19.3 Body Plans

Question 1

What are homeobox genes?

Answer 1

genes responsible for the development of body plans

Question 2

What is the difference between hox genes & homeobox genes?

Answer 2

homeobox genes: encompass genes responsible for development of body plans

hox genes: specific homeobox genes present in animals for the correct positioning of body parts

Question 3

A homeobox is a section of DNA 180 base pairs long that is [highly/lowly] conserved between ____, plants & fungi.

Answer 3

highly, animals

Question 4

What are diploblastic organisms?

Answer 4

organisms which have 2 primary tissue layers

Question 5

What are triploblastic organisms?

Answer 5

organisms which have 3 primary tissue layers

Question 6

What are the different types of symmetry seen within body plans?

Answer 6

• RADIAL* - have no left or right sides, only top & bottom, found in diploblastic organisms
• BILATERAL* - have left & right sides rather than top & bottom
• ASYMMETRY* - no lines of symmetry, found in sponges

Question 7

How does mitosis & apoptosis control the development of body plans?

Answer 7

mitosis: proliferation of cells, to form a basic shape
apoptosis: removes unwanted tissues to shape the body part. Also releases chemicals which stimulate mitosis.

hox genes regulate both these processes

Question 8

19.3 Body Plans

What factors can affect the expression of genes involved in mitosis & apoptosis regulation?

Answer 8

• ENVIRONMENTAL FACTORS:
  
  • External - temperature, light
  • Internal - hormones, psychological stress

these factors have greater impact during growth & development of organism