Virsuses Flashcards
What is a virus?
viruses are noncelullar microbes.
is a genetic element that can multiply only inside a living cell.
viruses are not alive.
what is a virion?
structurally intricate extracellular form an encoded genome that allows virus to multiply.
the virion allows the virus to travel from one host cell to another
what is capsid?
is a protein shell that contains the viral genome.
what is a nucleocapsid?
the inner structure of nucleic acid plus capsid plus capsid protein in envelope viruses,
what is a lytic pathway?
the virus redirects the host cell’s metabolism from growth to support virus multiplication and the assembly of new virions.
what is bacteriophage?
Bacterial viruses.
what is a capsomers?
a number of individual protein molecules which the capsid is composed of.
do viruses carry metabolic processess?
No
what are the 5 steps of viral replication?
1 attachment
- penetration of viral nucleic acid
- synthesis of new viral nucleci acid and proteins
- assembly and packaging of new viruses
- cell lysis and release of new virions
what is maturation phase?
begins as newly synthesized viral genomes become packaged inside their capsids.
what determines host specifity?
attachment
what is a temperate virus?
a virus whose genome can replicate along with that of its host without causing cell death,
what is a virulent virus?
a virus that lyses, or kills, the host cell after infection
what are key differences between eukaryotic and bacterial viruses?
(1) the entire virion of eukaryotic viruses enters the host cell,
2, eukaryotic cells contain a nucleus, where many (but not all) viruses replicate,
(3) in some eukaryotic cells, membrane-bound “viral factories,” also known as viroplasms, form to increase the rate of virion assembly and protect the process from host defenses
how does the animal virus enter the host cell?
entry into a host cell generally occurs by fusion with the cytoplasmic membrane or by endocytosis
where does viral replication happen in animal cell?
nucleus
what is the lysogenic cycle?
- attachment and penetration are identical to virulent viruses.
2.
what are the outcomes of viral infection?
A virulent infection (or lytic infection) results in lysis of the host cell;
in a latent infection, the viral DNA exists in the host’s genome as a provirus
can convert a normal cell into a tumor cell,
MOLECULAR BIOLOGY AND DNA REPLICATION
WHAT IS A GENE?
the functional unit of genetic information.
WHAT IS A GENOME?
total complement of genetic elements.
WHAT IS THE FUNCTION OF THE DNA WHAT DOES IT CARRY?
WHAT IS THE FUNCTION OF RNA WHT DOES IT CARRY?
DNA carries the cell’s genetic blueprint .
RNA, produced in transcription, carries a copy of this blueprint.
WHAT IS A NUCLEOTIDE?
WHAT ARE THE THREE COMPONENTS OF NUCELOTIDES?
The monomers of nucleic acids.
has three components: a pentose sugar (either ribose in RNA or deoxyribose in DNA), a nitrogenous base, and a molecule of phosphate,
IS DNA DOUBLE STRANDED?
YES
DNA is double-stranded, the strands being held together by hydrogen bonds between the bases in the two strands
WHICH THREE CLASSES OF RNA PARTICIPATE IN PROTEIN SYNTHESIS?
MESSENGER RNA’s :
are single-stranded molecules that carry the genetic information from DNA to the ribosome.
TRANSFER RNA’s:
help convert the genetic information in the nucleotide sequences of RNA into a defined sequence of amino acids in proteins.
RIBOSOMAL RNA’s:
are important catalytic and structural components of the ribosome
WHAT IS REPLICATION?
During replication, the DNA double helix is duplicated. Replication is catalyzed by the enzyme DNA polymerase.
WHAT IS TRANSCRIPTION?
The transfer of genetic information from DNA to RNA
WHAT IS TRANSLATION?
The formation of a polypeptide using the genetic information transferred to mRNA by DNA is a process that occurs on the ribosome.
WHERE DOES REPLICATION TAKE PLACE IN EUKARYOTES AND PROKARYOTES?
EUKARYOTES: replication and transcription occur in the nucleus
WHAT IS A CHROMOSOME?
main genetic element in prokaryotic cell. containing all (or most) of the organism’s genes.
HOW IS A CHROMOSOME DIFFERENT IN EUAKRTOIC CELLS?
are composed of two or more chromosomes containing linear DNA.
WHAT IS A PLASMID?
are circular or linear double-stranded DNA molecules that replicate separately from the chromosome and are typically much smaller than chromosomes.
