the bilaterians: building a body

Question 1

bilateral symmetry

Answer 1

single line of mirror image symmetry

• seperates left and right hand sides of body
• anterior and posterior
• doral and bentral

Question 2

common characteristics of bilaterians

Answer 2

• well defined blocks of muscles for moevment
  -centralize nerve cords
• all have same set of genes to build bodies
  -specialize sense organs
• tuble like/through cut; seperate mouth and anus
  ‘triploblasts’

Question 3

william bateson

Answer 3

founder of genetics; discovery the anatomy of the acorn worm

• wanted to know how variation arose in species
• showed importance of inheritance with homeotic varians in flies

Question 4

homeotic variants

Answer 4

when an animal found with ‘one structure’ is replaced by another that is usually found in another body area (e.g. antenna growing where eye should be in a fly)

Question 5

bithorax

Answer 5

homeotic mutation in flies that caused wings to grow where they should not be

Question 6

homeotic genes

Answer 6

‘hox genes’ or ‘homeobox’
stretch of 180 base pairs
- control development (such as flys segments)

Question 7

mcginnis

Answer 7

discovered that other animals also have homeoboxes

Question 8

what do hox genes do

Answer 8

• act as postcodes that tell cell where to develop along head to tail axis
• are common to all bilaterians; same set of genets pattern head to tail axis

are the ‘developmental tool kit’

Question 9

fly embryos gene roles

Answer 9

• cells on bottom/ventral side form nerve ford (GENE sog)

- cells on top/dorsal side form epidermis (gene dpp)

Question 10

vertebrate embry genes

Answer 10

sog gene= chordin (dorsal side; nerve cord)

dpp gene= BMP4 (ventral side)

Question 11

flys vs veretbrates?

Answer 11

opposition gene orientations

the chordata phylym is specifically the ‘upside down one’

Question 12

further similarities of vertebrates and insects

Answer 12

same genes control development of a ‘pulsating muscular tube’

same genes control specification of ‘where eye will form’

Question 13

what genes did the bilaterian ancestor have

Answer 13

• genes for distinguishing dorsal from ventral
• distingushing left from right
• telling cells where to develop along head to tail axis
• telling cells where to develop into sense organs and internal structures

Question 14

non-bilaterians and hox genes?

Answer 14

• cnidarisn ahve most of them but not all
• some lack the toolkit genes (like sponges)
• choanoflagellates have many of them abset