few basic steps that all viruses follow infecting a host cell and these are called … .
9. Some viruses leave their genetic material in the host cell, where it can remain … .
10. Common viruses of the respiratory tract are usually …, and viruses of the digestive tract are often … .
11. A capsid is almost always made up of repeating structural subunits that are arranged in… .
Exercise 4. Choose the most appropriate word (or words) from those given in brackets.
1. A virus can (enlarge, multiply, increase) only in living cells of animals, plants, or bacteria. 2. The DNA or RNA (holds, accommodates, maintains) all of the information for the virus. 3. Many viruses do not have the envelope and are called (defenseless, nude, bare, naked) viruses. 4. The particles of the virus created by the cell come together to form new viruses. This is called (assembly, gathering, congregation). 5. When a virus enters the body, it (stops, releases, triggers) the body’s immune defences.6. Most viruses (kill, infect, contaminate) only one or a few species. 7. Each virus has its (specific, independent, isolated) receptor.
Exercise 5. Re-read the text to find out which of the following statements are correct.
1. Viruses are cellular organisms.
2. A nucleic acid genome of the virus contains both the DNA and RNA.
3.A virus particle has two main parts.
4. There are non-parasitic viruses.
5.Sometimes the capsid is surrounded by an additional spiky coat called the envelope.
6.Viruses are transmitted in a variety of ways, depending on the body system affected.
7.The body doesn’t have anyphysical barriers of defences against viruses.
8.The genomes of viruses can be comprised only of single-stranded DNA or RNA.
9.The distribution of the receptor molecules on host cells determines the cell-preference of viruses.
10.Sometimes, the infected cell loses control over normal cell division and cancer cells are produced.
11.Bacterial viruses are nonspecific to species of bacteria.
Exercise 6. Translate the following words and phrases into English.
Геном, покрытый белковой оболочкой;квази-сферическая структура; внутриклеточный паразит; сердцевина вируса;частицы вируса; оболочка, покрытая шипами;внедрение внутрь клетки-хозяина;защитный барьер;одноцепочечная молекула ДНК;рецептор вируса;прикрепление вирусных частиц к поверхности;нуклеиновая кислота вириона;спиральный тип симметрии;свернутая спираль нуклеиновой кислоты;икосаэдрический тип симметрии;активизировать иммунитет.