PPTH 115 Lecture 3-4: Molecular Properties

Viral genome

is the entire genetic make up of a virus

Nucleic acids

(DNA or RNA) make up the genome of a virus

1. RNA

2. DNA

Type of nucleic acid

RNA

majority (about 75%) of the plant viruses have (?) genome

1. Single stranded

2. Double stranded

type of strandedness

1. Positive sense

2. Negative sense

type of strand orientation

Positive sense

viral genome itself serves as the mRNA

Negative sense

viral genome has to be transcribed into mRNA

1. monopartite

2. Bipartite

3. tripartite

4. multipartite

number of nucleic acid molecules

monopartite

genome is composed of one nucleic acid molecule

bipartite

genome is divided into two segments, and each of these is packaged into a separate virus particle

RTBV

example of monopartite

begomovirus

example of bipartite

DNA A

functions required for DNA replication, control of gene expression, overcoming host defenses and encapsidation in begomovirus

DNA B

involved in intra- and intercellular movement in begomovirus

CMV

example of tripartite

RNA 1 & 2

involved in replication in cmv

RNA 3

movement protein and coat protein in cmv

1. Nanovirus

2. Babuvirus

example of multipartite

DNA-R

replication-associated protein (rep)

DNA-S

capsid protein (cp)

DNA-M

movement protein (mp)

DNA-C

cell-cycle link protein (Clink)

DNA-N

nuclear shuttle protein (nsp)

DNA-U3

unknown

1. Linear

2. Circular

Conformation of the viral genome

Genome size

refers to the total amount of genetic material (DNA or RNA)

contained within the genome of an organism or virus.

base pairs; nucleotides; kilobases (kb) or megabases (Mb)

Genome size is usually measured in (?) for DNA or (?) for RNA, and in the case of viruses, it can also be expressed in (?)

Phosphate+\text{Sugar}+\text{Base}=\text{Nucleotide}

The Structure of the Sequence

1. coding region

2. non-coding region

Viral genome structure

coding region

consists of viral genes that express the proteins

required for viral infection cycle

open reading frame

coding region represented as (?)

non-coding region

consists of nucleotide sequences with recognition and control functions important in virus replication

End structures

specialized structures at the 5’ and 3’ ends

Genome organization

is the arrangement of the coding and non coding regions in the genome

Coat proteins

facilitate virus transmission

polymerases

replicate the viral genome

proteases

process polyprotein into individual functional proteins

movement protein

facilitate virus movement

1. Structural

2. Non-structural/Functional

Viral Gene Products based on their role in the viral life cycle. It divides them into two main categories:

capsid

Structural

non-capsid

Non-structural

capsid

example of structural viral proteins

• Polymerase

• Movement protein

• Helper component

• Protease

examples of non-structural viral proteins