WHAT ARE SOME FUNCTIONS OF PLASMIDS?
plasmid genes may encode enzymes for some special metabolism that ensures survival under certain conditions.
WHAT IS A SEMICONSERVATIVE REPLICATION?
the two resulting double helices each consist of one new strand and one parental strand.
WHAT IS A DNA POLYMERASE? what are its functions?
Enzymes that catalyze the polymerization of deoxynucleotides
function to repair damaged DNA
ARE REUIRED FOR DNA REPLICATION.
what is a template strand?
DNA strand that is used to make a complementary daughter strand
how does DNA replication proceed?
DNA replication always proceeds from the 5′ end to the 3′ end,.
WHAT ARE THE STEPS IN THE CIRCULAR DNA REPLICATION?
1, DNA begins from the origin
what is transcription?
RNA synthesis off of a DNA template—yields three main forms of RNA: messenger (mRNA), transfer (tRNA), and ribosomal (rRNA)
what are the functions of messenger (mRNA), transfer (tRNA), and ribosomal (rRNA)?
mRNA encodes genetic information from the genome for the synthesis of proteins and carries this information to the ribosome.
rRNAs play both a structural and a functional role in ribosomes.
tRNAs function as the carriers of amino acids to the ribosome for protein synthesis.
what is the three key processes of macromolecules?
(1) DNA replication; (2) transcription (RNA synthesis); and (3) translation (protein synthesis).
what is translation?
mRNA being translated into proteins.
what are the three types of proteins?
Catalytic proteins, structural proteins, and regulatory proteins.
what is the structure of DNA?
the backbone of DNA is deoxyribose-phosphate. The bases in DNA are: Adenine Guanine Cytosine Thymine
what are some of the characterirstics of DNA?
double stranded helical complementary hydrogen bonded antiparallel
what is supercoiling?
essential in DNA packaging
controlled by enzymes called topoisomerases
where is DNA stored in cells?
DNA is stored in plasmids or the chromosome.
what are the properties of chromosomes?
main genetic element
typically the largest genetic element
what are the properties of plasmids?
extra chromosomal replicates seperately smaller than the chromosome circular non essential genes
describe the process of DNA replication?
-semi conservative
-occurs in the 5’ to 3’ direction
begins at the origin of replication
occurs at replication forks
-bidirectional
-mediated by enzymes called DNA polymerases
describe the process of DNA repliocation in prokaryotes
- origin binding protein DNAa binds to the origin of replication, opens the DNA
- helicase unzips the DNA strand unwinds the helix
- single strand binding protein binds to binds to the single stranded DNA to stop it from binding together again.
what are some characteristics of RNA transcription?
charcteristics of RNA : single stranded similar to DNA except: uracil is used as a nitrogenous base sugar is ribose instead of deoxyribose -complementary to DNA template
what are the steps in Transcription?
initiation
elongation
termination
what is the bacterial ribosome and its functions?
the function is to bring mRNA and aminoacyl tRNA.
catalyze the formation of peptide bonds between amino acids and during translation and elongation.
what are the three sites in the bacterial ribosome?
A site: initial codon recognition site, accepts incomin charged tRNA
P site: hold tRNA bound to the growing peptide chain.
E site: exit site for uncharged tRNA
what is the DNA binding protein and its role?
THE GENE: -promoter -structural gene -transcriptional terminator ROLES: -process of transcription -regulation of transcription
what is the interactions of proteins with nucleic acids?
The interaction of proteins and nucleic acid are central to translation, transcription and replication.
what are the types of protein and nucleic acid interaction?
-specific
-non specific
R amino acid groups interact with nitrogenous bases of nucleic acid.
DNA interactions happen in the major groove.
what is the structure of DNA binding protein?
-helix-turn-helix
the first helix is recognition helix that interacts specifically with DNA
the second helix:
stabilizing helix stabilizes the first helix.
what are the reasons for transcriptional regulation?
increase effiecicy of use of cellular resources.
transcription is the first step in information flow.
amount of mRNA generally corelates to the amount of protein present.
what are transcription factors?
how do they function?
1, DNA binding proteins that control the rate of gene transcription
function:
-bind to promoter regions of DNA
-alter RNA polymerase interactions with promoter regions
-activators: increase rate of transcription
-repressors: decrease rate of transcirption
module 10 mutations
what is Mutation?
is a heritable change in the base sequence of that genome, a change that is passed from the mother cell to daughter cells.
what is genotype?
the nucleotide sequence of its genome
what is phenotype?
the observable properties of a mutant.
