isci test 4

virus

not (technically) living, affect all life groups

ubiquitous

can infect all taxonomic groups

rhinovirus, epstein-barr, HSV, HPV

most frequent infections for college students

bacteriophages

used as cloning vectorsc

cloning vectors

inserting a DNA sequence into a bacteriophage and it giving the DNA to bacteria to give it that gene

why are viruses necessary?

the dissipate dense populations and promote ecosystem diversity by making sure no one gets the upper hand and keeping growth logistic

small virus size

about 3-4 genes

large virus size

genome larger than that of bacteria

mimivirus

large virus example

how does viral disease happen?

replication within a host cell that either destroys or debilitates the cell and causes the immune system to overreact

what is special about HPV

can alter host genome and cause cancer

T2

what bacteriophage infects e Coli cells?

how do most phages infect cells?

by inserting their genome into the host cell and turning bacteria into "virus factories"

capsid

gets left outside of bacterial cells when virus infects them

phage genome

what directs the replication of virion?

void area of cells

how do we observe phages in a petri dish as a plaque?

measles

envelope is derived from host cell membrane

TMV

tobacco mosaic virus-- infects a wide range of plants and was the first virus ever discovered

how does TMV spread

it accumulates in high number within the cell then travels through interconnectionst

transmission

process of reaching and infecting a new host

droplets of respiratory fluid

how measles is transmitted

blood or sexual contact

how HIV is transmitted

more diverse and only have one type of nucleic acid (dna OR rna)

how are viral genomes different from cellular genomes?

RNA

type of nucleic acid in the coronavirus

capsid

protein coat viral genome is enclosed in

spike proteins

glycoprotein that connects membrane to capsid and is involved in binding to host cell

envelope outside capsid

not all have it, but it has viral proteins embedded and provide infection mechanism

RNA viruses

have higher error rate during replication

primates

host range for SIV

humans

host range for HIV and West Nile Virus

humans, birds, and pigs

host range for influeza

tissue tropism

range of tissue types a virus can infect (Ebola vs rabies)

surface receptor molecules

how tropism and host range are determined

why are viruses hard to treat?

-they have a relatively small number of virus-encoded proteins making medical therapy more difficult

• antivirals are hard to discover due to a lack of targets

• antivirals have side effects

• viral genomes mutate quickly within host (usually more than one drug needed)

• prevention is better than cure

lytic cycle

ends with bursting of the host cell

lytic cycle in depth

-phage attaches to host cell and inserts DNA -linear dsDNA cyclizes to circular DNA

• cell synthesizes capsid proteins

• cell replicates phage DNA and DNA is packaged into capsids

• phage lyses cell and progeny phages are released

lysogenic cycle

-phage DNA integrates into host cell genome to form prophage
- integrated phage DNA reproduces with host genome
-integrated phage DNA replicates with host genome or stress (temp or pH change) induces the decision of phage DNA and enters the lytic cycle

HPV

papillomavirus; infects 80% of adults and can cause cancer of cervix, penis, throat, and anus, HIGHLY contagious, has narrow tropism

gardasail

vaccine for HPV, only effective before exposure (by age 11-12) and protects against 4 strains including HPV-16

prions

infectious agent with no nucleic acid that comes from pre-existing cells

examples of prions

mad cow disease, scrapies, brain disease in sheep, kuru, abnormal form of normally occurring brain cell protein PrpC

PrpC

binds with normal form of protein and alters conformation in brain; forms harmful aggregates killing cell tissue (deterioration and dementia)

earth's composition

rocky sphere, covered 3/4 by water, thin layer of gases (atmosphere)

geology

broadest earth sciencec

crust

surface layer; thin and brittle

crust composition

rocks rich in silicon and oxygen

continental crust

granitic rock and deep roots-- most of it floats within the mantle and a small part is on earth's surface

oceanic crust

fine-grained basalt, higher proportion of iron and magnesium (darker and more dense)

isostasy

vertical positioning of earth's crust due to flotation in the mantle; reverse mass; why ancient sea creatures are embedded in basaltic rock high in the mountains

mantle

thick (middle) layer of hot rock, 82% of earth's mass, 2,900km thick

elements in mantle

silicon, oxygen, and proportionally more magnesium, iron, and calcium

why mantle has high density

pressure from surroundings increase density

core

huge ball of hot metal, 3500km thick, most knowledge comes from seismology

elements in core

mostly iron with some nickel

increases in concentric layers

how does density of earth increase?

