C. elegans

Question 1

Full scientific name for C. elegans

Answer 1

Caenorhabditis elegans

Question 2

Who invented C. elegans as a model organism (NP 2002)

Answer 2

Sydney Brenner (and H. Robert Horvitz and John E. Sulston)
"genetic regulation of organ development and programmed cell death"

Question 3

Is the genome sequenced?

Answer 3

Yes, first sequenced metazoan genome 1998

Question 4

Why study worms?

Answer 4

➢ Simple, but complex (adult worms 1mm long…1000 somatic cells all identified with function, neurons use same neurotransmitters as humans, they have all major tissue types humans have)
➢ Phylogenetically as close to humans as any invertebrate
➢ Nonparasitic (round worms, free living, eats E. coli)
➢ Rapid generation time (3.5 days @ 20 degrees, 2 generations a week)
➢ Transparent
➢ Stereotyped embryogenesis (cell division is same for each worm)
➢ Self-fertilization helps with maintaining stocks since a single animal can give rise to an entire population
➢ Cheap
➢ Genetics (great)
➢ Sequenced genome
➢ RNAi/CRISPR (these work well)

Question 5

Anatomy of hermaphrodite

Answer 5

pharynx, intestine, proximal gonad, uterus, distal gonad, anus

Question 6

What is a hermaphrodite?

Answer 6

female that can make sperm and self fertilize with that sperm

Question 7

If hermaphrodite has sperm from male and her own, male sperm is used __% of the time because ___.

Answer 7

99%, male sperm is bigger/more active

Question 8

Anatomy of male C. elegan

Answer 8

gonad, seminal vesicle, vas deferens, protoderm

*spikes on tail have neurons to sense hermaphrodites and for mating

Question 9

How to get male C. elegans?

Answer 9

@ 30 degrees for 6 hours…increase non-disjunction, will give stock with 50% males

Question 10

How to distinguish male and hermaphrodite worms

Answer 10

hermaphrodite tails are tapered and male tales are blunt with copulatory apparatus (spikes with neurons)

Question 11

Optimal growth temp for C. elegans

Answer 11

15-25 degrees, optimal 20 degrees for faster generation time

Question 12

Life cycle

Answer 12

Look at photo in slides

Question 13

If hermaphrodite vulva has mutation, it doesn’t develop properly and leads to ____

Answer 13

bag of worms (worms hatch inside mother then mother dies)

Question 14

Methods used with C. elegans

Answer 14

Positional Cloning by SNP Mapping: cross strain having lots of neutral polymorphisms (single base changes you can detect with restriction enzymes) with another strain with many differences, save DNA from cross and use different primers to look at SNPs

Whole genome sequencing: sequence a strain, look for changes

RNAi: inactivate any gene you want (inject dsRNA into gonad)

RNAi by feeding: engineer bacteria to make dsRNA and feed it to worms

Million mutant project: mutagenize worms then sequence genomes and isolate mutations in genes

CRISPR: easy in C. elegans for gene editing

Question 15

Transformation (transgene)

Answer 15

inject DNA into gonads, cells take up DNA and is incorporated into nucleus of developing gametes

ex. can cause worms to crawl in circles instead of crawling normally due to transgene

Question 16

Can c. elegans be frozen?

Answer 16

Yes! great for stock maintenance

Question 17

C. elegan use with mutations

Answer 17

used to identify mutations resulting in novel phenotypes (including conditional phenotypes) and mutations that modify existing phenotypes (can use fluorescent proteins to help)

Question 18

Disadvantages

Answer 18

• no C. elegan cell culture lines exist

- small size is a challenge since experimental manipulation in tissues of an organism <1mm is difficult

Question 19

History of research and key discoveries

Answer 19

The transparency of the animal allowed John Sulston, Robert Horvitz,
Judith Kimble, David Hirsh, and Einhard Schierenberg to describe every cell division starting with the single-celled
zygote and ending with the adult male and hermaphrodite

During this
same time, John White, Sydney Brenner, Donna Albertson,
Eileen Southgate, Sam Ward, and Nichol Thomson described the anatomy and connectivity of all 302 neurons of
the adult hermaphrodite