body plan control

Question 1

what is a body plan

Answer 1

the general structure of an organism with various body parts arranged in a particular way

Question 2

what controls the development of the body plan

Answer 2

proteins, setting up the right plan so everything is where it should be

Question 3

what genes code for the proteins controlling body plan

Answer 3

hox genes

Question 4

how do the hox genes work in fruit flies

Answer 4

two hox gene clusters control their body plan, one cluster controls the development of the head and anterior thorax whereas the other controls the development of the posterior thorax and the abdomen

Question 5

what is significant about the hox genes in fruit flies and other mammals

Answer 5

similar hox genes are found in humans and other mammals which means that body plan development is similar

Question 6

what are homeobox genes

Answer 6

regions of hox genes

Question 7

why are homeobox genes described as being highly conserved

Answer 7

sequences have changed very little during the evolution of organisms

Question 8

how do homeobox genes control development (3)

Answer 8

1. homeobox sequences code for a part of the protein called the homeodomain
2. the homeodomain binds to specific sites on DNA enabling the protein to work as a transcription factor
3. the proteins bind to DNA at the start of developmental genes, activating or repressing transcription and so altering the production of proteins involved in body plan development

Question 9

what is apoptosis

Answer 9

programmed cell death

Question 10

what are the stages of apoptosis (3)

Answer 10

1. enzymes inside the cell break down important cell components (DNA)
2. as cells contents break down it begins to shrink and breaks into fragments
3. cell fragments are engulfed by phagocytes and ingested

Question 11

what is the link between mitosis and apoptosis

Answer 11

mitosis and differentiation create the bulk of body parts and apoptosis refines the parts by removing unwanted structures

Question 12

how does the correct body plan develop due to mitosis and apoptosis

Answer 12

genes that control apoptosis and genes that control mitosis are constantly switched on and off

Question 13

how do the genes controlling mitosis and apoptosis respond to internal stimulus such as DNA damage

Answer 13

if DNA damage is detected by the cell cycle this can result in the expression of genes which cause the cycle to be paused and can even trigger apoptosis

Question 14

how do the genes controlling mitosis respond to an external stimuli such as stress

Answer 14

gene expression that prevents the cell undergoing mitosis

Question 15

how do the genes controlling apoptosis respond to external stimuli

Answer 15

genes are triggered when pathogen may enter the body