MODULE 11-13
WHAT IS DNA SEQUENCING?
is the determination of the nucleotide sequence of DNA within a cell.
WHAT ARE THE GENOMES OF PROKARYOTES?
CHROMOSOMES-
most bacteria and archea have one chromosome.
some bacteria have TWO chromosomes.
Plasmids are found rarely.
WHAT ARE THE SIZES OF PROKARYPTIC GENOMES?
112kb smallest
16mb largest
3-4 mb for most bacteria
WHY ARE PROKARYOTES WITH SMALL GENES NOT FREE LIVING?
because they have very few genes to independently produce biomass
exist in endosymbiosis of animals
WHAT IS THE MINIMUM NUMBER OF GENES TO BE FREE LIVING?
200-300
WHY ARE PROKARYOTES WITH LARGE GENOMES FREE LIVING ?
they have enough metabolic capacity to produce core componenets of biomass.
they are found in most diverse environments.
WHAT ARE THE FUNCTIONS OF GENOMES?
DNA replication transcription translation energy generation signal transduction
WHY IS EVOLUTION OF EUKARYOTES MARKED WITH ENDOSYMBIOSIS?
PRIMARY ENDOSYMBIOSIS- association with bacteria lead to chloroplats and mitochondria
SECONDARYENDO SYMBIOSIS- assocoaition of other eukaryotes with green or red algea
WHAT IS THE GENOME STRUCTURE OF CHLOROPLASTS?
STRUCTURE:
100-200 KB IN SIZE LINEAR OR CIRCULAR MULTIPLE COPIES PER CHLOROPLAST CONTENT: 6 rRNA COPIES tRNA genes chloroplast RNA polymerase RuBisCO gene
WHAT IS THE GENOME STRUCTURE OF MITOCHONDRIA?
STRUCTURE: 10-13 KB CIRCULAR MAY CONTAIN PLASMIDS CONTENT: 1 SET OF rRNA genes t RNA genes respiratory complext genes
WHAT IS THE SIZE AND STRUCTURE OF VIRAL GENOMES?
GENOMES OF VIRUSES CAN BE : DNA RNA SIZE: DNA (1.75KB TO 2.4 MB) RNA(1KB TO 50KB 2-40 GENES) MOST VIRAL GENOMES ARE SMALLER THAN BACTERIA.
WHAT TYPE OF BACTERIA VIRUSES ARE THERE?
bacteria viruses are DNA viruses class 1, 2 some RNA viruses class 3 and 4
WHAT TYPE OF ARCHEA VIRUS ARE THERE?
arechea virus are class 1 and 2 DNA viruses
what type of virus are eukarya?
RNA viruses 2 and 4
all classes can be found in animals
what is class 4 iv virus? structure? and lifecycle
class 4 of virus us poliovirus structure: ssRNA + naked virion lifecycle: attachment penetration in the cytoplasm synthesis assembly release
what is class V 5 of virus genome? structure and lifecycle?
RHABDOVIRUS STRUCTURE: helical symmetry, enveloped ssRNA- genome lifecycle: attachment penetration synthesis assembly release
WHAT IS CLASS 3 VIRUS III? structure and lifecycle?
class 3 virus is REOVIRUS
structure:
enveloped virus
dsRNA -,+
what is VI class 6 virus? structure and lifecycle?
class 6 virus is HIV
structure:
enveloped virus
ssRNA +
WHAT CLASS IS CORORNAVIRUS?
class 6 virus ssRNA+
WHAT IS VIRIOD AND PERION?
Viriods- are infectious RNA found in plants
Piriods- are infectious RNA found in animals
BOTH HAVE NO CAPSID
WHAT IS THE STRUCTURE, FUNCTION AND REPLOCATION OF VIRIODS?
STRCUTURE: circular ssRNA double stranded FUNCTION: infect plants through wounds replicate in cells disrupts plant development REPLICATION: replicated by host cell RNA polymerase
WHAT ARE PIRIONS, STRUCTURE AND FUNCTIONS?
STRUCTURE: proteins translated from host genes normal and misfolded FUNCTION: proteins have normal cell functions REPLICATION: replicated by host cells
