BG4

Question 1

colonial and multicellular

Answer 1

colonial: multiple cells not specailised
multicellular: multiple specialsied cells

Question 2

evo of multicellularity in euraryotes

Answer 2

evolved 6x in eurkartores: animals. fungi, algae (RGB), land plants

Question 3

evo of multicellualrity volocine

Answer 3

shows a series of chomplexity from single cell chlamydomonas to gonium which is often a sheet to volox which is large with thousands of cells, inc. specailised germ and somatic

Question 4

myxcoccus

Answer 4

gram neg bacteria, feed on other bacteria in packs
food used up, they glide towards each other and form mounds of cells and fruiting bodies with specialised cells
most cells die, only few form myospores which germine anad undergo vegetative growth adn swam again

Question 5

Dictyostelium

Answer 5

multicellular slim mould
single cells live seperately in soil eating bacteria
when bacteria runs out, one of these cells releases cAMP which stimulates other cells to release it
this causes the cells to aggregate together and form a motile slug, slugs can join together or go through one another.
eventually the slug stops and produces a stalk witha fruiting body on the top.

Question 6

benefits of multicellularity

Answer 6

1. increase body size (anti-predation, economic benefits)
2. cell specialization
3. increased efficiency of coop feeding.

Question 7

costs of multicellularity

Answer 7

1. reduced growth rate (not all cells replicating)

2. cheating

Question 8

experimental evolution of multicellularity

Answer 8

take unicellular saccharomyces; grow in a shaking incubator, remove, allow to settle, select/pipette the yeast that has settled most quickly
- yeast that glom together settle faster
propogate each day

Question 9

experimental evo of multicellularity results

Answer 9

in 60 days get a multicellular snowflake phenotype
genuine multicellulairy with some cells being apoptosed to produce holes that give optimal biophysical structure such that they sink quickly.

Question 10

dictylostelium Hamiltons theory

Answer 10

stalk composed of 20% of cells - cells dont produce cells but die = hamiltons theory of altruism

Question 11

cheaters in dictylostelium

Answer 11

some genotypes evade forming stalks adn preferentially form spores that are dispersed.

Question 12

cheating mutations in dictylostelium

Answer 12

1. some eat other preventhing them becoming spores
2. some divide faster/inhibit division of others
3. some dont secrete cAMP
4. some ignore lateral signals specifying stalk

• some evidence cheaters become disproportionate lead to extinction as they fail to diversify and make slugs or pleiotropy prevents proliferation

Question 13

sponges avoiding invasion

Answer 13

evolved system of self and non self recognition

1. take three species of sponges rob
2. grind them into soup, sponges disintegrate into individual cells
3. then form species specific aggregates and reform into sponges.

Question 14

sponge aggregation factor

Answer 14

sponge self/non-self recognition is due to cell-suface glyconectin

• each AF i composed of many glycoproteins arranged in a sunburst configuration that bind to specific receptors on cell surface
• core proteins show distant homology to other cell membrane proteins but nothing like it is found in other metazoans

Question 15

examples AF

Answer 15

MAFp3 carrying g200 glycan

MAFp4 carrying a g-6 glycan

Question 16

ascidians

Answer 16

sponge like chrodates also compete for space, risk of invasion by conspecifics *(same species)

Question 17

ascidian conspecifics risk of meeting

Answer 17

either fuse or reject each other
fusion between two colonies of botryllus invader can replace not only somatic cells but germ cells of invadee, so propagates invaders germ cells

Question 18

fusion of ascidian

Answer 18

botryllus only fuses with genetically similar colonies

genetic recognition is regulated by fusion histocompatibility complex. FuHc locus

Question 19

FuHC`

Answer 19

highly polymorphic posses many codom alleles
colonies that guse have atleast one FuHC in common
colonies that reject each other have none.

Question 20

FuHC homology

Answer 20

hasnt been cloned yet

but thought to resemble MHC system

Question 21

cancers

Answer 21

cheater cells

mutations evolved leading to single cell clonal organisms,

Question 22

MHC

Answer 22

genes encode cell surface receptors that bind to foreign peptides and present them to T cells
many MHC genes, encoding proteins of several classes, some enormously variable with 100’s of alleles
enable distinguishment of self from not self

Question 23

MHC transplants and contagious cancers

Answer 23

MHC are the reasion behind trannsplant rejection and reason cellular rather than viral cancers arent contagious

Question 24

CVTS

Answer 24

canine venereal transmissible sarcoma.

1. cause via sex
2. originated 10,000 years ago from wold/husky like animal
3. LCA lived 500 years ago
4. host manipulation - infected dogs secrete for sex pheromone
5. suggetion evolved from myeloid cells possilbly macrophage lineage (can expression MHC classes)

Question 25

CVTS mitochondria

Answer 25

periodically acquired new mitochondria from hosts, multiple endosymbiosis events
perhaps because its clonal so mutations accumulate and disable mitochondria forcing it to get new ones

Question 26

sequenced cvts

Answer 26

1. massive copy no. variation
2. nearly 50% of genes have NS subs. - inc cancer genes myc, erg.
3. 3% of genes are disabled by mutation - presumably genes involved in multicellularity.

Question 27

immunosuppression strategies of ctvs

Answer 27

does not metastasize or kill host, regresses after a while
invasion phase has low MHC1 and 2 expression
secretes lots of TGF which inhibits host T-lymphocytes and NK cells
TGF also downregs MHC in both host and tumour

Question 28

DFTD

Answer 28

1. tasmanian devil
2. catch by scratching/fighting
3. transcriptomics show derived from schwann cell
4. karyotype of tumour cells is conserved by diverged from normal devil cells
5. driving devils to extinction

Question 29

features of animal multicellularity

Answer 29

1. specialisation of cell types - cell and tissue specific TFs
2. allorecognition and innate immunity - immune system molecules MHCs
3. regulated cell cycling and growth - cell cycle and genes and GFs
4. PCD - PCD pws.
5. cell/cell and cell/matrix adhesion – architectural elements
6. developmental signalling and gene reg/regional specificaiton via signalling molecules and regional TFs

Question 30

hamster transmissible cancer

Answer 30

1. reported in colony of syrian hamster, can be transmitted by mosquito A. aegypti bite

Question 31

human transmissible cancer

Answer 31

rare
malignant fibrous histiocytoma contracted from patient by surgeon when he injusred his hand during an operation.
though tumour escaped immune destruction via changed to MHC or abscence of immunogenic tumour antigens

Question 32

cross species cancer transmission

Answer 32

41 yearold man with HIV
tumour found to originate from dwarf tapeworm H. nana
parasite to host cancer transmission.
hypothesized mutation causing continued proliferation in immunosuppressed host allowed somatic mutations to occur in parasite stem cell population leading to malignant transformation

Question 33

bottlenecks and transmission

Answer 33

bottlenecks increase risk of cancer
loss of MHC diversity, higher risk of tumour transmissible tumours
both hamsters and devils tumours spread among animals with little gentic diversity
CVTV variants on the other hand evolved immune evasion enabling them to cross MHC barrier