112

number of elements in earth's layers; these elements are NOT distributed equally

8

number of elements earth is MOSTLY made of

near the center

heavy elements (nickel and iron) are concentrated...

at surface

lighter elements (silicon and oxygen) are more abundant...

how earth was formed

gravity, kinetic energy (molten rock, differentiation, cooling)

differentiation

gravity separates fluids according to densityc

cooling

hard rocks and liquid water formed

5

number of functional structural layers

lithosphere

shell of cool rigid rock, crust and upper mantle, 100km thick, thickest below continents, broken into pieces

tectonic plates

interlocking pieces of lithosphere

asthenosphere

under lithosphere, made of mantle rock; plastic

plastic

rock that is soft and flows very slowly

lower mantle

below asthenosphere, strong, rigid mantle (less plastic)

outer core

hot liquid metal (mostly iron, some nickel), spins as earth rotates, creates magnetic field, shields us from solar winds (GOOD)

inner core

solid sphere of hot metal (mostly iron) and 7000 degrees celsiuswh

pressure

what keeps iron in inner core from melting?

surface geology

largely determined by processes deep inside earth

alfred wegener

first discovered continental drift

pangea

mega-continentc

continental drift

world's continents move slowly over earth's surface

evidence of Pangea

-plant fossil found in India, South America, Africa, Australia, and Antarctica
-Mesosaurus reptile in Africa and south america
-rock matching evidence (africa and south america)
- evidence of glaciers on land near equator
-plate tectonics

land bridges

previous hypothesis for explanation of continental drift

ocean floor

NOT flat; canyons, trenches, mountain ranges, flat-topped volcanoes

mid-atlantic ridge

forms islands including Iceland; between americas and europe/ africa

rift

center of the ridge

youngest seafloor rocks

rocks of mid-ocean peaks

trenches

long, deep troughs in the seafloor found near continents and near bottom of oceanic volcanoes

seafloor spreading

new lithosphere is created at the mid-ocean ridge; when slabs slowly move apart, oceanic plates subduct below continental plates and are melted by magma

how are trenches formed

direct result of seafloor spreading

why wegener's hypothesis was incomplete

whole plates drift, not just continents

12

number of large pieces lithosphere is divided in

tectonic plates

100km thick, uppermost mantle and crust, ride on asthenosphere

2.5cm

how much plates move (in different directions and at different speeds) per year

plate boundaries

where the most intense geologic action occurs

what drives plates?

gravity, convection current, slab pulls

convection current

heat escapes the earth by rising and cycles through; bombardment and differentiation

divergent boundaries

neighboring plates move away from each other

effect of divergent boundaries

magma from asthenosphere enters widening gap (fissure or central vent)

East African Rift Zone

divergent boundary in the middle of a continentc

convergent boundaries

plates come together in slow moving collision

effects of convergent activity

destruction of lithosphere and subduction zones

oceanic-oceanic

older plate subducts, ocean trench, island arcs (HAWAII), parallel trenches, earthquakes

oceanic-continental

basaltic ocean plate subducts beneath continental, deep trench forms offshore, magma forms at subduction zone and erupts as lava, volcanic mountain chain (reason for mountains on west coast)

continental-continental

neither plate sinks below the other but instead push one another upward (HIMALAYAS- india rammed into asia 50 million years ago)

transform boundaries

plates slide past each other, lithosphere is conserved